| Term | Definition |
| U Bolt | A U-shaped, bent iron bar that has bolts and threads at both ends. |
| U Stirrup | An open-top, U-shaped loop of steel bar used as reinforcing against diagonal tension in a beam. |
| U-Value | See Coefficient of Heat Transmission. |
| UBC | Uniform Building Code. |
| UCC | Uniform Commercial Code. |
| UF Cable | Underground Feeder Cable. |
| UHF Cable | Cable that is designed for ultra-high frequency. |
| UL | Underwriters Laboratories. |
| UL (Underwriters' Laboratories) | An independent testing agency that checks electrical devices and other components for possible safety hazards. |
| ULC | Underwriters Laboratories of Canada. |
| Ultimate Compressive Strength | The stress at which a material crushes. |
| Ultimate Load | The absolute maximum magnitude of load which a structure can sustain, limited only by ultimate failure. |
| Ultimate Strength | Maximum strength that can be developed in a material. |
| Ultimate-Strength Design | Method of structural analysis of continuous concrete structures based on calculating the loadings which will cause actual failure of sections, rather than the loadings which will cause stresses to reach allowable, safe, values. |
| Ultra-Violet Light | Light of short wave length which is invisible but has active chemical effect on finishing materials. |
| Ultramarine | A vivid blue pigment, made from powdered lapiz lazuli. |
| Ultramarine Blue | Blue pigment made by heating a mixture of China clay, sodium carbonate, carbon and sulphur; it is not affected by alkalis, but is easily affected by acids. |
| Ultramicroscopic | Too small to be seen with a normal microscope. |
| Ultrasonic Transmitter | A mechanism that converts vibrations with the same physical nature as sound into equivalent waves above the range of human hearing. |
| Ultraviolet | 1. The invisible rays of the spectrum at the violet end. 2. Invisible radiation waves with frequencies shorter than wave lengths of visible light and longer than X-ray. |
| Umber | A natural earth pigment like ochre but darker and browner. |
| Unadulterated | Not contaminated; pure. |
| Unbalanced Wall | See Unsymmetrical. |
| Unbalancing the Schedule of Values | See Front end loading. |
| Unbonded Construction | 1. Post-tensioned concrete construction in which the tendons are not grouted to the surrounding concrete. 2. A construction contract in which the contractor has not posted a surety bond. |
| Unbuffed End | An untrimmed, serrated factory cut end. |
| Uncertainty | The doctrine that contracts are unenforceable if unintelligible |
| Unconscionability | A doctrine that courts will not enforce contractual provisions that put one party at the mercy of another. |
| Unctuous | Oily; of minerals, having a greasy or soapy feel. |
| Uncut loop | Carpet pile yarns that are continuous from tuft to tuft, forming visible loops. |
| Underatomized | Not dispersed or broken up fine enough. |
| Underbead Crack | In welding, a crack in the heat-affected zone not extending to the surface of the base metal. |
| Underbid | To bid less than a competing bidder. |
| Undercapitalized | Having too little capital for efficient operation. |
| Undercoat | A coating applied prior to the finishing or top coats of a paint job. It may be the first of two or the second of three coats. Sometimes called the Prime coat. |
| Undercourse | A course of shingles laid beneath an exposed course of shingles at the lower edge of a wall or roof, in order to provide a waterproof layer behind the joints in the exposed course. |
| undercurtains | Curtains that hang behind the main curtains or draperies. |
| Undercut | A groove at the base metal adjacent to the toe of a weld and left unfilled by weld metal. |
| Underdrain | 1. Perforated pipe drain installed in crushed stone under a slab to intercept ground water and drain it away from the structure. 2. The distribution system at the bottom of a sand filter to collect the filtered water during a filter run and to distribute |
| Underestimate | An estimate that is too low. |
| Underfloor Duct | A round or rectangular metal pipe placed under a wood floor construction or in a concrete floor to distribute warm air from a heating or air conditioning system. |
| Underglaze Decoration | A ceramic decoration applied directly on the surface of ceramic ware and subsequently covered with a transparent glaze. |
| Underground | Subterranean. |
| Underground Feeder Cable | Insulated electrical cable suitable for underground use. |
| Underground Paper | Wallpaper without a basic background color. |
| Underground plumbing | The plumbing drain and waste lines that are installed beneath a basement floor. |
| Underground Tank | A container that holds various liquid or solid matter and is found underground. |
| Underground Tank Removal | The excavation and removal process of a storage tank buried in the ground. |
| Underlay | 1. One or more layers of felt applied as required for a base sheet over which finish roofing is applied. 2. See Carpet Padding. |
| Underlayment | A ΒΌ" material placed over the subfloor plywood sheeting and under finish coverings, such as vinyl flooring, to provide a smooth, even surface. Also a secondary roofing layer that is waterproof or water-resistant, installed on the roof deck and beneath shi |
| Underpinning | The process of placing new foundations beneath an existing structure. |
| Underslab Drainage | The process of continuous interception and removal of ground water from under a concrete slab with the installation of perforated pipe. |
| Undertone | A color covered up by other colors but when viewed by transmitted light, shows through the other colors modifying the effect. |
| Underwater Light | A lighting fixture designed to illuminate a pool from beneath the water surface; it can be wet-niche, located in the pool water, or dry-niche, located in the pool wall and serviced from outside the pool. |
| Underwriters Laboratories (UL) | An organization which classifies roof assemblies for their fire characteristics and wind-uplift resistance for insurance companies in the United States. |
| Underwriters Laboratories of Canada (ULC) | 7 Crouse Road, Scarborough, Ontario, Canada M1R 3A9, (416) 757-3611. |
| Underwriters Laboratories, Inc (UL) | 333 Pfingsten Road, Northbrook, Illinois 60062, (708) 272-8800. |
| Undivided Interest | Joint ownership of an interest in the whole property rather than in a specific identifiable part |
| Unemployment Tax | A program funded by employers based on the wages of employees, paid on a quarterly basis to the Unemployment Insurance Fund from which benefits are paid to qualifying ex-employees. |
| Unencumbered Property | Real property that has no liens, encumbrances, easements, or debt; free and clear. |
| Unequal Angle | A steel angle in which the two legs are of different lengths. |
| Unfaced Insulation | Insulation which has been manufactured without a vapor barrier. |
| Unfinished Bolt | An ordinary carbon steel bolt. |
| Unforeseen Conditions | Unexpected or unanticipated events or situations on the jobsite or locality above or below grade that affect the contract price or time. |
| Unglazed Floor | A hard ceramic floor surface deriving its color or texture from the materials used with uniform composition throughout. |
| Unglazed Floor Tile | A hard, dense floor tile deriving color and texture from the materials used and the method of manufacture, with uniform composition throughout. |
| Unglazed Tile | A hard, dense tile of homogeneous composition throughout, deriving color and texture from the materials of which the body is made; the colors and characteristics of the tile are determined by the materials used in the body, the method of manufacture, and |
| Ungrounded Cable | Two-wire nonmetallic sheathed cable that contains one neutral wire and one hot wire. |
| Uniform Building Code (UBC) | A model building code written by the International Building Officials Conference and adopted by many cities and counties as their official building code. |
| Uniform Commercial Code (UCC) | A statute governing commercial transactions, sales, and commercial paper that has been adopted in substantially the same form in all 50 states. |
| Uniform Sand | A mixture of sand in which most of the granules are the same size. |
| Union | A plumbing fitting that joins pipes end-to-end so they can be dismantled. |
| Union | A type of pipe fitting used to join two pipes in line without turning either pipe. |
| Union Hub | A pipe fitting used to join two pipes without turning either pipe, with one end of the fitting enlarged into a bell or socket. |
| Union T | A pipe tee with a fitting on one end that joins two pipes without turning either pipe. |
| Union, Brass | A pipe fitting constructed of brass, used to join two pipes without turning either pipe. |
| Union, PVC | A pipe fitting used to join two pipes without turning either pipe, manufactured from polyvinyl chloride and used mainly in drain lines because of its resistance to chemicals. |
| Union, Stainless | A pipe fitting used to join two pipes without turning either pipe, manufactured from stainless steel. |
| Unit and Mullion System | A curtain wall system consisting of prefabricated panel units secured with site-applied mullions. |
| Unit Cost | 1. Cost per unit. 2. Cost per unit of length, volume or area. |
| Unit Heater | A device for heating a space without the use of ductwork. |
| Unit Masonry | Manufactured or natural building units of concrete, burned clay, glass, stone, gypsum, etc. |
| Unit of Work | Calorie, erg, foot-pound, joule, poundal; unit of electrical power, amp, amperage, ampere, kilowatt, megawatt, ohm, voltage, volt, wattage, watt. |
| Unit Price | 1. The price charged for a single unit or minimum unit of production. 2. The price charged for a unit of length, volume, or area. |
| Unit Stress | The force on a member divided by its cross-sectional area, such as pounds per square inch. |
| Unit Substation | A freestanding assembly including a transformer, switchgear and meter. |
| Unit Vent | A vent pipe which services two or more traps. |
| Unit Ventilator | A fan coil unit with an opening through an exterior wall to admit outside air. |
| Unit Water Content | The quantity of water per unit volume of freshly mixed concrete, often expressed as gallons or pounds per cubic yard; this is the quantity of water on which the water- cement ratio is based and does not include water absorbed by the aggregate. |
| Unit Weight | The weight of a unit volume of a substance; its density. |
| Unitary Package Unit | A system of conditioning air in an outdoor package unit, similar to a rooftop unit, except that the supply and return ductwork passes horizontally through an outside wall. |
| Unitary System | A heating/cooling system factory assembled in one package and usually designed for conditioning one space or room. |
| United States Customary Systems | The measuring units used in the U.S. consisting of the mile, foot, inch, gallon, second, and pound; also called Imperial Units; these units are gradually being replaced by SI units. |
| United States Standard | Sheet metal gauge. |
| Universal | Description of a lock, door closer, or other device that can be used on doors of any hand without change. |
| Universal Motor | Electric motor which will operate on either a-c or d-c. |
| Unjust Enrichment | A situation in which one party is unjustly enriched at the expense of another party. |
| Unlawful Detainer Action | A lawsuit brought to evict a defaulting tenant from real property. |
| Unlined Stack | A chimney built of brick only, possibly lined with a coat of cement plaster, but with no terra cotta flue lining. |
| Unplasticized Polyvinyl Chloride | (uPVC).A stiff plastic material of which doors, windows, corrugated roofing and other building components are made. |
| Unrated Door | A door which has not been rated for any ability to withstand the spread of fire. |
| Unravel | To lose material from the edges of a revetment. |
| Unreasonable Hardship | This exists when the enforcing agency finds that compliance with the building standard would make the specific work of the project affected by the building standard unfeasible, based on an overall evaluation of all relevant factors, including cost, value, |
| Unreinforced | Concrete members constructed without steel reinforcing bars or welded wire fabric. |
| Unsaponifiable Water | Substance in resins and fats which does not unite with caustic alkali to form a soap. |
| Unstable | A structure that lacks stability. |
| Unsymmetrical Wall | An assembly of multiple layers of gypsumboard where one side has more layers or a different construction than the other; also called an Unbalanced Wall. |
| Untreated Joint | A gypsumboard joint without joint compound, tape, or battens. |
| Updrift | The direction opposite that of the predominant movement of littoral materials. |
| Uplift | An upward force. |
| Upper bank | That portion of the streambank above the elevation of the average water level of the stream. |
| Upset Price | A guaranteed maximum price in a construction contract. |
| Upside Down Roof | A membrane roof assembly in which the thermal insulation lies above the membrane. |
| uPVC | Unplasticized Polyvinyl Chloride. |
| Urban Renewal | The redevelopment of a deteriorated inner city area. |
| Urea | A crystalline colorless nitrogenous compound found primarily in the urine of mammalian animals; can be synthesized from carbon dioxide and ammonia for use in fertilizers, resins, and plastics. |
| Urea-Formaldehyde Foam | An aerated foam of a thermosetting synthetic resin composed of urea and formaldehyde; used for thermal insulation. |
| Urea-Formaldehyde Resin | Product obtained by chemical reaction between urea and formaldehyde in presence of catalyst. |
| Urea-Melamine Resin | Melamine-formaldehyde resins which produce tough finish that approaches porcelain. |
| Urethane Board | Rigid form of plastic foam of polyurethane. |
| Urethane Foam | Type of insulation which is foamed in between inner and outer walls of a container. |
| Urethane Insulation | Board form or sprayed on plastic foam of rigid polyurethane. |
| Urethane Padding | Plastic foam of polyurethane used under carpeting for cushioning. |
| Urethane Resins | A particular group of film formers; Isocyanate resins. |
| Urethane Roof | A roof with plastic foam of rigid polyurethane; made into board form or sprayed on. |
| Urethane, Rigid | Sheet or board form of plastic foam of rigid polyurethane. |
| Urinal | A water flushed plumbing fixture designed to receive urine directly from the user of the fixture. |
| Urinal Carrier | A metal structure attached to a bathroom wall to support and mount a urinal. |
| Urinal Screen | A privacy panel that separates urinals from each other; the screens are either floor, wall or ceiling mounted. |
| Urn, Coffee | See Coffee Urn. |
| US Department of Justice (DOJ) | 10th & Constitution Avenue, NW, Washington, DC 20530, (202) 514-2000. |
| USC | United States Code. |
| USC&GS | United States Coast and Geodetic Survey. |
| USCS | United States Customary Systems. |
| USDA | United States Department of Agriculture. |
| Useful Life | The length of time a coating is expected to remain in service. |
| USGS | United States Geological Survey. |
| USP | Letters affixed to name of material to indicate that it conforms in grade to specifications of United States Pharmacopoeia and that it is approved for use in medicinal preparations. The material does not necessarily have to be chemically pure. |
| USS | United States Standard. |
| Usury | Charging more than the maximum legally allowable rate of interest. |
| Utensil Washer, Medical | See Medical Utensil Washer. |
| Utility | A service provided by a public utility, such as electrical power or water. |
| Utility easement | The area of the earth that has electric, gas, or telephone lines. These areas may be owned by the homeowner, but the utility company has the legal right to enter the area as necessary to repair or service the lines. |
| Utility Excavation | The act or process of either digging up existing cable buried in the ground, or trenching to lay new cable. |
| Utility Knife | 1. A commonly used razor-type blade and holder. 2. See Board Knife. |
| Utility Pole | A vertical pole with cross arms, where electrical and telephone lines are carried. |
| Utility Room | A room housing domestic appliances such as a laundry. |
| Utilization Equipment | Equipment which utilizes electric energy for mechanical, chemical, heating, lighting, or similar useful purposes. |
| UV | Ultraviolet. |