J

jacal 1. A rectangular structure, either partially enclosed or open on all four sides, used as a temporary storage place, such as for grain; usually a flat roof supported by two to four posts on each side of the structure (depending on its size) and often covered with a layer of adobe mud or straw. 2. In the American Southwest, a crude house having walls built of closely spaced upright sticks, or poles driven into the ground, and small branches interwoven between them; then covered with mud or an adobe clay; usually plastered to provide additional weather protection; a flat roof is supported by horizontal logs and then covered with thatching, often with a layer of adobe atop the thatching. 3. Same as wigwam.

jack 1. A portable machine, variously constructed for exerting great force for moving a heavy body through a short distance. Also see hydraulic jack; jackscrew. 2. An electrical receptacle into which a plug, 7 is inserted to make electrical contact between communication circuits.

jack arch Same as flat arch.

jack beam A beam that supports another beam and eliminates the need for a supporting column.

jack boom A boom which supports sheaves that carry lines to a working boom.

jacked pile A pile (usually sections of pipe spliced together) which is forced into the ground to a bearing stratum, jacking it against a building or structure above; used primarily for underpinning.

jacket 1. A metal or cloth covering over the heat insulation which is applied to exposed heating pipes and ducts. 2. An outer casing around a pipe or vessel, the space between being filled with a fluid for cooling, heating, or maintaining a fixed temperature.

jackhammer 1. An airhammer. 2. A hand-operated, pneumatic, rock drill.

jacking The imposition of a static driving force on a pile by the use of jacks; a technique widely used for installing piles in the underpinning of structures.

jacking device 1. A device used to raise a vertical slipform. 2. A device used to stress the tendons in prestressed concrete.

jacking dice In foundation work, blocks used as temporary fillers during jacking operations.

jacking force The force exerted temporarily by the device which introduces tension in tendons in prestressed concrete.

jacking plate A steel plate, atop a pile during jacking operations, which is used to transmit the load of the jack to the pile.

jacking stress The maximum stress occurring during the stressing of a tendon in prestressed concrete.

jack lagging The rough lagging, 2 in centering an arch or vault.

jack pile Same as jacked pile.

jack plane A carpenter’s plane, of medium size; used for coarse work.

jack post A post comprising two telescoping sections, so that it is adjustable in height; used to support a floor beam.

jack rafter Any rafter that is shorter than the usual length of the rafters used in the same building; esp. occurs in hip roofs.

jack rib Any rib in a framed arch or dome shorter than the others.

jackscrew A jack in which a screw is used for lifting; carries a plate which bears on the load.

jack shore A telescoping, or otherwise adjustable, single-post metal shore.

jack timber A timber in a framework which, being intercepted by some other piece, is shorter than the rest.

jack truss A roof truss which is smaller in size than the others, usually because of location, as in a hip roof.

Jacobean architecture An imprecise term, applied to an English architectural style of the early 17th century that adapted the Elizabethan style to continental Renaissance influences; applied to buildings erected during the reign of James I (1603–1625) and thereafter. Large houses were usually two to three stories high and might have elaborate multicurved Flemish gables, Tudor arches, and decorative chimneys, and casement windows (separated by stone or cement mullions) that had small, diamond-shaped panes of glass held in place by grooved strips of lead.

Jacobethan style, Jacobethan Revival A mode of Tudor Revival architecture, of limited popularity from the 1800s to about 1920, that was a blend of Jacobean and Elizabethan architecture; hence, the compound term. Such buildings are often characterized by front-facing gables that rise above the roofline; elaborate brickwork or stonework; quoins at the corners of the building; occasionally, turrets or towers; stone straight-line gables or multicurved gables, tall decorative chimneys; rectangular window frames, usually containing small, leaded panes of glass set in casement sashes.

jagging Notching or indenting, as on beams.

jail 1. A prison. 2. A building or place for the legal detention of persons.

jal-awning window A window having a number of top-hinged out-swinging pivoted sashes (ventilators, 2) one above the other, which are operated by one or more controls, with individually operated locking mechanisms.

jalousie A shutter or blind with fixed or adjustable slats which exclude rain and provide ventilation, shade, and visual privacy.

jalousie window A window consisting of a series of overlapping horizontal glass louvers which pivot simultaneously in a common frame and are actuated by one or more operating devices so that the bottom edge of each louver swings toward the exterior and the top edge swings toward the interior during opening.

jamb One of the vertical members at each side of an opening such as a doorframe, window frame, or fireplace.

jamb anchor A metal device inserted in the back of the jamb of a doorframe or window frame to anchor the frame to the wall.

jamb block, sash block A concrete masonry unit which has an end slot (rabbet) for use at an opening to receive a jamb.

jamb depth The overall depth of a door-frame, measured from one face to the other.

jamb entension The section of a metal door jamb which extends below the level of the finish floor for attachment to the rough floor.

jamb horn The part of the jamb of a window frame which extends beyond the sill or head jamb.

jamb lining 1. A strip of wood which is applied to the inside edge of a window jamb to increase its width. 2. Same as door case.

jamb post An upright timber at the side of an opening; a wood jamb.

jamb shaft A small shaft having a capital and a base, placed against or forming part of the jamb of a door or window; occurs mostly in medieval architecture. (See illustration p. 552.)

jambstone A stone which forms a jamb of a door.

jamb stove An 18th cent. cast-iron stove at the back wall of a fireplace; projects into and heats the room adjoining the back of the fireplace.

jam nut Same as locknut.

janua In ancient Roman architecture, a front door which opens on the street.

Janus Same as bifrons.

japan A short-oil varnish, usually dark in color, which produces a hard glossy surface.

Japanese architecture Architecture of timber construction exclusively, from the 5th cent. A.D. under the strong influence of China. Simple pavilion-like structures consist of a wooden framework of uprights and tie beams supported by a platform, with nonbearing plaster or wood panel walls, sliding partitions, and doors and windows of lightweight material—often paper. The tiled, hipped roofs are widely projecting and upward-turning, on elaborate bracket systems. Stone is used only for pillar bases, platforms, and fortification walls. Great emphasis is put on the integration of buildings with their surroundings, with verandas providing the transition. Proportions of floor dimensions, height, and length of walls follow fixed standards. Modern Japanese architecture, though under strong Western influence, has developed a reinforced concrete style of its own, steeped in its tradition of timber construction.

Japanese ash, tamo A light, yellowish wood having a grain similar to oak; esp. used for veneer.

Japanese lacquer See Chinese lacquer.

Japanese tung oil See tung oil.

jardin anglais Literally, an English garden, particularly popular in the 18th century.

jaspé Mottled and marbled to resemble variegated stone, and to mask signs of use; e.g., jaspé linoleum.

jawab A false building or structure which is constructed for aesthetic reasons, to achieve a desired balance or proportions.

jaw crusher A machine for crushing rock between two inclined jaws.

JB Abbr. for junction box.

JCT On drawings, abbr. for “junction.”

jealous glass Any nontransparent glass, for example, ground glass.

jedding ax A stonemason’s tool; a kevel, 1.

Jeffersonian Classicism See Classical Revival architecture.

jemmy Same as jimmy.

jenny A machine which shoots out a jet of steam; used for cleaning surfaces.

jerkinhead, clipped gable, hipped gable, shreadhead The end of a roof when it is formed into a shape intermediate between a gable and a hip; the gable rises about halfway to the ridge, resulting in a truncated shape, the roof being inclined backward from this level.

jerrybuilt Built in a flimsy manner.

Jerusalem cross A Greek cross with a smaller Greek cross inscribed in each of the four spaces between the arms.

Jesse window A painted window containing a decorative genealogical tree representing the genealogy of Christ.

jesting beam A beam introduced for the sake of appearance and not for use.

jettied house A house having an overhanging second story. See also garrison house.

jetted pile A pile which has been sunk by jetting.

jetting 1. The sinking of piles or well points by the use of a water jet, e.g., through a hole in a cast concrete pole or by inserting a pile in a hole produced by jetting; esp. used where pile driving may damage neighboring buildings. 2. The compacting of backfill around a pipe by introducing water under pressure in the trench in which the pipe is laid.

jetty A projecting part of a building, as a bay window or the upper story of a timber house.

jib 1. Of a crane or derrick, see boom, 2. 2. Same as gib or jib door.

jib boom A piece which extends the upper end of a boom, 2.

jib crane A crane having a swinging boom.

jib door, gib door A door which is flush with, and treated in the same manner as, the surrounding wall so as to be concealed; has no visible hardware on the room side.

jib window Same as jib door.

jig A device for guiding or holding a part or parts in correct mechanical alignment, either in the process of fabrication or in the final assembly of the parts.

jigger saw Same as jigsaw.

jigsaw An electrically powered saw having a narrow blade which moves with a reciprocating motion, in a vertical direction, through the surface of a table on which work is placed; esp. used for cutting curves and ornamental patterns.

jimmer See gemel.

jimmy, jemmy A short crowbar.

jinnie wheel Same as gin block.

jitterbug A tamper, usually pneumatic, for concrete.

job 1. Same as project. 2. Same as work, 1.

job captain A member of the architect’s staff normally responsible, on a given project, for the preparation of drawings and their coordination with other documents.

job site The site, 1 of a construction project.

job superintendent See superintendent.

jog Any irregularity in a line or surface.

joggle 1. A notch or projection in one piece of material which is fitted to a projection or notch in a second piece to prevent one piece from slipping on the other. 2. A stub tenon on the end of a timber which prevents the timber from moving laterally; also called a joggle joint, 2. 3. An enlarged area on a post to support the foot of a strut.

joggle beam A built-up beam, the parts of which are fixed in place by joggles.

joggle joint 1. A joint between two blocks of material (such as masonry) which fit one into the other by a joggle, 1. 2. Same as joggle, 2.

joggled lintel A series of masonry joggle joints, united so as to form a lintel.

joggle piece A joggle post, 2.

joggle post 1. A post made of two or more pieces of timber joggled together. 2. A king post having shoulders or notches at its lower end to support the feet of struts.

joggle tenon Same as stub tenon.

joggle truss A roof truss with a single post placed centrally and fitted to the chord by a sub-tenon or the like, the chord being on top, and the post hanging downward and having its lower end connected with the ends of the chord by oblique braces.

joggle work In masonry, construction in which stones are keyed together by joggles, 1.

joiner’s chisel Same as paring chisel.

joiner’s finish See carpenter’s finish.

joiner’s gauge A marking gauge.

joinery The craft of woodworking by joining pieces of wood, esp. of the finish and trim workings of the interior of a structure, such as doors, paneling, sashes, etc., as distinguished from carpentry, which suggests framing and rough work.

joining The junction of two separate plaster applications of the same coat, usually within a single surface plane.

joint 1. The space between adjacent surfaces (as between masonry units), or the place where two members or components are held together by nails, fasteners, cement, mortar, etc. 2. In steel construction, the area where two or more steel surfaces are attached; often characterized by the type of weld or fastener employed. Also see masonry joint and wood joint.

joint backing Same as backing strip.

joint bolt See handrail bolt.

joint compound In gypsum board construction, a compound used for taping and/or finishing joints.

joint efficiency In welding, the ratio of the strength of a joint to the strength of the base metal; expressed in percent.

jointer 1. A metal tool used to cut a joint partly through fresh concrete. 2. In masonry, a tool for filling the cracks between courses of bricks or stones. 3. In masonry, a bent strip of iron inserted into a wall to strengthen a joint. 4. In carpentry, a long plane, esp. used to square the edges of boards or veneer so that they will make a close joint with other pieces.

jointer plane Same as jointer, 4.

joint factor Same as joint efficiency.

joint fastener See corrugated fastener.

joint filler 1. Any putty-like material used to fill joints, as in plasterboard construction. 2. A strip of extruded resilient material used for filling a joint.

jointing 1. In masonry, the finishing of joints between courses of bricks or stones before the mortar has hardened. 2. The machining of a true and flat surface on one face or edge of a wood member. 3. The first operation in sharpening a cutting tool, whereby the tips of all teeth or knives are ground or filed to the intended cutting circle.

jointing compound Any material used to seal a plumbing joint.

jointing rule A long straightedge used by masons in drawing lines and in pointing.

jointing tool A steel tool used in forming brickwork joints.

jointless flooring Any type of flooring (e.g., terrazzo) that can be laid without construction joints.

joint mold, section mold A shaped template, usually of plywood or zinc; used for casting a plaster member.

joint movement The difference in width of a joint between its fully open and fully closed positions.

joint reinforcement Any type of steel reinforcement, such as reinforcing bars or steel wire, which is placed in or on mortar bed joints.

joint reinforcement tape Any strip of fabric, woven fiberglass, metal, mesh, paper, or other material, used with a cementitious material to reinforce the joint between adjacent gypsum boards.

joint residue An accumulation of foreign matter, old sealant material, and protrusions that must be removed from the walls of a joint prior to sealing.

joint rod, joint rule A piece of metal, usually 2 to 24 in. (approx. 5 to 60 cm) long and 4 in. (10 cm) wide with a 45° angle cut at one end, used to form and shape mitered plaster joints in cornice work.

joint runner In plumbing, an incombustible material (such as asbestos) used to hold molten lead that is poured in the bell of a joint, such as a bell-and-spigot joint.

joint sealant 1. An impervious sealant used to fill joints or cracks in concrete or mortar. 2. See preformed sealant. 3. See jointing compound.

joint shingle A wood roofing shingle that is attached by nailing edge to edge rather than overlapping.

joint tape A tape used to cover joints formed by adjacent sheets of wallboard.

joint tenancy Ownership of property by two or more persons in which, upon the death of one, his interest devolves upon the other or others until a sole owner survives.

joint venture A collaborative undertaking by two or more persons or organizations for a specific project (or projects) having many of the legal characteristics of a partnership.

joist One of a series of parallel beams of timber, reinforced concrete, or steel used to support floor and ceiling loads, and supported in turn by larger beams, girders, or bearing walls; the widest dimension is vertically oriented. Also see binding joist, boarding joist, bridging joist, ceiling joist, common joist, floor joist, principal joist, sleeper joist.

joist anchor A beam anchor.

joist bridging Same as cross bridging.

joist hanger A metal angle or strap used to fix a joist to a beam or girder.

joist trimmer Same as trimming joist.

joule A unit of energy or work; equals the work done by a force of 1 newton which acts over a distance of 1 metre in the direction of the force.

journeyman A person who has successfully served a formal apprenticeship in a building trade or craft and who is thereby qualified to work at that trade in another’s employ. A journeyman’s license (earned through a combination of education, supervised experience, and examination) is required in many locales for those employed at an intermediate level in certain trades, such as plumbing, mechanical work, and electrical work.

jowl The enlarged head or foot of a timber, usually a vertical post; often used to facilitate the joining of other timbers.

JR On drawings, abbr. for “junior.”

JT On drawings, abbr. for “joint.”

jube A screen separating the chancel from the nave or aisles, or both. (See illustration p. 558.)

judas, judas-hole, judas window A small trap or hole in a door for peering or watching, as in a prison door.

judgment lien A charge against property of a judgment debtor (one against whom a judgment has been rendered by a court and who has not paid it) to secure payment of the judgment; may arise automatically in some states by operation of law, and in other states may require certain procedural steps on the part of the judgment creditor; acts as an encumbrance on the property until discharged, usually through satisfaction of the judgment.

Jugendstil “Youth style”; the German version of Art Nouveau.

juliet A medieval stronghold that is circular in plan; a keep.

jumbo A traveling support for concrete forms.

jumbo brick A brick larger in size than standard.

jump A step in a masonry foundation.

jump-cut A tree-pruning technique for removing limbs without stripping bark from the trunk of the tree.

jumper 1. A short length of electric cable fitted with connectors at both ends, connected across a device in an electric circuit so that the current bypasses the device. 2. A steel bar which is moved up and down manually in a borehole in the ground; used as a drilling or boring tool. 3.In a stone wall, a stone that is two or more courses, 1 high.

jumper tube A pipe or hose which is used to bypass the usual flow of a liquid or gas.

jump joint Same as a butt joint or flush joint.

jumpover See return offset.

junction box In electric wiring, a box which protects splices in conductors or joints in runs of raceways or cables; has a removable cover to provide easy access.

junior beam One of the standardized categories of hot-rolled steel, shaped I-beams.

junior channel A lightweight structural channel.

junior college A post-high school institution which offers a 2-year program of study of a terminal nature or in preparation for continued college studies.

junior mortgage One in which the lender’s claim against the owner is subordinate to that of a first mortgage holder or another claim which has priority.

jurisdiction A territory such as a state, province, county, shire, or municipality, that enforces building codes, construction standards, laws, and/or regulations within which its authority is exercised.