U

UL Certified A certificate, issued to a manufacturer for one of its products, which indicates that the product has been tested in the US by the Underwriters Laboratories, Inc. (UL) and has met UL requirements.

UL Label An identification affixed to a building material or component, with the authorization of Underwriters’ Laboratories, Inc., indicating that the labeled product: (a) has a rating based on the performance tests of such products; (b) is from a production lot found by examination to be made from materials and by processes essentially identical to those of representative products which have been subjected to appropriate fire, electrical hazard, or other tests for safety; and (c) is subject to the reexamination service of UL.

UL Listed See UL Label.

ultimate bearing capacity The average load per unit of area required to produce failure by rupture of a supporting soil mass.

ultimate bearing pressure The pressure at which a foundation sinks without a further increase in load.

ultimate load See breaking load.

ultimate set The final degree of firmness attained by a plastic compound after curing, evaporation of volatile materials, and surface polymerization.

ultimate shear strength The loading at a section resulting from the failure of a member in shear.

ultimate shear stress The stress at a section which is loaded to its maximum in shear.

ultimate strain The strain at which a material fails under test.

ultimate strength Of a material in tension, compression, or shear: the maximum value of tension, compression, or shear, respectively, that the material can sustain without failure.

ultimate stress The stress at which a material fails under test.

ultramarine A blue pigment used in paint; once obtained from crushed lapis lazuli; now manufactured synthetically by calcining aluminum silicate and sodium sulfide; has good alkali resistance, but is sensitive to acids.

ultramarine ash The residue of lapis lazuli after the ultramarine has been extracted; used as a pigment in paints.

ultrasonic motion detector A motion detector employing sound waves having a frequency usually above 20,000 Hz.

ultrasonic soldering A soldering process in which high-frequency sound waves are transmitted through molten solder to remove undesirable surface films from the base metal, thereby promoting wetting of the base metal with solder; usually accomplished without the use of flux.

ultrasonic testing A nondestructive method of testing metal; makes use of very-high-frequency sound waves to locate flaws in metal.

ultrasonic welding A solid-state welding process in which the metals are joined by the local application of high-frequency sound waves as the work parts are held together under pressure.

ultrasound Acoustic oscillations having a frequency above the high-frequency limit of audible sound, i.e., above 20,000 Hz.

ultraviolet radiation Electromagnetic radiation at wavelengths immediately below the visible spectrum, i.e., within the wavelength range 10 to 380 nm. May be classified as: far ultraviolet, 10 to 280 nm; middle ultraviolet, 280 to 315 nm; near ultraviolet, 315 to 380 nm. Also may be classified as: ozone-producing, 180 to 220 nm; germicidal, 220 to 300 nm; erythemal, 280 to 320 nm; black light, 320 to 400 nm. In either method of classification, there are no sharp demarcations between the wavelength bands.

umber A naturally occurring brown siliceous earth, containing hydrated iron oxide with small amounts of manganese oxide; used as a pigment in paint; turns red to reddish-brown when calcined, and then is called burnt umber.

umbrage 1. An open area recessed in the main body of a building; protected by the ceiling and floor above. 2. A sheltered, shady space in the open air, usually relatively small.

umbral In Spanish Colonial architecture, a lintel.

umbrella roof In French Vernacular architecture of Louisiana, a roof having a single pitch on each side of a central ridge and covering a galerie on each side of the house.

umbrella vault A vault that has ribs which fan out from a central support.

unbonded member A posttensioned, prestressed concrete member in which tensioning force is applied against end anchorages only, the tendons being free to move within the element.

unbonded posttensioning In prestressed concrete, posttensioning in which the tendons are not grouted to the concrete after being stressed.

unbonded tendon In prestressed concrete, a tendon which is not bonded to the concrete.

unbraced frame A structural framework in which the resistance to lateral load, 1 is provided by the bending resistance of its structural members and their connections.

unbraced length The distance between ends of a structural member (such as a column) which are prevented from moving normal to the axis of the member, by bracing, by floor slabs, etc.

unburnt brick Brick, such as adobe brick, that is sun-dried, rather than kiln-dried at an elevated temperature; compare with burnt brick.

uncased Said of an arch, doorway, or other opening that has no frame around it. Uncased openings are especially found in Spanish Eclectic architecture and its derivatives.

unclassified excavation An excavation in which there is a single unit price for removal, regardless of the proportion of common excavation and rock excavation (compare with classified excavation).

unconsolidated backfill The non-compacted material which is in place in a trench.

uncoursed Said of masonry which is not in layers with continuous horizontal joints, but is laid irregularly.

unctuarium Same as alipterion.

uncut modillion See modillion.

undé, undée See waved molding.

underbed The base mortar, usually horizontal, on which a terrazzo topping is applied.

underboarding Boards that are nailed to the exterior side of the framing of a timber-framed house to provide a surface on which to fasten an exterior covering such as shingles or siding.

undercloak 1. In roofing, a course of plain tiles or slate used under the first course at the eaves. 2. Shingles installed with their thick end overhanging the edge of a gable to give a slope to the tiles laid along the edge. 3. In sheet-metal roofing, that part of the lower sheet that makes up a seam, or the like.

undercoat 1. A coat of paint applied on new wood, or over a primer, or over a previous coat of paint; improves the seal and serves as a base for the topcoat, for which it provides better adhesion. 2. Any paint which acts as a base for enamel. 3. Any primer which is colored.

underconsolidated soil deposit A deposit that is not fully consolidated under the existing overburden pressure.

undercourse A course of shingles or tiles which serves as an undercloak, 1, 2.

undercroft 1. A vaulted basement of a church or secret passage, often wholly or partly below ground level. 2. A crypt.

undercured Said of concrete, a sealant, adhesive, paint, etc., which has not had sufficient time and/or suitable physical environment to harden properly.

undercut 1. In stonework, to cut away a lower part, leaving a projection above that serves the function of a drip. 2. To rout a groove or channel (a drip) back from the edge of an overhanging member.

undercut door A door without louvers which is given additional clearance at the floor line to provide ventilation.

undercut tenon A tenon in which a shoulder is cut at an angle to the face of the tenon in order to ensure a tight fit.

underdrain A drain, installed in porous fill, for drawing off surface water or water from the soil, as under the slab of a structure.

underdrawing Same as torching.

under-eaves course A short course of roof tiles laid beneath the first course of tiles at the eaves of the roof.

underfelt 1. A dry sheet of asphaltic felt. See underlayment, 2. 2. A padding material comprised of hair felt, or some combination of felt and jute, laid directly on the floor, over which carpet is installed; a type of underlayment.

underfill A depression, on the face of a weld, which extends below the surface of the adjacent base metal.

underfloor Same as subfloor.

underfloor conduit system A method of distributing communications wiring within the floor of a building. Metal pipes (for housing the wiring) radiate out to the area served from a serving closet (or cabinet). Such a system is suitable for installation in buildings in which the terminal equipment locations are likely to remain fixed.

underfloor heating Heating provided beneath a finish floor, usually by hot water pipes or electric heating cables. See radiant heating system.

underfloor raceway A raceway, for carrying electric conductors, which is suitable for use in a floor, as one buried within a structural concrete floor.

undergird To secure, support, or strengthen a structure by tying together a number of individual elements below the soffit of the structure above it.

underglaze decoration A ceramic decoration applied directly on the (bisque) surface of ceramic ware and subsequently covered with a transparent glaze.

underground Below grade or ground level, as underground drain lines or cables.

underground construction See earth-sheltered construction.

underground distribution system An electrical supply system employing underground structures, cables, and other equipment located under designated areas along public ways or utility easements; does not include service cables in the customer’s duct.

underground piping Piping in direct contact with, and covered by, earth.

underground service Said of an element of building service, such as an electrical cable or a pipe, that is buried in the ground.

underground structure Any duct, manhole, subway-type pull box, underground-type enclosure, or vault in which cables, transformers, and similar items of equipment are installed.

underlay 1. Same as underlayment. 2. Same as carpet underlayment. 3. A layer, such as asphaltic felt, which isolates a roof covering from the substructure; underfelt.

underlayment 1. A material such as plywood or hardboard placed on a subfloor to provide a smooth, even surface for applying the finish. 2. The material, usually No. 15 felt, used to cover a roof deck before shingles are applied; also called underfelt. 3. See carpet underlayment.

underlining felt Same as underlayment, 2.

underpinning The rebuilding or deepening of the foundation of an existing building to provide additional or improved support, e.g., additional support required as a result of a new excavation in adjoining property which is deeper than the existing foundation.

underpitch groin A groin formed by an underpitch vault.

underpitch vault, Welsh vault A construction formed by the penetration of two vaults of unequal size, springing from the same level.

under plate See armored front.

undersanded concrete Concrete containing an insufficient proportion of fine aggregate to produce optimum properties in the fresh mixture, esp. with respect to workability and finishing characteristics.

undersealing Same as subsealing.

underslating felt Same as underlayment, 2.

underslung car frame An elevator car frame having the fastenings or sheaves for the hoisting ropes (cables) attached at or below the car platform.

underthroating The cove of an outside cornice when treated so as to serve as a drip.

undertone 1. A color modified by an underlying color, as in the effect of glazing over a thin film of paint. 2. A secondary color of a pigment which appears when it is diluted with a large amount of white.

Underwriters’ Laboratories, Inc. A nonprofit nongovernment organization sponsored by the National Board of Fire Underwriters; classifies, tests, and inspects electric devices to assure their compliance with the National Electrical Code.

Underwriters’ loop See Hartford loop.

undisturbed sample A sample of soil that has been obtained by methods in which every precaution has been taken to minimize disturbance to the sample.

undressed lumber, rough lumber, Brit. unwrought timber Sawn lumber that has not been planed.

undue burden A legal term used to indicate that in the particular case under consideration, it would be a significantly difficult and/or expensive burden to meet all aspects of the Americans with Disabilities Act.

undulating molding See wave molding.

undulating tracery See flowing tracery.

undy molding See wave molding.

uneven grain Wood grain in which the growth rings show an obvious difference between spring-wood and summerwood; found in ring-porous hardwoods (such as oak) and softwoods (such as yellow pine) that have soft, uniform springwood and hard, dense summerwood.

unfinished bolt A bolt fabricated of low-carbon steel.

unfired brick A solid masonry unit that has not been fired in a kiln at a high temperature.

unframed door A door not in a frame, as a batten door.

ungauged lime plaster Plaster containing no gypsum; usually composed of lime, sand, and water.

unglazed tile A hard, dense ceramic tile for floors or walls; of homogeneous composition throughout, deriving its color and texture from the materials of which the body is made and from the method of manufacture.

unidirectional microphone A microphone whose response is predominantly from a single direction.

Uniform Building Code (UBC) 1. A US national building code, prepared and issued by the International Conference of Building Code Officials, 5360 South Workman Mill Road, Whittier, CA 90601-2294. Also see BOCA National Building Code. 2. Any model code, similar to 1, of a country other than the US.

uniform construction index An outline of building trades and products, separated into 16 divisions (illustrated under contract documents), that are arranged by trade and construction sequence.

Uniform Federal Accessibility Standards (UFAS) A set of standards concerning accessibility for the disabled, which are available at no charge from: US Access Board, 1331 F Street NW, Suite 1000, Washington, DC 20004-1111. Also see Americans with Disabilities Act.

uniform grading A particle-size distribution of aggregate in which all pan fractions are present without a preponderance of any one size or group of sizes.

uniformity coefficient A coefficient related to the size distribution of a granular material, such as sand; obtained by dividing one size of grain (60% of the grains are smaller than this size, by weight) by a second size (10% of the grains are smaller than this size, by weight).

uniform load A load, 1 uniformly distributed over all or a portion of a structure.

uniform settlement The sinking into the ground of various parts of a building at the same rate.

uniform system Coordination of specification sections, filing of technical data and product literature, and construction cost accounting, organized in 16 divisions based on an interrelationship of place, trade, function, or material.

uninterruptible power system An electric power system which provides continuity of power, to the apparatus or appliances being served, without discernible interruption upon failure of the normal power supply.

union A pipe fitting, 1 used to connect the ends of two pipes, neither of which can be turned; consists of three pieces, the two end pieces (having inner threads), which are tightened around the pipe ends to be joined, and a center piece, which draws the two end pieces together as it is rotated, effecting a seal. Also see flange union.

union bend See union elbow.

union clip A fitting for interconnecting the ends of two rainwater gutters.

union elbow A pipe elbow, 1 having a union-type coupling on one end, so that the coupling end may be connected to the end of a pipe without turning the pipe.

union fitting A union elbow or a union tee.

union joint A pipe joint made with a union.

union tee A pipe tee having a union-type coupling on one end.

union vent Same as dual vent.

unit absorber A sound-absorptive element which is designed for application on a wall or ceiling as a single unit; usually part of a spaced array of similar units.

unit air conditioner Same as room air conditioner.

unitary air conditioner Equipment consisting of one or more factory-fabricated assemblies designed to perform the functions of air moving, air cleaning, cooling, and dehumidification; the assemblies usually include a fan, evaporator or cooling coil, and a compressor and condenser in combination; a heating unit also may be included.

unit construction Same as modular construction.

unit cooler See room air conditioner.

united inches The sum of the length and width (expressed in inches) of a rectangular piece of glass.

United States of America Standards Institute See American National Standards Institute.

unit heater A direct-heating, factory-made, encased assembly including a heating element, fan and motor, and directional outlet.

unit lock A preassembled lock.

unit masonry See masonry unit.

unit price An amount stated in a contract as the price per unit of measurement for materials or services as described in the contract documents.

unit stress The value obtained by dividing the total stress by the cross-sectional area that is stressed.

unit substation One or more transformers which are mechanically or electrically connected to (and coordinated in design with) one or more switchgear or motor control assemblies, or combinations thereof.

unit system A curtain wall, 1 composed entirely of prefabricated units attached to the building structure.

unit-type vent An opening of relatively small area (one of a number which are distributed about a roof according to the occupancy requirements), usually having a lightweight metal frame and housing, with hinged dampers which may be operated manually or which open automatically in the event of fire.

unit vent See dual vent.

unit ventilator An operable air-inlet damper which furnishes outdoor air to an interior space; may be provided with a filter and heating and/or cooling coils.

unit water content 1. The quantity of water per unit volume of freshly mixed concrete. 2. The quantity of water on which the water-cement ratio is based, not including water absorbed by the aggregate.

universal Descriptive of a door lock, a door closer, or the like, which can be used on either a right-hand swing door or a left-hand swing door.

universal motor A motor capable of operating either on alternating current or on direct current.

unloader A control mechanism for an electric-motor-driven compressor; controls the pressure head of the compressor; permits the motor to be started at low starting torque by removing the load during this initial period of operation.

unprotected corner Of a slab, a corner having no adequate provisions for transfer of load, so that the corner must carry over 80% of the load.

unprotected metal construction Steel frame construction in which the framing members are not fireproofed.

unreinforced concrete See plain concrete.

unrestrained member A member that is permitted to rotate freely at its points of support.

unseasoned lumber Same as green lumber.

unsound Descriptive of a plaster, slaked lime, cement, or other mortar which contains particles that may expand.

unsound knot, decayed knot, rotten knot A knot that is softer than the surrounding wood.

unsound plaster Hydrated lime, plaster, or mortar which contains unhydrated particles that may expand and cause popping or pitting.

unsound wood Same as decayed wood.

unstable equilibrium The condition of a structure in a state of equilibrium; when a slight disturbance is applied to the structure and then removed, the structure does not return to its original equilibrium position. Compare with stable equilibrium.

unstable soil Earth material that, because of its nature or the influence of related conditions, cannot be depended upon to remain in place without extra support, such as would be furnished by a system of shoring.

unstiffened member A member (or part of a member) which is subjected to compressive forces and is not reinforced in a direction perpendicular to the direction along which it will bend most easily.

unsupported length The distance between the end supports of a beam.

unwrought timber, unwrot timber British term for undressed lumber.

up-and-down sash An archaic term for a rectangular window sash that moves in a vertical plane; a double-hung window.

up-and-over door An overhead door which is a single leaf.

UPC Abbr. for “Uniform Plumbing Code.”

upfeed system A water distribution system in which water is supplied and fed upward through the vertical piping to the highest point of the system that may be fed, using the available pressure.

upheaval The upward push of a soil mass.

U-plan The basic plan of a house having a shape similar to that of the capital letter U.

uplift 1. The upward pressure on a structure due to the pressure of the water below. 2. The pressure acting on a material that tends to lift it off its supports or fasteners as a result of an external force (for example, wind) acting on it.

uplift capacity A measure of the resistance of a pile to being pulled out of the ground.

upper capital Same as dosseret.

upping block Same as horse block.

upright 1. A vertical piece of timber or stone. 2. A vertical structural member.

upset 1. To shorten and thicken by hammering, as a bar of heated metal struck on the end. 2. In the region of a weld, a localized increase in volume resulting from the application of pressure. 3. A defect in timber due to a severe blow that breaks the fibers across the grain.

upset price See guaranteed maximum cost.

upsetting The hot-forging operation by which the cross-sectional area of a metal bar or rod is increased locally.

upset welding A resistance-welding process in which the joining of two surfaces is effected by the heat obtained from the flow of current through the resistance provided by the area of contact between the surfaces to be joined; pressure is employed in this process.

upside-down roof Same as inverted roof.

upstage The back part of a stage, away from the audience.

up stairs Stairs designated to be used for going up only, as in some schools and institutional buildings.

upstairs The portion of a house or small building situated on the floors above the main or entrance floor.

upstand, upturn The part of a roof covering that turns up against a vertical surface.

upstanding beam In a concrete floor, a beam which projects above a concrete slab rather than below it.

upzoning A change in the zoning classification of a property from one of lower use to one that is of higher use; for example, a change from residential to commercial use.

UR On drawings, abbr. for urinal.

urban area An area which is within the city limits, or closely linked to it by common use of public utilities or services.

urban planning See city planning and community planning.

urban renewal The improvement of slum, deteriorated, and underutilized areas of a city; generally implies improvement realized through city, state, and, particularly, federal programs, including the clearance and redevelopment of slums, the rehabilitation of relatively sound structures, and conservation measures to arrest the spread of deterioration.

urban sprawl An unplanned development of open land, usually on the outskirts of a city.

urea-formaldehyde Same as urea resin adhesive.

urea resin adhesive A dry powder which is mixed with water before being applied; has high early strength and good resistance to heat; not recommended for poorly fitted joints or outdoor use.

urilla Same as volute, 1.

urinal A sanitary fixture equipped with a water supply and drain for flushing away urine.

usable floor area The net floor area in a building after deducting the area occupied by lobbies, corridors, rest rooms, cafeterias, etc.

usable life See pot life.

USASI Abbr. for American National Standards Institute.

US Customary Units The system of units ordinarily used in the US, for example, the unit of length may be the inch, foot, yard, or mile.

use district An area, designated in the zoning ordinance of a municipality, within which specified types of land use are permitted and others forbidden.

USG On drawings, abbr. for “United States gauge.”

U-stirrup In reinforced concrete construction, a stirrup, 2 which is U-shaped.

U-tie A U-shaped heavy wire used as a wall tie.

utility See public utility.

utility pole An outdoor pole installed by a telephone or electric utility company for the support of conductors and other electric or telephone equipment.

utility sheet Mill-finished metal sheeting; available in a variety of sizes suitable for general building construction.

utility tractor A low- to medium-horsepower tractor; used primarily for pulling auxiliary equipment, but also used in construction with attachments for trenching, dozing, breaking, etc.

utility vent A vent, 1 which rises well above the highest water level of a fixture and then turns downward before it connects to the main vent or stack vent.

utility window A low-cost hot-rolled steel window for use in basement areaways, garages, shops, and the like; usually has a hopper light over a fixed light.

utilization equipment Any equipment which utilizes electric energy for mechanical, heating, lighting, or similar useful purposes.

utilization factor 1. The maximum demand of a system (or part of a system) divided by its rated capacity. 2. See coefficient of utilization.