L

labeled 1. Carrying an identification of a recognized testing laboratory which certifies the results of appropriate fire tests conducted on essentially identical materials or construction, as a labeled door, labeled frame, or labeled window. 2. According to the NEC, materials or equipment carrying an identifying label, symbol, or other identifying mark of an organization that is acceptable to the authority having jurisdiction. The label indicates compliance with appropriate standards or performance in a specified manner.

labeled door A fire-rated door carrying a certified rating by the Underwriters’ Laboratories, Inc.

labeled frame A doorframe that conforms to all applicable requirements and tests of the Underwriters’ Laboratories, Inc., and bears their label.

labeled window A window that conforms to all applicable requirements, in respect to fire resistance, of the Underwriters’ Laboratories, Inc., and bears their label designating the fire rating.

label molding, label A square-arched dripstone or hoodmold; extends horizontally across the top of an opening and returns vertically downward for a short distance.

label stop 1. The termination of a hoodmold or arched dripstone in which the lower ends are turned away from the opening horizontally. 2. Any decorative boss or other termination of a dripstone, hoodmold, sill, etc.; a knee (Brit. colloq.).

labor and material payment bond A bond of the contractor in which a surety guarantees to the owner that the contractor will pay for labor and materials used in the performance of the contract. The claimants under the bond are those having direct contracts with the contractor or any subcontractor.

labor cost On a construction project, the cost of all labor necessary to produce the construction required by the contract documents.

laboratory fume hood Same as exhaust fume hood.

labyrinth 1. A maze of twisting passageways. 2. In medieval cathedrals, the representation of such a maze inlaid in the floor. 3. A garden feature of convoluted paths outlined by hedges, usually above eye level; also called a maze.

labyrinth fret, key pattern, meander A fret with many involved turnings.

lac A resinous insect secretion used as a base for shellac, lacquer, and varnish.

laced beam Same as lattice beam; see lattice girder.

laced column A composite column in which the components are connected by lacing, 1.

laced valley, woven valley A valley of a shingle, slate, or tile roof formed by interweaving shingles, slates, or tiles from the two intersecting surfaces.

lacewood A coarse-grained wood from Australia, pale pink to pinkish brown in color, moderately hard and heavy, with a lace-like figure; used for interior trim, paneling, and plywood.

lacework Architectural decorations resembling lace. Also see cast-iron lacework and jigsaw work.

lacing 1. A system of members (e.g., bars or batten plates) used to connect two component elements of a composite girder, strut, or column to make them act as one member. 2. Same as lacing course. 3. Timbers placed behind or around other supports as bracing. 4. Small boards which close up the spaces between lagging planks or sheeting to prevent dirt from entering an excavation. 5. The interlocking of sections of sheet pile to form a wall.

lacing course A course of brick or tile inserted in a rough stone or rubble course as a bond course.

laconicum The sweat room in a Roman bath.

lacquer Any glossy enamel which dries quickly by evaporation of the volatile solvents and diluents. Also see Chinese lacquer.

lacunar, laquear A coffer or coffering.

lacunaria The ceiling of the ambulatory around the cella of a temple, or of the portico.

ladder A frame, usually of wood or metal, consisting of two side pieces (called “stiles”) which are connected by crosspieces, usually round (called “rungs”); used as a means of climbing up or down.

ladder cable tray A continuous steel or aluminum support for wiring or cables.

ladder core A hollow core consisting of strips of wood, wood derivative, or insulation board, with the strips running either horizontally or vertically throughout the core area and with air cells and/or spaces between the strips; used as the core in interior doors.

ladder ditcher See ladder trencher.

ladder jack scaffold A light-duty scaffold supported by brackets attached to ladders.

ladder trencher A ditcher which digs trenches; utilizes buckets mounted on a pair of chains that travel on the exterior of a boom.

ladies’ room, women’s room In a public building, a room containing toilet and lavatory facilities for the use of ladies.

ladkin, latterkin A pointed piece of hardwood used for clearing out the grooves of the cames, which hold panes of glass in stained-glass windows and casements.

ladrillo In Spanish Colonial architecture and derivatives, an adobe brick that has been kiln-dried rather than sun-dried, thereby providing increased durability, increased mechanical strength, and greater moisture protection.

Lady chapel A major chapel dedicated to the Virgin Mary, on the axis of a church at its east end.

LAG On drawings, abbr. for lagging.

lag bolt, coach screw, lag screw A bolt having a square head and a thin, coarse-pitched thread.

lagged pile A pile having longitudinal pieces (i.e., lags) which are fastened to it for providing mechanical protection and increased friction and bearing area.

lagging 1. Thermal insulation for pipes, tanks, ducts, etc.; sometimes block insulation, pre-shaped to conform to the curved surface. 2. The planking, consisting of narrow strips, extending from one rib of the centering of an arch or vault to another; provides direct support for the voussoirs until the arch or vault is closed in. 3. Boards which are joined, side by side, lining an excavation. 4. Horizontal members between soldier piles. 5. Wood strips that cover a wall.

lag screw See lag bolt.

laid-dry masonry Same as dry masonry.

laid-on molding, planted molding A molding that is worked separately and fastened to the work by brads.

laid-on stop See stop, 1.

laitance The accumulation of fine particles on the surface of fresh concrete resulting from an upward movement of water in the concrete; occurs when excessive water is used in the mixing of the concrete.

laja In Spanish architecture and its derivatives, same as flagstone.

lake Any of a number of bright pigments which are prepared from animal, vegetable, or coal-tar coloring matter, or formed synthetically; used in paints.

lake sand Sand consisting mainly of rounded particles as contrasted with bank sand which has sharp edges; the latter is preferred in plastering.

Lally column A proprietary name for a cylindrical column which is concrete filled; used as a structural column to support beams or girders.

LAM On drawings, abbr. for laminate.

Lamassu The monumental human-headed, winged bulls that guarded the entrances to Mesopotamian palaces and temples.

lambert A unit of luminance equal to (1/π) candela per sq cm; equal to the uniform luminance of a perfectly diffusing surface emitting or reflecting light at the rate of 1 lumen per sq cm. Abbr. L.

Lambert’s cosine law A law stating that the luminous intensity, in any direction from a plane surface, varies as the cosine of the angle between that direction and the perpendicular to the surface.

lambrequin An ornamental horizontal band, often fringed, lobed, or notched along its lower edge.

lamb’s-tongue 1. The end of a handrail which is turned out or down from the rail and curved so as to resemble a tongue. 2. A carpenter’s molding plane having a deep and narrow blade more or less resembling a tongue and curved so as to cut a quirk bead. 3. A molding cut from such a plane, usually two ovolos separated by a fillet and set off by fillets at the other ends.

lamella A reinforced concrete, metal, or wood member joined with similar members in a crisscross pattern so as to form an arch or vault.

lamella roof A vaulted roof-framing system composed of lamellae.

laminar flow See streamline flow.

laminate 1. A product made by bonding together two or more layers of material, e.g., plywood, laminated wood, etc. 2. To unite layers of material with an adhesive.

laminated arch A wooden arch made of several layers or laminations of thin boards bolted or glued together.

laminated beam A beam built up by gluing together several pieces of timber; may be either straight or curved.

laminated glass, safety glass, shatterproof glass Two or more plies of plate glass, float glass, or sheet glass, bonded to a transparent plastic sheet between them to form a shatter-resisting assembly.

laminated joint A finger joint.

laminated plastic A plastic material consisting of superimposed layers of a synthetic resin-impregnated or resin-coated filler which have been bonded together (usually by means of heat and pressure) to form a single piece.

laminated timber See glued-laminated timber.

laminated wood Board or timber built up of plies which are joined together by gluing; usually the grain of all plies is parallel.

lamp A man-made light source which produces radiation in or near the visible region of the spectrum; often called a bulb or tube to distinguish it from the complete lighting unit consisting of the source and associated parts such as reflectors, etc.

lamp ballast See ballast.

lamp base, Brit. lamp cap That part of a lamp which connects to the lamp holder; provides electrical contacts.

lampblack, vegetable black A fine black pigment consisting of particles of carbon; collected from the soot of burning oil.

lamp bulb The glass envelope enclosing the luminous element or material of an electric lamp; usually made of glass, quartz, or similar material; its shape usually is designated by a letter (e.g., T—tubular, G—globe, etc.), followed by a number which indicates the maximum diameter of the bulb in eighths of an inch.

lamp cap (Brit.) See lamp base.

lamp depreciation The decrease in luminous output of a lamp during its operating life.

lamp holder, lamp socket A device which mechanically supports a lamp for the purposes of making electrical contact with the lamp.

lamp inrush current The initial surge of current when an incandescent filament lamp is turned on; may be as much as 50 times the rated current and may last several tenths of a second for high-wattage lamps.

lamp jacket The second, or outer, bulb used on some lamps.

lamp life See rated lamp life.

lamp lumen-depreciation factor The fractional loss of lumens radiated by a lamp at rated operating conditions; because of aging, this loss increases progressively during the lifetime of the bulb.

lamp post A standard support for a luminaire, provided with the necessary internal attachments for wiring and the external attachments for the bracket.

lamp socket See lamp holder.

lanai A living room or lounge area which is entirely, or in part, open to the outdoors.

lancet, lancet window 1. A narrow window with a sharp pointed arch typical of English Gothic architecture from ca. 1150 to ca. 1250. 2. One light shaped like a lancet window.

lancet arch A sharply pointed two-centered arch whose centers of curvature are much farther apart than the width of the arch; an acute arch.

lanceted Having a lancet window or arch.

Lancet style The style of Early English architecture distinguished by its use of the lancet arch; sometimes called First Pointed Gothic.

lancet window A narrow window having the shape of a lancet arch.

lanciform Having a sharp point.

land 1. Part of the surface of the earth not permanently covered by water. 2. Any immoveable improvements or fixtures attached thereto.

land boundary A line of demarcation between adjoining parcels of land. The parcels of land may be of the same or different ownership, but were distinguished at one time in the history of their descent by separate legal descriptions.

land-clearing rake A blade-like device which is attached to the front of a tractor; used to cut and collect brush which is removed in clearing a construction site.

land development The process of improving a large tract of land; includes clearing, grading, and the installation of sewers and utilities such as water, gas, and electricity.

land drain Same as agricultural pipe drain.

landfill The disposal of garbage, refuse, and trash by burying it under layers of earth in low ground or in excavated pits.

landing, pace, stair landing The horizontal platform at the end of a stair flight or between two flights of stairs.

landing door See hoistway door.

landing newel, angle newel A newel which is located on a stair landing or at a point where stairs change direction.

landing tread On a stair landing, the board directly over the uppermost riser; has an edge matching that of the nosing on the stair treads and has the same overhang.

landmark 1. Any building, structure, or place that has a special character, special historic interest, and/or special aesthetic interest, or value, as part of the development, heritage, or cultural characteristics of a nation, state, city, or town. 2. A monument, fixed object, or marker on the ground that designates the location of a land boundary. 3. A formal designation of such status for a building by a national or local authority. Also see National Historic Landmark and National Register of Historic Places.

landscape architecture The practical art and science of adapting land for human use and enjoyment, based on the premises that land use and beauty are compatible and that neither is complete without the other. Includes the planned combination of living plants, such as flowers, grass, ground cover, shrubs, trees, and vines, as well as natural features such as rocks and stones; and may also include reflecting pools, fountains, outdoor artwork, gazebos, screen walls, benches or fences.

landscaped roof A roof intended to be landscaped; the weight of the landscaping materials is considered to be a dead load, computed on the basis of the soil’s being saturated with water.

landscape improvement Any physical betterment of real property, or any part thereof, as a result of natural or artificial landscaping.

landscape screen See office landscape screen.

landscape window A double-hung window whose upper sash is decorated with small panes of colored glass; the lower sash, of clear glass, is a single pane and is larger than the upper sash.

land survey A survey of landed property establishing or reestablishing lengths and directions of boundary lines. Land boundaries are usually defined by ownership, commencing with the earliest owners through successive ownerships and partitions. Land surveying includes the reestablishment of original boundaries and the establishment of such new boundaries as may be required in the partition of the land.

land tie A tie rod or chain used to secure a retaining wall or the like.

land tile Porous clay tile pipe laid with butt joints.

land-use analysis The study of an existing pattern of use, within an area, to determine the nature and magnitude of deficiencies which might exist and to assess the potential of the pattern relative to development goals.

land-use plan The projection of a future pattern of use within an area, as determined by development goals.

land-use survey A study and recording of the way in which land is being used in an area; usually classified as commercial, industrial, public, residential, etc.

lane 1. A narrow passageway bordered by trees, fences, or other lateral barrier. 2. That part of a roadway which accommodates a single line of vehicles.

languet An ornamental band, often enriched, consisting of a series of upright, tongue-shaped elements.

lantern A windowed superstructure crowning a roof or dome; a lantern light.

lantern cross A cross atop a lanterne des morts.

lanterne des morts A graveyard lantern; a slender tower-like structure, usually in the form of a hollow column, terminated by a pierced turret containing a light which shone through the openings; many such towers were in France in medieval times.

lantern light A relatively small structure, having openings in its sides, above the roof of a building to provide light on its interior.

lantern skylight A small skylight atop a building to provide light and ventilation in the space below.

lantern-type chimney The top of a chimney shaft whose sides are pierced near the top to carry away the products of combustion, rather than their being carried away through the top of the chimney, which is covered.

lanthorne See cupola.

lap 1. To overlap or partly cover one surface with another, as in shingling. 2. The length of the overlap, as the distance one tile extends over another.

lap adhesive An adhesive used to seal the laps and sides of a jacket that surrounds thermal insulation around a pipe.

lap cement A type of asphalt used as an adhesive between the laps of roll roofing.

lap dovetail Same as lapped dovetail.

lapies A bedrock surface, beneath the soil, roughened as a result of action by a solution of limestone, gypsum, or other soluble rock; usually deeply trenched along joints. Such a bedrock presents hazards and results in excessive costs for footings and foundations.

lapis Same as milliarium.

lapis lazuli A rich blue semiprecious stone; either used decoratively or ground and powdered for use as an ultramarine pigment.

lap joint 1. A joint in which one board, plank, metal plate, etc., overlaps the edge of another piece; the overlapping part of each member is cut away to half thickness, resulting in flush surfaces. 2. A joint formed by placing one piece partly over another and uniting the overlapped portions.

lap notch Same as half-cut notch.

lapped dovetail, drawer dovetail A dovetail at an angle in which the pegs of one member do not pass through the full thickness of the other; esp. used at the front of a drawer.

lapped tenons Two tenons which enter a common mortise from opposite sides and overlap one another.

lappet One of a series of pendants trimming the eaves of a roof.

lapping In reinforced concrete, the overlapping of steel reinforcing bars, or other reinforcement, so there is continuity of tensile stress in the reinforcement when the concrete member is subjected to a flexural or tensile load.

lap-riveted Said of two plates overlapped and then joined by riveting.

lap scarf A flush joint formed by fitting one end of a length of wood gutter into the opposite end of another.

lap seam A joint formed by overlapping the edges of metal sheets or plates and joining them by riveting, welding, soldering, or brazing.

lap siding See clapboard.

lap splice 1. A connection of reinforcing steel made by lapping the ends of bars. 2. A splice made by placing one piece on top of another and fastening together with pins, nails, screws, bolts, rivets, or similar contrivances.

lap weld A weld in which the ends of the pieces are overlapped and then joined by welding.

laquear Same as lacunar.

lararium In Roman houses, a small shrine to the household gods (lares).

larch, tamarack A fine-textured, strong, hard, straight-grained wood of a coniferous tree; heavier than most softwoods.

larder A room where food is stored.

large calorie The heat required to raise 1 kilogram of water 1°C; equivalent to 1000 small calories or 1 kilocalorie.

large knot A knot in wood which is greater than 1½ in. (3.8 cm) in diameter.

larmier, lorymer 1. A corona. 2. Any horizontal member or stringcourse similar in profile to a corona and projecting from a wall to throw off rain; a roll molding, drip, etc.

larnite A mineral which is a major constituent of portland cement; beta dicalcium silicate.

larry A hoe having a long handle and a blade which usually is perforated; used for mixing mortar or plaster.

larrying, larrying-up In masonry construction, the laying of bricks by sliding the bricks into appropriate positions (for example, between the inner and outer walls of a cavity wall) and then filling the space between with mortar.

laser A device that emits a powerful beam of coherent light in an intense beam; used, for example, on building projects to provide a means of ensuring that construction is along a straight line, or to ensure that the construction is carried out to precisely the same height.

LAT 1. On drawings, abbr. for “latitude.” 2. On drawings, abbr. for “lateral.”

lat In Indian architecture, an isolated shaft or pillar serving various purposes, as for bearing inscriptions or religious emblems or for a statue or image.

latanier In the architecture of the southeastern US, palmetto fronds employed as a roof covering.

latch A simple fastening device having a latch bolt, but not a dead bolt; contains no provisions for locking with a key; usually openable from both sides.

latch bolt A spring bolt, one edge of which is beveled; when the door or window to which it is attached is closed, the bolt is forced inward; when in the fully closed position, the bolt springs back into a fixed notch or cavity.

latchet Same as tingle, 2.

latchkey A key used to raise and throw back the latch of a door.

latch plate An escutcheon that protects the area of a door around a latch.

latchstring A string for raising the latch of a door from the outside; it is fastened to the latch and passed through a hole above it in the door.

Late Georgian style See Georgian style.

Late Gothic Revival The last phase of the Gothic Revival in the early part of the 20th century, in which an attempt was made to emulate its Gothic architecture prototype with some degree of accuracy; for example, see Collegiate Gothic.

latent heat The amount of heat which is absorbed or evolved in changing the state of a substance without changing its temperature, e.g., in freezing or vaporizing water.

later A brick, formed in a mold and dried in the sun or baked in a kiln by the early Greeks and Romans; much larger and much thinner than modern bricks; each brick was stamped with the name of the maker and the year in which it was made.

lateral Same as lateral sewer.

lateral buckling, lateral-torsional buck

ling The buckling of a structural member which involves lateral deflection and twist.

lateral buttress A buttress that stands at one corner of a building.

lateral drift Same as drift, 1.

lateral load 1. See wind load. 2. See earthquake load.

lateral pressure The pressure, acting in the lateral direction, exerted by the retained soil against a structure.

lateral reinforcement That part of the steel reinforcement for a reinforced concrete column in the form of transverse hoops, links, or helixes around the vertical reinforcing steel rods.

lateral restraint The restraint that limits lateral movement of the compression flange of a beam.

lateral scroll A fitting which curves in a horizontal plane and is used to terminate a stair handrail.

lateral sewer A sewer which discharges into a branch or other sewer and has no other common sewer tributary to it.

lateral support The bracing for a wall, beam, or structural member, either horizontal (by roof or floor constructions) or vertical (by pilasters, columns, or cross walls).

lateral-torsional buckling See lateral buckling.

later crudus A brick baked in the sun rather than in an oven.

latericius Built of brick.

lateritum opus Brickwork of the ancient Romans.

Late Rococo See Neo-Rococo.

latest event occurrence time In CPM terminology, the deadline by which time an event must be completed if the project is not to be delayed.

latest finish date In CPM terminology, the latest point in time by which no further work must be done on an activity if the project is not to be delayed.

latest start date In CPM terminology, the latest possible point in time by which an activity must be started if the project is not to be delayed.

Late Victorian architecture A term occasionally applied to architecture in the Queen Anne style. See Victorian architecture.

latewood See summerwood.

latex An emulsion of finely dispersed particles of natural or synthetic rubber or plastic materials in water.

latex foam Sponge rubber made from latex.

latex mortar An admixture used as an ingredient in a batch of mortar-mix to retard its setting.

latex paint A paint containing latex in a water suspension (i.e., natural or synthetic rubber or plastic particles suspended in water) combined with pigments and other additives acting as binders.

latex patching compound A compound which consists of a latex (usually styrene-butadiene rubber), portland cement, and an aggregate; moisture-, mildew-, and alkali-resistant; used for patching or leveling a floor.

latex sealant A compound of latex which cures primarily through water evaporation.

lath A building material used as a base for the application of plaster; see expanded metal lath, gypsum lath, metal lath, split lath, wood lath.

lath brick A long, narrow brick.

lathe A machine for shaping circular pieces of wood, metal, etc., by rotating the material about a horizontal axis while a stationary tool cuts away the excess material.

lath hammer, lathing hammer, lathing hatchet A hammer which has a small hatchet blade on the side opposite the hammer head; the blade has a small lateral nick for pulling out nails; esp. used for cutting and nailing wood lath.

lathhouse A structure made of laths or slats to shelter growing plants requiring shade and wind protection.

lathing 1. A quantity of laths. 2. The erecting or placing of laths.

lathing board See backup strip.

lathing hammer, lathing hatchet See lath hammer.

lath laid-and-set In plastering, a method of finishing the ceilings and partitions of houses with two-coat work, in which the first coat is called laying, and is often scratched with a broom.

lath scratcher A tool, made from pieces of wood lath, for scratching and roughening base-coat plaster to improve the bond of the next coat.

latia In Spanish Colonial architecture, one of a number of light, relatively straight saplings, usually about 3 feet (1 m) long, that has been stripped of its bark and laid across log beams (vigas) of a structure, either diagonally so as to create a herringbone ceiling pattern or laid at right angles to the vigas. A matting of reeds, placed over the latias, is then covered with a layer of tamped earth, dried mud, or adobe mixed with grass, to serve as a roof.

latia labrada A latia that has been split along its length; usually laid across vigas with its flat side down.

Latin cross A cross with the vertical bar substantially longer than the horizontal bar.

latitude 1. The perpendicular distance in a horizontal plane of a point from an east-west axis of reference. 2. In surveying, the north-south component of a traverse course.

latrina An ancient Roman term for a bath or place to wash, or a water closet in a private home.

latrine 1. A public toilet. 2. A privy.

latrobe A stove or heater set under a mantelpiece, heating the room by direct radiation and one or more rooms above by hot air.

latten An alloy of copper and zinc; yellow in color, resembling brass.

latterkin See ladkin.

lattice 1. A network, often diagonal, of strips, rods, bars, laths, or straps of metal or wood, used as screening or for airy, ornamental constructions. 2. A regular member triangularly braced, e.g., a lattice girder, a lattice truss.

lattice beam See lattice girder.

lattice boom A boom of lattice-type construction, usually fabricated of steel angles or tubing.

lattice girder, lattice beam An open girder in which the web consists of diagonal pieces arranged like latticework.

lattice molding A wood molding, rectangular in section and broad in relation to its projection, resembling the wood strips used in latticework.

lattice porch A porch enclosed by a lattice, usually of wood strips; provides limited privacy, yet permits breezes to flow through the porch.

lattice truss A truss consisting of upper and lower horizontal chords, connected by web members which cross each other; usually stiffened by joining at the intersections of the braces.

lattice window A window casement, fixed or hinged, with glazing bars set diagonally.

latticework Reticulated or net-like work formed by the crossing of laths or narrow, thin strips of wood or iron, usually in a diagonal pattern.

lauan See Philippine mahogany.

laundry chute, clothes chute A shaft for conveying soiled clothing, bed linen, etc., by gravity from an upper to a lower floor of a building.

laundry room A room equipped with one or more washing machines, washtubs, driers, ironing boards, etc., for household linen and/or personal effects.

laundry tray, laundry tub, set tub A deep wide sink or tub, usually of porcelain, slate, or soapstone; used for washing clothes, etc.

LAV On drawings, abbr. for lavatory.

lavabo In monasteries of the Middle Ages, a large stone basin from which the water flowed through a number of small orifices around the edges, for the convenient performance of ablutions before religious exercises or meals.

lavacrum A place for washing.

lavatory 1. A basin with water supply and drainage piping, for washing the hands and face; a washbasin. 2. A room containing a washbasin and a water closet, but not a bathtub; a “powder room.” 3. Same as toilet, 2 or water closet, 2. 4. A small stone basin with a hole at the bottom to carry off water through a drain beneath; usually placed near the altar in an ancient church; used by the priest for washing his hands.

lavra 1. A Greek Orthodox monastery. 2. In a monastery, an assemblage of cells for monks around a common center that contains a church and sometimes a refectory.

lawn 1. An open space of ground of some size, covered with grass and kept smoothly mown. 2. Same as gauze, 2.

lawn sprinkler system A system of devices, usually installed below ground level, to scatter or spray water droplets over a lawn, golf course, or the like.

law of reflection As applied to rays of light, sound, or radiant heat which strike a surface: the angle of reflection is equal to the angle of incidence, and the reflected and incident rays are in the same plane with a perpendicular to the surface.

lay bar A horizontal glazing bar.

lay board A board which is fixed on the rafters of a pitched roof to take the feet of the rafters, forming a subsidiary roof transverse to the main roof.

layer Same as course.

layer board Same as lear board.

laying See lath laid-and-set.

laying length The length of an installed pipeline, measured along its centerline.

laying off The elimination of roller marks or brush marks on a wet paint surface by the application of light brush strokes.

laying-off angles In surveying, rotating a level to measure the angle between two intersecting lines.

laying out The marking of a material, indicating where cuts are to be made, in preparation for work to be done.

laying to bond Laying all the bricks in one course without the use of a cut brick.

laylight A glazed opening in a ceiling to admit light (either natural or artificial) to a room below.

layout A plan showing a scheme for an arrangement of objects and spaces.

lay panel A wall panel whose horizontal dimension is greater than its vertical dimension.

lay-up 1. In reinforced plastics, the reinforcing material placed in position in the mold. 2. The resin-impregnated reinforcement. 3. The assembling of veneers for fabrication as plywood.

lazaret, lazarette, lazaretto, lazar house A segregated area for infectious medical patients, esp. for their quarantine.

lazy susan A circular, revolving shelf; sometimes used in corner kitchen cabinets.

lb Abbr. for “pound.”

L-beam A beam whose section has the form of an inverted L; usually placed so that its top flange forms part of the edge of a floor.

Lbr Abbr. for lumber.

LCL 1. Abbr. for light center length. 2. Abbr. for “less than carload.”

LCM Abbr. for loose cubic meter.

L&CM Abbr. for “lime and cement mortar.”

L-column That portion of a precast concrete frame composed of the column, haunch, and part of the girder.

LCY Abbr. for loose cubic yard.

LDG On drawings, abbr. for landing.

leaching 1. The process of separating a liquid from a solid (as in waste liquid) by percolation into the surrounding soil. 2. The process of allowing soluble nutrients to move downward and percolate through the surrounding soil.

leaching basin A drainage pit with sand and gravel sides constructed to allow water to dissipate.

leaching cesspool A cesspool, 1 in which the solids present are retained and the liquid seeps into the surrounding soil.

leaching field Same as absorption field.

leaching pit See leaching well.

leaching well, leaching pit A pit, or a receptacle having porous walls, which permits its liquid contents to seep into the ground, but retains the solids.

lead 1. One of the sections of a masonry wall built up at each corner; supports a line between them which serves as a guide for constructing the remainder of the wall. 2. (pl.) See leads. 3. A soft, malleable, heavy metal; has low melting point and a high coefficient of thermal expansion; very easy to cut and work.

lead bat See lead wedge.

lead burning The welding of sheet lead.

lead-capped nail Same as lead head nail.

lead chromate One of a series of opaque pigments, orange to yellow in color, with high tinting strength.

lead chrome green See Brunswick green.

lead-covered cable An electric cable which is provided with a covering of lead to exclude moisture and to provide mechanical protection.

lead damp course A damp course fabricated of sheet lead.

lead dot A device for fastening sheet lead to a stone surface.

lead drier One of many organic lead salts which are soluble in paints and varnishes; used to speed the drying and hardening of the oil vehicle.

leaded brass An alloy of copper and zinc to which lead has been added to improve machinability.

leaded glass See leaded light.

leaded joint A plumbing joint that is sealed by pouring hot lead around it.

leaded light A window having small diamond-shaped or rectangular panes of glass set in lead cames.

leaded zinc oxide One of a series of mixed white pigments consisting of zinc oxide and basic lead sulfate; used principally in exterior house paints.

leader 1. A downspout. 2. A duct for conducting hot air to an outlet in a hot-air heating system.

leader head, conductor head, rainwater head An enlargement or catch basin to receive rainwater from the gutter at the top of a leader.

lead flat A flat roof which is covered by lead sheet laid over boarding.

lead foil tape A tape, typically about ½ inch wide and 0.002 inch thick (12.5 mm × 0.05 mm), which is cemented to a window or panel to detect its breakage; forms part of an alarm circuit through which a small electric current flows. If the window or panel is broken, the tape is severed and the circuit is interrupted, thereby activating an alarm.

lead-free paint A paint which contains no white lead or similar lead compounds.

lead glazing A leaded light.

lead head nail A roofing nail having a plain shank; makes a leakproof joint when driven through a metal roof.

leading A method of setting small panes of glass in a window with cames fabricated of lead.

leading edge, lock edge, strike edge The vertical edge of a swinging door or window which is opposite the hinge edge.

lead in oil White lead ground in linseed oil; formerly in wide use, now replaced largely by titanium dioxide pigments.

lead joint A joint in a water pipe in which molten lead has been poured, as in a bell-and-spigot joint.

lead-lag ballast A ballast for two fluorescent lamps, one of which operates on leading current and the other on lagging current; tends to reduce the stroboscopic effect.

lead-lined door, radiation-retarding door A door which is lined internally with lead sheets to prevent the penetration of x-ray radiation.

lead-lined frame, radiation-retarding frame A doorframe internally lined with sheet lead to prevent the penetration of x-ray radiation; always used with lead-lined doors.

lead monoxide Same as litharge.

lead nail A nail for fixing a lead sheet to a roof. Such nails are often fabricated of a copper alloy.

lead naphthenate A liquid drier added to paints containing drying oils to promote rapid drying and hardening.

lead paint Any paint containing white lead.

lead pipe Pipe fabricated from 99.7 percent pig lead; various lead alloys are also available for special applications such as drainage. Lead pipes are interconnected by wiped joints, burned joints, or flanged joints.

lead pipe cinch An easy type of joint used in fabricating pipe from elongated sheets of lead. First, the lead sheets are formed in a cylindrical shape with a flat overlap perpendicular to the cylinder; then, the flat overlap is folded over and crimped, thereby forming a sealed joint.

lead plug 1. A small cylinder of lead which is forced into a hole in a masonry wall; serves as a point of attachment for a screw or nail driven into it. 2. A piece of lead between adjacent stones, for holding them together; formed by pouring molten lead in a groove cut in the jointing faces.

lead primer See red lead.

lead roof A flat roof covered with sheet lead.

leads Short lengths of electric conductors, usually insulated; usually used in the plural.

lead safe See drip sink.

lead-sheathed cable Same as lead-covered cable.

lead shield A type of anchor, for an expansion screw or bolt, which consists of a lead sleeve that surrounds it.

lead slate, copper slate, lead sleeve A cylindrical sleeve, formed of sheet lead or sheet copper, used around a pipe where it penetrates a roof to make the intersection watertight.

lead sleeve See lead slate.

lead soaker See soaker.

lead spitter A tapered connector between a lead gutter and a downpipe.

lead tack 1. A lead strip used to secure the free edge of flashing; one end of the tack is fixed to the structure and the other end is folded over the free edge of the sheet metal. 2. A rectangular piece of lead which is attached to a lead pipe and enables it to be secured to a wall or other support.

lead-up Same as starter frame.

lead wedge A tapered strip of lead used to secure a flashing to a masonry wall.

lead wing In patent glazing, a strip of lead around a pane of glass to secure it and to prevent the entry of water.

lead wool A wool-like material of fine strands of lead; sometimes used as caulking in pipe joints.

leaf 1. A hinged part; a separately movable division of a folding or sliding door. 2. One of a pair of doors or windows. 3. One of the two halves of a cavity wall.

leaf and dart, heart and dart In Greek architecture and derivatives, a pattern of alternating, conventionalized, deltoid and lanceolate leaves, usually applied to a cyma reversa.

leaf and square A small tool used by plasterers in ornamental work; has a leaf-shaped blade at one end and a rectangular blade at the other.

leak See sound leak.

lean clay A clay having low values of liquid limit and plasticity index.

lean concrete Concrete of low cement content.

leaning tower A tower, usually detached and slender for its height, which overhangs its base; the most famous example of such a tower is at Pisa, Italy, where the 179 ft (54.6 m) tower is 16.5 ft (5 m) out of perpendicular.

lean lime An impure lime; has lower plasticity than pure lime.

lean mix, lean mixture 1. A concrete or mortar mixture with relatively low cement content. 2. A plaster which is not workable.

lean mortar Mortar which is deficient in cementitious components; is sticky and adheres to the trowel; is difficult to spread.

lean-to A small extension to a building with a roof (having but one slope) whose supports lean against the building.

lean-to house A seldom-used term used for a saltbox house.

lean-to roof, half-span roof A roof having a single pitch, carried by a wall which is higher than the roof.

lear board, layer board A board which is fixed across the rafters to provide a bearing surface for a roof gutter lining.

lease A contract transferring the right of possession of buildings, property, etc., for a fixed period of time, usually for periodical compensation called rent.

leaseback See sale-and-leaseback.

leasehold A tenure by lease; real estate held under a lease.

LECA Abbr. for “light-expanded clay aggregate.”

Le Chatelier apparatus A device used in the testing of hydraulic cements to measure soundness, 2.

lecithin A liquid, obtained in refinement of soya beans or cottonseed; used in paints to promote pigment wetting and to control pigment settling and flow properties.

lectern In a church or lecture hall, a stand with a slanting top to hold a book, speech, or music at the proper height for reading.

lectorium The site in a Christian church where parts of the Scripture are read.

LED Abbr. for light-emitting diode.

ledge 1. A small projecting member or molding. 2. A wood member across a number of boards to hold them together. 3. An unframed member which stiffens a board, or a series of boards or battens. 4. See bedrock.

ledged-and-braced door A batten door with diagonal bracing to provide additional reinforcement.

ledged door Same as battened door.

ledgement table, ledgment table A band course, stringcourse, or belt course, usually molded; esp. one carried along the lower portion of a building.

ledger 1. In formwork, a horizontal member which is supported by hangers or by upright posts and carries joists. 2. A horizontal member which is housed in the studs of balloon framing and carries joists. 3. In scaffolding, one of the horizontal members fastened to uprights which support the put-logs and which are at right angles to the wall; they carry the boards on which the workmen stand. 4. A flat slab of stone, such as that laid horizontally over a grave.

ledger board 1. A ribbon strip. 2. One of a number of horizontal boards, joined by vertical supports, as in a fence.

ledge rock Same as bedrock.

ledger plate 1. Same as ledger strip. 2. Same as ledger, 1.

ledger slab A stone slab set flush in the floor of a church.

ledger strip 1. On a beam which carries joists flush with the upper edge of the beam (or girder), a strip of lumber which is nailed to the side of the beam (along its bottom edge), forming a seat for the joists and helping to support them. 2. A ribbon strip.

ledgment, ledgement A horizontal, decorative stringcourse of brick or stone.

left-hand door See hand.

left-hand lock A lock for use on a left-hand door.

left-hand reverse door See hand.

left-hand stairway A stairway having the rail on the left side, in the ascending direction.

legal open space An open space on a premise, such as a yard or court that is permanently dedicated to public use, and that abuts the premise.

leg drop A narrow curtain, usually hung as one of a pair, on each side of a theater stage, parallel to the footlights.

legget, leggatt A tool used by reed thatchers to align the reeds.

legitimate house A theater in which stage plays are produced professionally.

lehr A long tunnel-shaped oven used in annealing glass, usually in a continuous process.

Leipzig yellow See chrome yellow.

leisure stairs Stairs having an unusually small slope.

LEMA Abbr. for “Lighting Equipment Manufacturers’ Association.”

lemon spline A strip of wood or metal, shaped like a slice of a lemon, which is inserted in a slot formed by two members, each of which is grooved and butted against the other.

lengthening joint Any joint (e.g., a halved, lapped, or scarfed joint) used to increase the length of a timber.

lens 1. A glass or plastic having smooth, regular opposite surfaces, shaped to control transmitted light by refraction; used in a lighting unit to focus, disperse, or collimate light rays. 2. A combination of such elements.

lens panel, lens plate A transparent material in which an array of individual lens elements has been formed; covers lamps in a luminaire to control the direction of emitted light.

leopardwood Same as letterwood.

leper’s squint See low-side window.

Lesbian cyma A cyma reversa.

Lesbian leaf Same as water leaf, 2.

lesche In ancient Greece, a public portico, clubhouse, or the like, frequented by the people for conversation or the hearing of news; such buildings were numerous in Greek cities, and their walls often were decorated by celebrated painters.

lesene See pilaster strip.

lessee The person receiving a possessory interest in buildings, property, etc., by lease.

lessor The person granting a possessory interest in buildings, property, etc., by lease.

let in In joinery, to insert, to embed, or to house; to secure a timber by inserting it in another.

let-in brace A diagonal brace that is let in to a stud.

letter agreement, letter of agreement A letter stating the terms of an agreement between addressor and addressee, usually prepared to be signed by the addressee to indicate his acceptance of those terms as legally binding.

letter box Same as mail box.

letter-box backplate A plate, attached to the interior side of a door, which permits the passage of mail but conceals the opening in the letter-box plate.

letter-box hood Same as letter-box backplate.

letter-box plate, letter plate A plate, attached to the exterior side of a door, having an opening through which mail may be passed; often has a letter-box backplate.

letter chute See mail chute.

letter-drop plate A letter-box plate, often with a letter-box backplate.

letter of intent A letter signifying an intention to enter into a formal agreement, usually setting forth the general terms of such agreement.

letter plate See letter-box plate.

letter slot See mail slot.

letterwood, leopardwood, snakewood A mottled wood of Guiana; has high elasticity; used for decorative veneer.

letting of bid See bid opening.

levecel An appentice.

level 1. A surveying instrument for measuring heights with respect to an established horizontal line of sight; consists of a telescope and attached spirit level, a rotatable mounting, and a tripod. Also see wye level and dumpy level. 2. The position of a line or plane when parallel to the surface of still water. 3. See spirit level. 4. Of an acoustical quantity, 10 times the logarithm (base 10) of the ratio of the quantity to a reference quantity of the same physical kind.

level control A series of bench marks or other points of known elevation, established throughout a project.

leveling 1. In paints, see flow, 3. 2. A surveying procedure of determining the difference in elevation between two points by means of a level or transit and a leveling rod. A spirit level is used on the level or transit to establish a horizontal line of sight.

leveling coat A thin coat of plaster to provide a level surface.

leveling course See asphalt leveling course.

leveling device On an elevator car, a mechanism which automatically controls the movement of the car near a landing so that the car stops at the landing.

leveling instrument An instrument to determine the differences in elevation between points.

leveling plate A steel plate placed atop a foundation on which a structural column may rest.

leveling rod, leveling staff A straight rod or bar, designed for use in measuring a vertical distance between a point on the ground and the line of collimation of a leveling instrument which has been adjusted to a horizontal position; usually made of wood and has a flat face which is graduated in terms of some linear unit and fractions thereof, the zero of the graduations being at one end of the rod; may have the graduations on a metal face. On some rods the graduation marks are designed to be read by the observer at the leveling instrument; another type, a “target rod,” carries a target which is moved into position according to signals made by the man at the instrument; when the target is bisected by the line of collimation, it is read by the rodman.

leveling rule A very long level, used by plasterers to indicate whether any part of a horizontal surface is higher than another.

leveling staff See leveling rod.

level surface A surface which at every point is perpendicular to a plumb line or the direction in which gravity acts; parallel to the surface of still water.

level transit Same as level, 1.

lever arm In a structural member, that length of the member between the center of the tensile reinforcement and the center of action of the compression.

lever board Same as louver board.

lever handle In builders’ hardware, a horizontal handle for operating the bolt(s) of a lock.

lever shears See alligator shears.

lever tumbler A flat tumbler in a lock; has a pivoted motion which is actuated by the turning of the key, thereby controlling the lock.

lever-type operator In a casement window, a substitute for a roto operator.

Levittown In the years following World War II, a bedroom community built in suburban New York City, eventually becoming one of the most successful garden communities of its type and often replicated; characterized by winding streets and affordable houses, each on its own site and having an attached carport.

lewis Any of several metal devices used in hoisting stone blocks, columns, or other heavy masonry units; consists of a dovetailed tenon, made in sections, which is fitted into a dovetailed recess cut in the masonry unit.

lewis bolt 1. A bolt with a wedge-shaped end inserted like the shank of a lewis in a hole drilled in a stone and fastened therein by pouring melted lead or concrete into the unfilled part of the hole. 2. An eyebolt similarly inserted and used like a lewis for lifting heavy stones.

lewis hole A dovetailed recess which is cut in a masonry unit for the reception of a lewis.

lewising tool A masonry chisel used for cutting lewis holes.

LFT Abbr. for “linear foot.”

LG On drawings, abbr. for “long” or “length.”

lgr In the lumber industry, abbr. for “longer.”

lgth In the lumber industry, abbr. for “length.”

LH On drawings, abbr. for “left hand.”

L-head The top of a shore which is formed with a braced horizontal member projecting on one side, forming an inverted L-shaped assembly.

liability insurance Insurance which protects the insured against liability on account of injury to the person or property of another.

Liberty See Neo-Liberty and Stile Liberty.

library A place for maintaining a permanent collection of books for public or private use; in a home, usually consists of a single room, but in a public or private facility, may occupy an entire building.

LIC On drawings, abbr. for “license.”

license A written document authorizing a person to perform specific acts, such as the construction or alteration of a building, or the installation, alteration, use, and/or operation of service equipment therein.

licensed architect See architect, 2.

licensed contractor A person or organization certified by governmental authority, where required by law, to engage in construction contracting.

licensed engineer See professional engineer.

lich-gate See lych-gate.

lich-stone See lych-stone.

lien A right enforceable against specific property to secure payment of an obligation.

lien waiver See waiver of lien.

lierne rib In Gothic vaulting, any small subordinate rib which is inserted between the main ribs, more often as an ornament than for reasons of construction.

lierne vault A vault in which lierne ribs are used.

life cycle That period of time over which a building or piece of equipment can be reasonably expected to carry out its intended function.

life cycle cost The cost of a building or equipment (or the like) based not only on the initial expenditure, but also on its maintenance and operating costs over its entire lifetime.

life performance curve For a source of light, a curve showing the variation of some characteristic of the source throughout its lifetime (e.g., lumens vs. life).

lift shaft Same as elevator hoistway.

lift 1. An elevator used on the stage of a theater, in the orchestra pit, or on the apron. 2. British term for elevator. 3. A handle or projection from the lower sash in a hung window, used as a grip in raising the sash; also called a sash lift. 4. One of a number of frames of scaffolding erected one above another in a vertical direction. 5. The concrete placed between two consecutive horizontal construction joints; usually consists of several layers or courses. 6. In reinforced concrete construction, that portion of a wall, pier, abutment, etc., placed in a single pour. 7. The amount of grouting or mortar placed at a single time in a building structure. 8. In a multi-level excavation, a bench or step.

lift gate A gate that opens by moving in a vertical direction, in contrast to one that swings about hinges along one edge.

lift hole A small hole in a pipe or pipe section which is used to insert a device for handling the pipe.

lifting, raising In paints, the softening and swelling of a film of old dry paint when a new topcoat is applied over it.

lifting beam Same as strongback.

lifting pin A lewis.

lift joint The joint formed between two successive lifts, 5.

lift latch, thumb latch A type of door latch which fastens a door by means of a pivoted bar that engages a hook on the doorjamb; a lever which lifts the pivoted bar is used to unfasten the door. Also see Norfolk latch, Suffolk latch, thumb latch.

lift-off butt hinge A special type of butt hinge which has a pin permitting the door to be raised off the hinge.

lift-off hinge See loose-joint hinge.

lift platform Same as elevator car platform.

lift shaft See hoistway.

lift slab 1. A method of concrete building construction in which floor (and roof) slabs are cast, usually at ground level, and then raised into position by jacking. 2. A slab which is a component of such construction.

lift well British term for elevator hoistway.

ligger 1. A horizontal timber secured to uprights and supporting floor timbers, scaffolding, or the like; a ledger. 2. A long stick (often of willow) used along the ridge of a thatched roof. 3. A mortar board. 4. A board pathway over a ditch.

light 1. An aperture through which daylight is admitted to the interior of a building. 2. A pane of glass, a window, or a compartment of a window. 3. An artificial source of illumination. Also see ceiling light, dead light, divided light, dome light, elliptical fanlight, fanlight, lantern light, leaded light, pavement light, quarter-round light, semicircular light, semielliptical light, sidelight, skylight, sodium light, sunburst light, transom light. 4. A spirelight.

light alloy Any alloy of aluminum.

light bridge A bridge, 3, fixed or suspended above a theater stage, to which lighting equipment is attached and/or from which it is operated.

light bulb 1. Same as incandescent lamp. 2. See lamp bulb.

light-center length The distance between the center of the light-generating element of a lamp (e.g., the filament of an incandescent lamp) and an arbitrary point on the lamp base; for each type of lamp base, the reference point is defined by convention.

light control-console A console, 3, in an auditorium, usually with a view of the stage; used to control the lighting—in the auditorium and on the stage.

light court A recess formed by the outer walls of a building and used to provide light and air through windows to adjoining spaces within the building.

light dimmer Same as dimmer.

light-emitting diode A solid-state device (diode) that emits light of a single primary color, but in combination with other diodes can produce colors of any hue for use in signage. These devices, each of which is about one centimeter (half-inch), have a remarkably long life. Also called an LED.

lightfast Descriptive of paint or pigment which is color-stable when exposed to sunlight.

light filter A device for changing the magnitude and/or the spectral composition of the radiant light flux which is transmitted through it; designated as selective (colored) or neutral, according to whether or not the spectral distribution of the incident flux is altered.

light-gauge steel A cold-rolled steel product, commonly available in the shape of flat sheets, angles, or channels; often used to frame non-structural partitions.

light globe See globe.

light hard bricks Bricks that are not the hardest ones in a kiln; thus are less able to withstand changes in temperature than are hard-burnt bricks.

light-hazard occupancy An occupancy in which the quantity and/or combustibility of its contents is low; if a fire should occur, a relatively low rate of heat release is expected.

lighthouse A tall structure, such as a tower, with a powerful source of light on top; located on a seacoast or other water channel to provide guidance for mariners at sea. Lighthouses were important facilities in establishing seafaring commerce and continued to be influential until the latter part of the 20th century, when they were largely replaced by electronic guidance systems.

lighting 1. The various processes, systems, forms, and/or equipment used to provide light and illumination. 2. See accent lighting, cove lighting, etc.

lighting batten A batten, 9 for lighting equipment.

lighting booth A booth, usually with a view of the stage, where the light-control console is located.

lighting cost, cost of light In lamp evaluation, the cost of light rather than total system cost; commonly expressed as the cost per million lumen-hours; depends on lamp cost, operating energy cost, and lamp replacement cost.

lighting fitting British term for luminaire.

lighting fixture An electrical component used to hold a lamp, fluorescent light, or the like; often includes a shade or light reflector; may be entirely functional in appearance or decorative in design.

lighting instrument A luminaire, esp. one that is portable and can be aimed, focused, or adjusted, as in theater lighting.

lighting outlet An electrical outlet intended for the direct connection of a lampholder, a lighting fixture, or a pendant cord which terminates in a lampholder.

lighting panel 1. An electric panel containing fuses or circuit breakers used to protect branch circuits serving lighting fixtures. 2. A panel for switching or controlling lights and lighting circuits.

lighting panelboard A panelboard which has 10% or more of its overcurrent devices rated at no more than 30 amperes.

lighting track A special type of surface raceway with preassembled electrical conductors in an open U-track; designed so that a lighting fixture (equipped with a special connector) may be inserted into the open U-track; the fixture is then twisted 90° to make contact with the conductors on the track.

lighting unit A luminaire; esp. a portable luminaire.

light loss factor A factor used in calculating the illumination provided by a lighting system after a given period of time and under given conditions; includes the effects of temperature, voltage, ballast variations, dirt on luminaire surfaces, dirt on the room surfaces, maintenance procedures, and atmospheric conditions. There are two categories: losses which can be recovered by replacing old lamps or cleaning surfaces, and nonrecoverable losses, such as those due to component deterioration or uncontrollable voltage drops.

lightly coated electrode See coated electrode.

lightness The whiteness of a painted surface as measured by the amount of light reflected from it.

lightning arrester A device which is connected in an electric wiring system (usually between a line voltage terminal and ground) to protect the wiring system from damage from lightning or any other abnormally high surge of voltage.

lightning conductor, lightning rod A metallic cable or rod, running from the highest point on the roof of a building (and insulated from it) to the ground; protects the building, should lightning strike, by providing a direct path to ground.

lightning rod A rod-like electrical conductor attached to the highest exterior point of a building; provides a direct electrical path to the ground if lightning strikes the building, furnishing protection against lightning-induced damage; invented in 1752 by Benjamin Franklin, who established that lightning is an electrical phenomenon.

lightning shake Separation between annual rings of wood, caused by lightning damage to the tree cambium during growth.

light output The total rate of flow of light energy emitted by a luminaire, 1.

light output ratio The ratio of the light output of a lighting fixture to the total light output of the individual lamp it houses.

light pipe Same as lighting batten.

lightproof blind A vertically operable lightproof shade which travels in guides that are fixed to the window jambs; when in the down position, the window is eliminated as a natural source of light.

light reflectance See reflectance.

light-reflective glass See reflective glass.

light resistance The ability of a material, such as a plastic, to resist fading after exposure to sunlight or ultraviolet light.

light source A See standard source A.

light source B See standard source B.

light source C See standard source C.

light tormentor A vertical pipe at either side of a theater or auditorium proscenium, used for mounting lighting units.

light transmittance See transmittance.

lightweight aggregate Aggregate of low-bulk specific gravity, such as expanded or sintered clay, foamed slag, fly ash, exfoliated vermiculite; used as an ingredient in lightweight concrete.

lightweight concrete Concrete of substantially lower density than that made from gravel or crushed stone; usually made with lightweight aggregate or by injecting air or gas into the mortar.

light well A shaft within a building, open to the outer air at the top, used to admit daylight and air through windows opening onto the shaft.

lignin 1. An organic substance in wood that, with celluloses, forms the principal constituent of wood tissue. 2. A crystalline product recovered from paper pulp; used in the manufacture of plastics, as a binder in wood chipboard, and for anticorrosive coatings.

lignum In ancient Roman construction, a beam or timber in a building, generally applied to the tie beam of a roof.

limba A straight-grained, fine-textured wood of the limba tree; esp. used for paneling.

lime A white or grayish-white caustic substance, calcium oxide, usually obtained by heating limestone or marble at a high temperature; used chiefly in plasters, mortars, and cements. In the past, in many areas along the seacoast where limestone was scarce, seashells were heated to obtain lime. See also hydrated lime, hydraulic lime, mortar, shell lime, slaked lime.

lime-and-cement mortar Hydrated lime, lime putty, or slaked lime mixed with portland cement and sand; forms a cement mortar used in masonry and in portland cement plaster (stucco).

lime burning The calcining (heating) of lime.

lime concrete A concrete made from a mixture of lime, sand, and gravel, widely used before the lime matrix was replaced by portland cement.

limed rosin Rosin reacted with lime; used as a binder in paints.

lime glass A common form of glass; contains a high proportion of lime.

lime mortar A mortar made by mixing lime putty and sand; now little used because of its slow hardening.

lime paste Lime soaked with water to form a putty.

lime plaster A base-coat plaster consisting of lime and aggregate.

lime putty, plasterer’s putty A hydrated lime which has been slaked with sufficient water to form a thick paste; used in plastering.

lime rock A natural, consolidated or partially consolidated form of limestone; mostly of calcium carbonate, but containing some silica.

limestone Rock of sedimentary origin composed principally of calcite or dolomite or both; used as building stone or crushed-stone aggregate or burnt to produce lime.

limestone marble A re-crystallized limestone, including commercial marble; capable of taking a high polish.

limestone tuff A soft, easy-to-cut stone that cannot be polished; composed mainly of carbonic material.

lime-tallow wash A mixture of lime and water with tallow; used on roofs, walls, and other external surfaces.

limewash A mixture of lime and water; used to coat internal and external surfaces; a whitewash.

limewood See basswood.

limit control A safety device on a boiler, refrigerator, or air-conditioning system which shuts off the system and actuates alarms when unsafe conditions are detected. Also see limit switch.

limit design Structural design based on any chosen limit of usefulness, such as a plastic limit, stability limit, elastic limit, fatigue limit, or deformation limit.

limited combustible material A building construction material which does not comply with the NFPA definition of noncombustible material. The materials in this classification must not exceed a potential heat value of 3500 Btu per pound (8141 kJ/kg); in addition, they must comply with at least at least one other applicable requirements of the applicable NFPA standard.

limiter A special-purpose fuse (usually of high current-interrupting rating) designed to protect an electrical circuit or equipment from the effects of high available short-circuit current by limiting the amount of current permitted to flow through it.

limiting height 1. The maximum height of a building permitted by code. 2. The maximum height of a partition or wall that can be designed and constructed without exceeding the allowable deflection for a given design load.

limit of proportionality See proportional limit.

limit state A condition beyond which a structure is unfit to perform its intended function.

limit switch An electric switch, operated by a power-driven machine or by the movement of the car which it drives, which alters or controls the electric circuit associated with the machine, e.g., a switch which slows down and stops an elevator car or dumbwaiter car automatically at or near the top or bottom terminal landing; operates independently of the device which normally controls movement of the car.

limonite A naturally occurring mineral which is used in high-density concrete because of its high density and water content, making it effective in radiation shielding.

LIN On drawings, abbr. for “linear.”

linden See basswood.

line 1. A system of cables and/or wires (along with poles to support them) used for the general distribution of electricity. 2. A flexible cable, chain, rope, or the like.

linear diffuser, slot diffuser, strip diffuser An air outlet where the ratio of length to width of the outlet usually exceeds 10:1; the width of the outlet usually is not greater than 4 in. (10 cm).

linear dimension A dimension measured along a straight line.

linear light source A light source whose dimension along a line is significantly greater than its other dimensions as, for example, a line of fluorescent lamps.

linear packer An automatic refuse compactor similar to a carousel packer, but the bags, contained on a linear carriage, move along a straight line; especially suitable for use in very narrow locations.

linear plan A house plan that is either one room wide and two or more rooms deep, or one room deep and two or more rooms wide.

linear prestressing Prestressing as applied to linear structural members, such as reinforced concrete beams or columns.

linear-type heat detector In a fire detection system, a heat sensor that can be activated anywhere along its length; employs a heat-sensitive cable whose electrical conductivity depends significantly on temperature. (See illustration p. 592.)

lined eaves A board that lines the underside of a roof which projects beyond an exterior wall.

line drilling In rock excavation by blasting, drilling a series of closely spaced holes, about 4 in. (10 cm) apart, at the perimeter of the cut, so as to break the rock along a line.

line drop The decrease in voltage in the conductors of an electric circuit resulting from their resistance.

line level A special spirit level used in checking the floor of an excavation, in laying pipe, and for similar work; each end of the level has a hook, permitting it to be hooked over a horizontally stretched line; is especially light and short.

linenfold, linen pattern, linen scroll A form of carved paneling representing a symmetrical fold or scroll of linen.

line of collimation See line of sight.

line of levels In surveying, a continuous series of measured differences of elevation.

line of pressure A line indicating the points of pressure between the voussoirs of an arch or buttress.

line of sight, line of collimation The line extending from an instrument along which distant objects are seen, when viewed with the telescope or other sighting device. Also see sight line.

line of travel See walking line.

line pin In bricklaying, a steel pin used as a support for the line by which a bricklayer aligns his work.

line pipe A welded or seamless pipe, available with the ends plain, beveled, grooved, expanded, flanged, or threaded; principally used to convey gas, oil, or water.

liner 1. In fabrication of stone veneer (principally marble), stone bonded to the back of the thin facing sheets to add strength, rigidity, bearing surface, or depth of joint. 2. A tool used by painters. 3. A sleeve piece used in plumbing. 4. Same as jamb lining.

liner plate A prefabricated plate of stamped steel; has corrugations to provide stiffness; provided with flanges so that similar units can be bolted together to form a support system for a tunnel, shaft, or pit.

line voltage The voltage provided by an electric power line at the point of use.

LIN FT On drawings, abbr. for “linear foot.”

lining 1. Material which covers any interior surface, such as framework around a door or window, or boarding which covers the interior surfaces of a building. 2. Same as flue lining.

lining out Marking timber for cutting.

lining paper 1. A paper, usually waterproof, fastened to the studding of frame buildings before nailing on the weatherboarding; used under slates and shingles in roofing. 2. An undercoat paper, applied to a surface as a base for a decorative wallpaper.

lining plate In sheet-metal roofing, a metal strip which is attached to the eaves to secure the lower edge of the roofing sheets.

lining tool A slanting-edged tool used by painters in drawing lines.

link dormer A dormer which joins one part of a roof to another, or one which houses a chimney.

linked switch Two or more electric switches which are mechanically connected by operating arms or levers, so as to operate at the same time or in a desired sequence.

link fuse An exposed fuse which is mounted on electrically insulated supports.

linoleum A resilient floor-covering material made by combining an oxidized linseed-oil binder and ground cork and bonding to a burlap or canvas backing; relatively low in cost; has poor stain resistance and low abrasion and dent resistance.

linseed oil A commonly used drying oil in paints and varnishes. Also see raw linseed oil.

lintel A horizontal structural member (such as a beam) over an opening which carries the weight of the wall above it; usually of steel, stone, or wood. Also see door lintel, eyebrow lintel, fireplace lintel, splayed lintel, through lintel.

lintel block, U-block A concrete masonry unit having a single core with an open end; usually placed with its open end upright; such blocks form a continuous beam when filled with grout and proper reinforcement.

lintel course In stone masonry, a course set at the level of a lintel, commonly differentiated from the wall by its greater projection, its finish, or its thickness, which often matches that of the lintel.

lintol Same as lintel.

lip 1. A rounded overhanging edge or member. 2. See lip strike.

lip block In timberwork supporting an excavation, a short timber which is fixed to the top of a strut and which projects over a wale.

lip molding A molding resembling an overhanging lip; commonly used as a buttress cap or base molding in the Perpendicular style.

lippage A ragged appearance that occurs when the upper edges of adjacent stones are not laid at the same level.

lipping A strip of wood that covers the edge of a built-up door so that the joints between the core and veneer are not visible.

lip strike The projection from the side of a strike plate which the bolt of a lock strikes first, when a door is closed; projects out from the side of the strike plate to protect the frame. (See illustration p. 594.)

lip union A pipe union having a lip to prevent the gasket from being squeezed into the pipe.

liquefaction 1. The sudden, large decrease of shearing resistance of a cohesionless soil caused by a collapse of the soil structure, produced by shock or small shear strains, associated with a sudden but temporary increase of pore water pressures. 2. The process of transforming a soil from a solid state to a liquid state, usually as a result of increased pore pressure and reduced shearing resistance. For example, an action in which a soil deposit (e.g., loose sand) loses its shear resistance temporarily and takes on the character of a liquid; such action, for example, may occur during an earthquake.

liquid-ash removal system A system for the removal of molten ash (continuously or intermittently, as desired) from the bottom of a furnace, by a piping arrangement operated by compressed air.

liquid asphaltic material An asphaltic product so soft that its consistency cannot be measured at normal temperature by a penetration, 2 test.

liquidated damages A sum specified in a contract whereby damages in the event of breach are to be determined. In a construction contract, liquidated damages usually are specified as a fixed sum per day for failure to complete the work, 1 within a specified time. If set at a level consistent with a reasonable forecast of actual harm to the owner, liquidated damage clauses will be upheld and will preclude use of standards for computation of damages that would otherwise be imposed by law. If the amount prescribed for liquidated damages is unreasonably high, the provision will be denominated an illegal “penalty” by the courts and held invalid; in such case, damages will be determined pursuant to otherwise applicable rules of law.

liquid chiller 1. See compressor-type liquid chiller. 2. See absorption-type liquid chiller.

liquid drier See soluble drier; drier.

liquid-immersed transformer A transformer having its core and coils submerged in an insulating liquid such as oil.

liquid indicator A device, frequently combined with a strainer, located in the liquid line of a refrigeration system and having a sight port by which the liquid flow may be observed for presence of bubbles.

liquid limit The water content corresponding to the limit between the liquid and plastic states of consistency of a soil.

liquid line A tube or pipe carrying the refrigerant liquid from the condenser or receiver of a refrigeration system to a pressure-reducing device.

liquid-membrane curing compound A material, laid down in the form of a liquid, which acts as a sealant.

liquid petroleum gas See liquified petroleum gas.

liquid receiver A vessel permanently connected to a system by inlet and outlet pipes for the storage of (condensed) refrigerant.

liquid roofing A seamless roofing material, applied in liquid or semiliquid form, to produce a waterproof membrane.

liquid-volume measurement The measurement of grout according to the total volume of its liquid and solid constituents.

liquid waste The discharge from any fixture, appliance, area, or appurtenance which does not contain fecal matter.

liquified natural gas (LNG) A product of natural gas essentially consisting of methanes; stored under pressure to maintain its liquid state; used as a fuel for heating and cooking.

liquified petroleum gas (LPG) A petroleum derivative, primarily butane and propane, stored under pressure to maintain its liquid state; used as a fuel for heating and cooking.

L-iron Same as angle iron.

lisena A Romanesque pilaster strip.

listed Equipment, materials, or products included in a list published by an organization acceptable to the authority having jurisdiction; the organization is concerned with the evaluation and periodic inspection of production of listed items; a listed item must meet appropriate standards or must have been tested and found suitable for use in a specified manner.

listed building Any building designated as being of historic architectural interest by one of the many organizations dedicated to the preservation of historic architecture.

listel, list A fillet, 1.

listing The sapwood cut from the edge of a board.

lite Same as light, 2.

liter, litre A metric unit of volume equal to 1/1000 cubic meter; equal to 61.03 cubic inches.

litharge A yellow lead monoxide (a powder of lead oxide); used as a pigment, as a drier, and as a catalyst in paints. Also see massicot.

lithic Pertaining to stone.

lithopone A white pigment consisting of zinc sulfide and barium sulfate, having moderate hiding power; high-strength lithopone contains a higher percentage of zinc sulfide.

lithostrotum opus In ancient Greece and Rome, an ornamental pavement made of small, irregular places of stone, such as mosaic.

litmus An organic chemical indicator of acidity or alkalinity; is red in color for pH values below 4.5 and blue above 8.3.

litre A series of coats of arms of the pious founders of certain churches in the Middle Ages and the Renaissance.

little house An 18th-century euphemism for an outdoor toilet; a privy.

liturgical choir That part of a choir reserved for the clergy serving the church.

liturgically sited Said of a church that is laid out in plan so that the congregation faces toward Jerusalem.

live 1. Connected to a source of voltage. 2. Said of a room having an unusually small amount of sound absorption.

live boom A boom on a power that can be raised or lowered without interrupting the digging operation.

live edge The edge of a painted surface which can be blended with fresh paint without having the lap show.

live-front Descriptive of a piece of electric equipment which is so constructed that there are live parts which can be touched from the front of the assembly.

live knot See intergrown knot.

live load The moving or movable external load on a structure; includes the weight of furnishings of a building, of the people, of equipment, etc., but does not include wind load.

liveness The acoustical quality of a live room.

live part Any electric component or part which is designed to operate at a voltage different from that of the earth.

livering The thickening of paint or varnish to an unusable rubbery consistency.

live room A room characterized by an unusually small amount of sound absorption.

live steam Steam that has not as yet given up any of its energy and has not yet condensed, e.g., steam emerging from a boiler.

living area See dwelling unit.

living hall, living stair hall A large room at the entry to a house, especially in an elegant home; frequently contains an imposing staircase, fireplace, and seating area; often, simply called the hall; also see entrance hall.

living room A space in a dwelling for social use of the residents.

living unit A dwelling or portion thereof, providing complete living facilities for one family, including permanent provisions for living, sleeping, eating, cooking, and sanitation.

LL On drawings, abbr. for live load.

L&L Abbr. for “latch and lock.”

LL&B Abbr. for “latch, lock, and bolt.”

lm Abbr. for lumen.

LM On drawings, abbr. for lime mortar.

LNG Abbr. for liquified natural gas.

lng, Lng Abbr. for “lining.”

LOA On drawings, abbr. for “length overall.”

load 1. A force, or system of forces, carried by a structure, or a part of the structure. 2. Any device or piece of electric equipment that receives electric power. 3. The power delivered to such a device or piece of equipment. 4. The amount of heat per unit time imposed on a refrigeration system; the required rate of heat removal.

load balancing The pre-stressing of a beam or slab so that it is subject to zero bending movement under its service load.

load-bearing partition A partition capable of supporting a load in addition to its own weight.

load-bearing tile Tile, used in masonry walls, which carries superimposed loads.

load-bearing wall A wall capable of supporting an imposed load in addition to its own weight.

load-carrying band A flat piece of metal which is welded to a side or end of a grating panel, used in a cutout to transfer the load from unsupported to supported bearing bars.

load-deflection curve A graph in which increasing flexural loads on a beam are plotted along the vertical axis, and deflections resulting from these loads are plotted along the horizontal axis. See flexure.

loader A self-powered machine equipped with a front-mounted bucket and lift arms for pushing and raising a load of earth or other construction materials; usually mounted on wheels or crawler-track undercarriage.

load factor 1. In structural design, the factor by which a working load is multiplied to determine the design ultimate load. 2. In air conditioning, the ratio of the average load on a system to the maximum load capacity. 3. In plumbing, the percentage of the total flow rate (expressed in fixture units) which is likely to occur at any point in the drainage system; represents the ratio of the probable load to the potential load.

load factor design A method of structural design based on the use of a given working load times a multiple; also see limit design.

load-indicating bolt A special type of high-strength bolt having a small projection which compresses as the bolt is tightened; the amount of projection can be measured with a feeler gauge, thereby acting as a measure of the bolt tension.

loading cycles In structural design, the number of repetitions of load assumed to act on a structure during its lifetime; used as a criterion in determining the fatigue strength of the structure.

loading dock See loading platform, 1.

loading dock leveler An adjustable-level platform or ramp which facilitates the handling of goods or materials to or from trucks, at a loading dock or at pavement level.

loading dock seal A resilient pad around the door of a loading dock to provide a tight seal between the door and a truck which has backed into the loading dock.

loading dock shelter A waterproof canopy which extends out from a building to provide weather protection between loading dock doors and the opening of a truck.

loading door A theater stage door through which scenery, properties, and other equipment are moved.

loading gallery A narrow gallery above the fly floor (fly gallery) in the stagehouse of a theater.

loading hopper A hopper, 1 in which concrete or other free-flowing material is placed for loading by gravity into buggies, etc.

loading platform, loading dock 1. An elevated platform at the shipping or delivery door of a building or adjacent to the stage of a theater; usually at the same height as the floor of a motor truck or railroad car to facilitate loading or unloading. 2. A platform on a theater stage for storing counterweights, 2.

loading ramp A device or facility (hinged, mechanical or hydraulic) to provide for differences in the heights or to span gaps between a loading surface and a carrier.

loading shovel Same as loader.

load-transfer assembly A unit which is designed to link or support dowel bars in the desired position during concreting operations.

loam In building construction, a mixture composed chiefly of moistened clay, sand, and silt, or some mixture including these ingredients. Once used as a mortar when combined with lime, or used as a plaster with the addition of chopped straw.

lobby A space at the entrance to a building, theater, etc.

lobe A segment of a circle in tracery; a foil.

lobed arch A cusped arch.

local buckling The buckling of a compression element which may precipitate the failure of the whole structural member.

local lighting Lighting which illuminates a relatively small area without illuminating the general surroundings significantly.

local vent, local ventilating pipe A pipe on the fixture side of a trap through which vapor or foul air is removed from the room or fixture.

local vent stack A vertical pipe, to which connections are made from the fixture side of traps, and through which vapor and/or foul air may be removed from the fixture.

location block Same as setting block.

location plan Same as site plan.

location survey The establishment on the ground of points and lines in positions which have been determined previously by computation or by graphical methods, or by a description obtained from data supplied by documents of record, such as deeds, maps, or other sources.

lodged floor A floor that is held in place by its own weight.

lock A mechanical device that secures a door, gate, cabinet, or the like; may be operated by a key or by a dead bolt. The earliest door locks had a hardwood casing with working parts fabricated of metal; later, these were replaced by all-metal locks. A further significant advance in lock design was the invention of the pin-tumbler cylinder lock in 1848. Also see box lock, case lock, door lock, rim lock, stock lock.

lock backset The distance from the edge of a door to the center line of the lock cylinder.

lockband A course of bondstones.

lock bevel The direction in which a latch bolt is inclined.

lock block In a hollow-core flush door, a block of wood (the thickness of the door stile) to which the lock is fitted.

lock clip A flexible metal part which is attached to the inside of a door face to position a mortise lock.

lock corner A corner (as of a drawer) which is secured by an interlocking construction, such as a dovetail.

lock edge See leading edge.

locker A lockable cupboard for storage of personal property for protection from theft.

locker plant A public facility containing lockable cupboards rented for cold or frozen storage of privately owned food.

lock face The exposed surface of a mortise lock which shows in the edge of a door after installation of a lock.

lock faceplate Same as lock front.

lock front, Brit. forend On a door lock or latch, the plate through which the latching or locking bolt (or bolts) projects.

lock front bevel The angle of a lock front when not at right angle to the lock case, allowing the front to be applied flush with the edge of a beveled door.

locking device Any device used to secure a member, unit, or assembly in position, e.g., to hold a cross brace in scaffolding to the frame or panel.

locking stile See lock stile.

lock jamb See strike jamb.

lock joint See lock seam.

lock keeper The box on a doorjamb into which the bolt of a lock protrudes.

lock miter A miter joint having interlocking edges. (See illustration p. 598.)

locknut 1. A nut which is designed so that it will not come loose, locking in place when tightened. 2. A supplementary nut, screwed down on another nut to prevent it from shaking loose.

lock plate 1. Same as strike plate. 2. Same as box strike plate.

lock rail An intermediate horizontal structural member of a door, between the vertical stiles, at the height of the lock.

lock reinforcement A reinforcing plate attached inside of the lock edge or lock stile of a door to receive a lock.

lock reinforcing unit A metal device used in a metal door to contain and support a lock.

locksaw A compass saw with a tapering flexible blade; used for cutting the seats for locks in doors.

lock seam, lock joint A joint or seam in sheet-metal roofing; the two edges are bent over in the form of hooks which are inserted in each other; then they are dressed down to form a seam.

lock seam door A door which has its face sheets secured in place by an exposed mechanical interlock seam on each of its two vertical edges.

lockset A complete lock system including the basic locking mechanism and all the accessories, such as knobs, escutcheons, plates, etc.

lockshield valve Same as key valve.

lockspit A small cut with a spade, or a small open trench, to mark a line of work, as fencing or the like.

lock stile, closing stile, locking stile, striking stile The vertical structural member of a door (or a casement sash) which closes against the jamb (or mullion) of the surrounding frame; the side away from the hinges.

lock strike Same as strike plate.

lock-strip gasket, structural gasket A gasket in which the sealing pressure is produced by forcing a keyed lock strip into a groove in one face of the gasket.

lockup A building or room for the temporary detention of prisoners by police.

loculus In ancient tombs, a recess for a sarcophagus or cinerary urn.

locust, black locust, red locust Wood of the locust tree; coarse-grained, strong, hard, decay-resistant, and durable; used in construction, esp. for posts.

locutorium Same as locutory.

locutory A place for conversation; esp. the parlor of a monastic establishment.

lodge 1. A small house in a park, forest, or domain; a temporary habitation; a hut. 2. The meeting place of a fraternal organization. 3. A porter’s or gatekeeper’s house at the entrance to the grounds of an estate.

lodging chamber Same as bedroom.

lodging house A building containing rooms used or rented for sleeping purposes by two or more paying guests; the minimum and maximum numbers of rooms may be specified by the applicable local code.

loess A uniform wind-deposited accumulation of silty material having an open structure and relatively high cohesion due to cementation of clay or calcium-like material at grain contacts.

loft 1. Unceiled space beneath a roof, often used for storage. Also see attic, garret. 2. Upper space in a barn, e.g., cockloft, hayloft. 3. Upper space in a church or concert hall, e.g., choir loft, organ loft. Also see rood loft. 4. Unpartitioned space in a loft building. 5. In a theater stagehouse, the space between the top of the proscenium and the grid.

loft building A building, containing open, unpartitioned floor space, used for commercial or industrial purposes.

loft ladder A disappearing stair.

log cabin A general term often applied to two different types of dwellings, both of which are constructed of logs. A log cabin is constructed of straight, relatively smooth, round logs stripped of their bark and laid horizontally, one above the other, to form a structure. In contrast, a log house is constructed of logs that are hewn to form square timbers before they are assembled as a structure. The construction of these two types of dwellings differs with regard to the tools, skill, and time required for their construction. In both, the logs are notched or otherwise fastened together to prevent their spreading at the corners and to provide rigidity and strength, but in a log cabin the logs protrude beyond the joints; in the log house, the square-hewn timbers do not protrude beyond the joints. Log cabin construction requires only an ax, a minimum of skill, and a minimum of construction time. The walls are usually waterproofed by an infilling between the cracks, such as clay. Typically, both types have a pitched roof. The earliest log cabins in America usually consisted of a single room; they usually had a battened door, and where brick or stone was scarce, a clay-and-sticks chimney. Compare with log house; also see dogtrot cabin, double-pen cabin, notch, planking, saddlebag cabin, vertical log cabin.

log-cabin siding An exterior wood siding, used on a small structure, which gives it the appearance of having been constructed of logs.

loge 1. A box in a theater. 2. The front section of a mezzanine or lowest balcony in a theater; usually separated by an aisle and/or railing from the section behind it.

logeion, logeum The raised platform for the actors in the Hellenistic theater, corresponding to the modern stage.

loggia An arcaded or colonnaded porch or gallery attached to or contained within a larger structure; usually located in a prominent part of the building; open on at least one side to provide a protected outdoor sitting area, sometimes contains an upper story. (See illustration p. 600.)

log house A house constructed of squared timbers that have been hewn from round logs, thus requiring an adze and/or other tools to shape them; the timbers are laid horizontally and notched or otherwise fastened to prevent their spreading at the corners and to provide rigidity and strength, and do not protrude at the corners as they do in a log cabin. The house usually has a shingled, pitched roof; often a chimney on a gable-end wall. Compare with log cabin, which is much easier to build.

log notch See notch.

lolly column Same as Lally column.

Lombard architecture North Italian pre-Romanesque architecture in the 7th and 8th cent., during the rule of the Lombards, based on Early Christian and Roman forms.

Lombard style 1. A synonym occasionally used for the Italianate style. 2. A term once applied to Romanesque Revival, now usually called Richardsonian Romanesque style.

London stock brick Originally, handmade bricks produced in the vicinity of London, made on a “stock,” i.e., a block of wood that locates the mold on the mold table; now machine-made brick of a coarse-textured yellow.

long-and-short work In rubble masonry, quoins which are placed alternately horizontally and vertically.

long column A concrete column whose load capacity must be reduced, according to code requirements, because of its slenderness.

long float A float so long that two men are required to handle it.

long gallery A gallery in the upper stories of an Elizabethan or Jacobean manor house; often used as a promenade or family room.

long grip The grip of a bolt or rivet which is longer than five times its diameter.

long header A header which runs the full depth of a thick wall.

longhouse 1. A multifamily dwelling usually having a rectangular plan divided by a central aisle along the length. 2. A 20th-century term for a building that once provided both the domestic quarters for a family and housing for animals.

longitudinal axis An axis along the lengthwise direction of the figure or body, usually passing through its center of gravity.

longitudinal bar A steel reinforcing bar used in longitudinal reinforcement.

longitudinal bond A masonry bond in which occasional courses are laid with all stretchers; sometimes used in thick walls.

longitudinal bracing Bracing extending lengthwise of the structure, or parallel to its center line.

longitudinal joint Any joint which fastens two pieces along their length.

longitudinal reinforcement Steel reinforcement, 1 for concrete which is essentially parallel to the horizontal concrete surface, or to the long axis of a concrete member.

longitudinal section In graphic representation, a section, 1 taken along the longest axis.

longitudinal shear A shear, 1 which is parallel to the longest axis of a member.

long-life lamp Any lamp type having a design life longer than the conventionally set value for its general class; an incandescent lamp of this type provides lower luminous output than a standard lamp of the same wattage.

long nipple A nipple having a considerable unthreaded length.

long-oil alkyd An alkyd resin in which over 60% of the solids consist of an oxidizing oil; used for brushing enamels.

long-oil varnish See long varnish.

long-radius elbow An elbow, 1 having a radius larger than standard to reduce friction losses and improve flow characteristics.

long room Primarily in the 17th and 18th centuries, a room for social gatherings, usually attached to a tavern.

long screw A pipe nipple usually 6 in. (15 cm) in length, with one thread much longer than usual.

long ton The equivalent of 2, 240 lb (1,016 kg).

long varnish, long-oil varnish An oleoresinous varnish containing 20 to 100 gal oil per 100 lb (2 to 10 liter oil per kg) gum or resin; more durable, more flexible, less glossy, and softer than short-oil varnish.

lookout 1. A rafter or joist at the ridge of a roof that projects beyond an end wall of a building; may support the overhanging portion of the roof or cornice; also called a rafter lookout. 2. An elevated place or structure that provides a wide view for observation of the countryside, particularly against marauders.

lookout tower A belvedere.

lookum A small roof or penthouse used to shelter a wall crane, hoisting wheel, or the like.

loom See flexible nonmetallic tubing.

loom house Same as spinning house.

loop 1. A loophole. 2. A circuit vent.

loophole 1. See arrow loop. 2. In a fortification, one of a number of long, narrow slits in the walls, usually widening inward to permit small arms to be fired over a wide angle at an enemy. 3. Same as slit ventilator.

looping in A method of avoiding splices in residential electric wiring by carrying the conductor or cable to and from the outlet to be supplied.

loop vent 1. A vent arrangement for a group of plumbing fixtures; consists of a vent pipe which is connected to the waste or soil branch immediately before the first fixture of the group and immediately before the last fixture of the group; the two connections are then “looped” together and connected to the vent stack. 2. The same as a circuit vent except that it loops back and connects with a stack vent extension of the soil stack instead of a separate vent stack.

loop window A long, narrow, vertical opening, usually widening inward, cut in a medieval wall, parapet, or fortification for use by archers; an arrowloop. (See illustration p. 602.)

loose-box See box stall.

loose-butt hinge Same as loose-joint hinge.

loose core See strip core.

loose cubic yard (or meter) A unit to express the volume of loose material.

loose-fill insulation Thermal insulation in the form of granules, nodules, fibers, powder, flakes, or shreds; may be hand-packed, pneumatically placed, or poured into cavities or over supporting membranes. Also see granular-fill insulation.

loose grid In a theater stagehouse, a counterweight system using rope ties at the pinrail, instead of fixed counterweights.

loose insulation Same as loose-fill insulation.

loose-joint hinge, heave-off hinge, lift-off hinge, loose-joint butt A door hinge having two knuckles, one of which has a vertical pin (at its center) that fits in a corresponding hole in the other; by lifting the door up, off the vertical pin, the door may be removed without unscrewing the hinges.

loose-key faucet A faucet that can be opened only with a tool or special handle so as to prevent its unauthorized use.

loose knot A knot in wood which is not firmly in place and may fall out.

loose-laid membrane A ballasted roofing membrane that is only attached to the substrate along the edges and at penetrations through the roof.

loose lintel A lintel that is not attached to another structural member but is merely placed across an opening in a wall during construction to support the weight of the wall above.

loose material Soil or rock in a blasted, broken, or loose state.

loose molding A removable wood glazing bead.

loose-pin hinge A hinge having a removable pin which permits its two parts to be separated.

loose side, slack side The side of knife-cut wood veneer, next to the knife, which has numerous small checks as a result of the cutting operation.

loose stop A nailed-on or planted stop bead; a planted stop.

loose tongue 1. Same as cross tongue. 2. A spline in a spline joint.

loose-tongue miter A mitered joint having matching grooves into which a common key or tongue is fitted to align or strengthen the joint.

loricula Same as squint, 1.

lorymer A larmier.

loss of gloss A paint defect in which a dried film of paint loses gloss, usually over a period of several weeks.

loss of prestress In prestressed concrete, the reduction of the prestressing force which results from the combined effects of creep in the steel and creep and shrinkage of the concrete; normally does not include friction losses but may include the effect of elastic deformation of the concrete.

loss of use insurance Insurance protecting against financial loss during the time required to repair or replace property damaged or destroyed by an insured peril.

lost ground Soil which runs from outside to within an excavation, as around or through sheeting, or as a boil on the bottom.

lost-head nail A thin nail having a head only slightly larger than the diameter of the nail itself; usually nailed below the surface of the wood.

lot A parcel of land that is described on a recorded plat or by a survey.

lot depth The distance from the front of a lot to the extreme rear line of the lot.

lot front The boundary line of a lot that abuts a street, or, if it abuts more than one street, then the street designated by the owner.

lotiform Having the shape of a lotus bud or flower, as used in some Egyptian column capitals.

lot line The legally defined boundary or limit of a parcel of land.

lot-line wall A wall adjoining and parallel to the lot line, used only by the party upon whose lot the wall is located.

lotus capital In ancient Egyptian architecture, a capital having the shape of a lotus bud.

lotus column A column whose capital has the shape of a stylized lotus; see Egyptian Revival.

loudness The intensive attribute of an auditory sensation, in terms of which sounds may be rank-ordered on a scale extending from soft to loud; depends primarily on sound pressure, but also on the frequency and wave form of the sound stimulus; expressed in units called sones; 2 sones is just twice as loud as 1 sone.

loudness level Of a sound, the sound-pressure level of an equally loud 1,000-Hz pure tone, expressed in units called phons.

loudspeaker An electroacoustic device, used to radiate acoustic power in air, the acoustic waveform of the reproduced sound being essentially equivalent to that of the electrical input.

Louis XIV, Louis Quatorze style The style of the high Classical period in France under the rule of Louis XIV (1643–1715) in architecture, decoration, and furniture, culminating in the building of Versailles. (See illustration p. 604.)

Louis XV, Louis Quinze style The Classical and Rococo style in France under the rule of Louis XV (1715–1774) in architecture, decoration, and furniture.

Louis XVI, Louis Seize style The later Rococo and classicist phase of the 18th century in France under the rule of Louis XVI (1774–1792), terminated by the French Revolution.

Louisiana Vernacular architecture See French Vernacular architecture, Cajun cottage, Creole house.

lounge An informal sitting room, esp. in a hotel, theater, or institutional building.

louver 1. An assembly of sloping, overlapping blades or slats; may be fixed or adjustable; designed to admit air and/or light in varying degrees and to exclude rain and snow; esp. used in doors, windows, and the intake and discharge of mechanical ventilation systems. 2. A dome or turret rising from the roof of the hall of a medieval English residence, originally open at the sides to allow the escape of smoke from the open hearth below; also called a lantern. 3. In side openings of a belfry, one of many sloping overlapping slats with a fixed open-space between them; sound produced by bells in the belfry is transmitted through these openings to the surrounding area. (See illustration p. 606.)

louver board One of the narrow boards, placed at an angle, in a louver or louver window; also called a luffer board.

louver door A door containing a louver, usually with horizontal blades, providing for the passage of air while the door is closed. (See illustraion p. 606.)

louvered ceiling A ceiling system consisting of multicellular louvers which shield the light sources mounted above it.

louvered shutter See shutter.

louver shielding angle The angle between the horizontal plane of a louver grid and the plane beyond which the louver conceals all objects above it.

louver-type damper A damper, 1 having multiple blades which are mechanically linked so that they open or close simultaneously.

louver window 1. A window having louvers which fill all or part of the opening instead of glass. 2. An open window in the tower of a church.

louvre Same as louver.

low-alkali cement A portland cement containing a relatively small amount of sodium or potassium or both.

low-alloy steel Steel having an alloy content of less than 8%.

low bid A bid stating the lowest bid price, including selected alternates, and complying with all bidding requirements.

lowboy A type of trailer for hauling construction equipment, with reduced ground clearance that facilitates loading of machinery without an auxiliary ramp.

low-carbon steel Steel having a carbon content less than 0.20%.

low-density concrete Concrete whose oven-dry unit weight of less than 50 pounds per cubic foot (800 kg/m³).

low-emissivity glass, low-e glass 1. A glass that has a special thin-film metallic or oxide coating which allows short-wavelength energy of the sun to be transmitted into a building, but which prevents long-wavelength energy of the heating systems within the building from escaping to the exterior; thereby conserves heat energy. 2. Same as reflective glass.

lower lateral bracing Same as bottom lateral bracing.

lowest responsible bidder, lowest qualified bidder The bidder who submits the lowest bona fide bid and is considered to be fully responsible and qualified to perform the work, 1 for which the bid is submitted. In the case of private construction contracts, the decision as to the bidder’s responsibility and qualification usually is made by the owner and the architect. In public contracts, a decision disqualifying a low bidder may have to be made on a reasonable basis rather than an arbitrary one.

lowest responsive bid The lowest bid which is responsive to and complies with the bidding requirements.

lowest tender Same as lowest responsive bid.

low-hazard contents Building contents having such low combustibility that no self-propagating fire therein can occur.

low-heat cement, type IV cement A cement in which there is only limited generation of heat during setting, achieved by modifying the chemical composition of normal portland cement.

low-lift grouting In masonry wall construction employing hollow concrete blocks, a technique in which wall sections are built as high as 5 feet (1.7 m); then, the cells of the masonry blocks are filled with grout.

low-noise lamp An incandescent lamp having a special internal construction to minimize the generation of audible noise, esp. when operated on certain types of dimmers.

low-pressure boiler According to the ASME Boiler Code, a boiler whose maximum safe working gauge pressure for steam service is 15 pounds per square inch.

low-pressure laminate A laminate molded and cured in the range of pressures from 400 lb per sq in. (28 kg per sq m) down to and including the pressure obtained by the mere contact of the plies.

low-pressure mercury lamp A mercury-vapor lamp whose partial pressure during operation does not exceed 0.001 atmosphere; fluorescent and germicidal lamps are included in this category.

low-pressure overlay A thermosetting resin-impregnated, wear-resistant paper, often with a decorative wood-grain print which has been applied, under pressure, at a high temperature to plywood, fiberboard, particleboard, etc., usually at a pressure of 150 to 250 lb per sq in. (7.5 to 10.5 kg per sq m).

low-pressure sodium lamp A sodium-vapor lamp having a relatively low partial pressure; produces a deep yellow light that is essentially monochromatic; widely used where the color of the lighting is not important (as, for example, in lighted parking lots) because of its high efficacy.

low-pressure steam curing Same as atmospheric steam curing.

low relief Same as bas relief.

low-rise building A building that is usually no more than five stories high.

low-side window, leper’s squint, offertory window, squint A small low window, usually on the right side of the chancel, through which the altar may be seen.

low-silicon bronze See silicon bronze.

low steel A soft steel containing a small amount of carbon (less than 0.25%).

low-studded Having short studs.

low-temperature recovery The ability of a sealant to recover its original form at low temperature when the deforming load is removed.

low-temperature-water heating system Same as hot-water heating system.

low-velocity HVAC system A heating, ventilating, and air-conditioning system in which the velocity of air in the ductwork is relatively low, thus limiting the noise created by the airflow through it.

low voltage According to ANSI/IEEE standards, a nominal system voltage of 1000 volts or less.

low-voltage lighting control A system of switches, control transformers, relays, and auxiliary devices to control a number of lighting circuits remotely, from one or more locations.

low-water alarm In a system in which water is supplied to a building from a gravity tank, an alarm indicating that the pump supplying the tank has not activated at the low-water condition and that water in the tank is dangerously low.

low-water cutoff A device required by the ASME Boiler Code on any steam boiler that is automatically fired; prevents the continued firing of a boiler that contains insufficient water.

lozenge 1. A rhomb or, more rarely, a rhomboid; usually one of a series. 2. In a double lancet window, a small light which pierces the space between the heads of the two lancets. (See illustration p. 608.)

lozenge fret, lozenge molding A type of diamond fret. (See illustration p. 608.)

lozenge light One of many small diamond-shaped panes of glass used in leaded lights.

LP On drawings, abbr. for “low pressure.”

L&P Abbr. for “lath and plaster.”

LPG 1. Abbr. for liquid petroleum gas. 2. Abbr. for liquified petroleum gas.

LP gas Same as liquid petroleum gas.

L-plan A plan having the shape of a capital letter L.

LPS Abbr. for “low-pressure sodium.”

LR Abbr. for living room.

LS 1. Abbr. for “left side.” 2. Abbr. for loudspeaker.

L-shore A shore having an L-head.

LT On drawings, abbr. for light.

lucarne A small dormer window in a roof or spire.

lucome window A term once used for a window in the gable end of a house, usually providing light for a room in a loft or attic.

lucullite A variety of black marble used in ancient Roman construction; first brought to Rome from Assan on the Nile River.

luffer Same as louver.

luffer board Same as louver board.

luffing-boom crane A heavy-duty crane having a tower-mounted boom, 2.

lug 1. In electric wiring, a device for terminating a wire or cable; the lug is bolted to an electric terminal. 2. A small projection attached to any member or component for use in handling, assembling, or installing.

lug angle See clip angle.

lug bolt A round bolt to which is welded a flat iron bar.

lug sill A sill, 3, with its ends extending beyond the window or door and built into the masonry at the jambs.

lukovitsa In early Russian architecture, an onion dome.

lumber Timber sawn or split in the form of beams, boards, joists, planks, etc., esp. that which is smaller than heavy timber. Also see board, 1, dimension lumber, matched boards, and yard lumber.

lumber core, stave core Wood core consisting of narrow strips of lumber edge-glued together; usually held in place by veneer which is glued to both faces with the grain of the veneer at 90° to that in the core.

lumber grade A classification used by the lumber industry for pieces of lumber: the categories are standard, structural, and utility.

lumen (lm) The SI unit of luminous flux equal to the luminous flux received on a unit surface, all points of which are equidistant from a point source having a uniform intensity of 1 candela.

lumen maintenance curve See life performance curve.

lumen method, flux method A procedure in lighting design used to determine the number and types of lamps or luminaires required to provide a desired average level of illumination on a work plane; takes into account both direct and reflected light flux.

lumiline lamp A tubular incandescent lamp having a lamp base at each end.

luminaire 1. A complete lighting unit consisting of one or more lamps, together with components which are designed to distribute the light, to position and protect the lamps, and to connect the lamps to the electric power supply; also called a lighting fixture. 2. The above lighting unit without lamps in it. 3. A device that projects light on the stage of a theater.

luminaire classification 1. For indoor luminaires, a classification system based on the percentage of flux which is emitted by the luminaire, above (or below) a horizontal plane through the center of the luminaire. 2. Floodlights: a measure of the beam spread in terms of beam angle ranges: type I, beam angle 10° to 18°; II, 18° to 29°; III, 29° to 46°; IV, 46° to 70°; V, 70° to 100°; and VI, above 100°.

luminaire dirt-depreciation factor A factor (used in illumination calculations) which relates the initial illumination provided by a clean, new luminaire to the reduced illumination that it will provide as a result of the accumulation of dirt on the luminaire at the time when it is next scheduled for cleaning.

luminaire efficiency The ratio of luminous flux emitted by a luminaire to total flux emitted by the lamp or lamps in the luminaire.

luminance The luminous intensity of any surface in a given direction per unit of projected area of the surface, as viewed from that direction; a directional property of luminous radiation.

luminance contrast The relationship between the luminance of an object and the luminance of the immediate background.

luminance factor The ratio of the luminance of a surface or medium under specified conditions of incidence, observation, and light source to the luminance of a lossless, perfectly diffusing surface or medium under the same conditions.

luminance meter, brightness meter A visual instrument or a photoelectric instrument used to measure luminance.

luminescence The emission of light not ascribable directly to incandescence.

luminosity The ratio of luminous flux to the corresponding radiant flux at a particular wavelength; expressed in lumens per watt.

luminous ceiling A ceiling area-lighting system comprising a continuous surface of transmitting material (of a diffusing or light-controlling character) with light sources mounted above it.

luminous efficacy The ratio of the total emitted luminous flux, in lumens, to the total electric power consumption in watts.

luminous efficiency Same as luminous efficacy; also called the luminous coefficient.

luminous energy The time integral of luminous flux; given by the product of the luminous flux and the time that the flux is maintained, if the luminous flux is of constant value; usually expressed in lumen-hours.

luminous flux The rate-of-flow of radiant energy emitted by a lamp.

luminous intensity The luminous flux per unit solid angle in a specific direction from a point source of light; in practice, an interior source may be considered a point source if the distance exceeds 5 to 10 times the maximum source dimension of the luminaire; in US Customary units, expressed in candlepower; in SI units, expressed in candelas.