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Term Definition
Thermal Radiation

The transmission of heat from a hot surface to a cool one by means of electromagnetic waves.

Thermal Resistance (R)

Resistance of a material or assembly to the flow of heat. It is the reciprocal of the heat transfer coefficient: (1/C, or 1/U)

For insulating purposes, low "C" and "U" values and high "R" values are the most desirable.

Thermoforming

A process in which heated plastic sheets are made to assume the contour of a mold by using the force of air pressure, vacuum, or mechanical stretching.

Thermoplastics

Plastics that soften by heating and reharden when cooled without changing the chemical composition.

Thermosetting Plastics

Cured plastics that are chemically cross-linked and when heated will not soften but will be degraded.

Thermostat

A temperature-sensitive instrument that controls the flow of electricity to units used to heat and cools spaces in a building.

Threshold

Raised member at the floor within the door jamb. Its purpose is to provide a divider between dissimilar flooring materials or serve as a thermal, sound or water barrier.

Through-penetration Fire Stop

A system for sealing through-penetrations in fire-resistant floors, walls and ceilings.

Through-penetrations

Through-penetration, or "poke-through" openings as they are sometimes called, are holes that penetrate an entire floor or wall assembly to allow the passage of piping, ducts, conduit, cable trays, electrical cables, communications wiring, etc.

Throw

The horizontal or vertical distance an airstream travels after leaving the air outlet before it loses velocity.

Tieback Anchors

Steel anchors grouted into holes drilled in the excavation wall to hold the sheeting, thus reducing the number of braces required.

Timber

Wood structural members having a minimum m thickness of 6 inches (140 mm).

Timber Joinery

The joining of structural wood members using wood joints, such as the mortise and tenon.

Time-Temperature Curve

Rate of rise of temperature in a fire-testing furnace.

Toenail

Method of fastening two boards together as in a "T" by driving nails into the board that forms the stem of the "T" at an angle so they enter the other board and cross each other.

Tolerance

The permissible deviation from a given dimension or the acceptable variation in size from the given dimension.

Tongue-and-Groove Joint

Joint where the projection or "tongue" of one member engages the mating groove of the adjacent member to minimize relative deflection and air infiltration; widely used in sheathing, flooring and paneling. Tongues may be in "V," round or square shapes.

Topcoat

The final coat of paint.

Torque

A twisting or rotating action.

Torsion Strength

The maximum stress a material will withstand before fracturing under a twisting force.

Torsion Test

A test used to ascertain the behavior of materials subject to torsion.

Toughness

A measure of the ability of a material to absorb energy from a blow or shock without fracturing.

Transformer

An electrical device used to convert an incoming electric current from one voltage to another voltage.

Transmission Loss (TL)

Essentially the amount, in decibels, by which sound power is attenuated by passing from one side of a structure to the other. TL is independent of the rooms on each side of the structure and theoretically independent of the area and edge conditions of the structure.

Trap

A device used to maintain a water seal against sewer gases that back up the waste pipe. Usually, each fixture has a trap.

Tread

Horizontal plane or surface of a stair step.

Trimmer

Double joists or rafters framing the opening of a stairway well, dormer opening, etc.

Troweling

Producing a final smooth finish on freshly poured concrete with a steel-bladed tool after the concrete has been floated.

Truss

Open, lightweight framework of members, usually designed to replace a large beam where spans are great.

Truss Plate

A steel plate used to strengthen the joints in truss assemblies.

Truss-Framed System

An assembled truss uint made up of a floor truss, wall stud, and a roof truss.

Tufted Construction

Carpet formed by stitching the pile yarn through the backing material.

Twist

Warping in which one or more corners of a piece o wood twist out of the plane of the piece.

Two-Way Concrete Joist System

Floor and roof construction that has two perpendicular systems of parallel intersecting joists.

Two-Way Flat Plate

Reinforced concrete construction in which the main reinforcement runs in two directions and both surfaces are flat planes and it is supported by columns.

Two-Way Flat Slab

Reinforced concrete floor or roof construction in which a two-way flat plate is supported by columns with drop panels or column capitals.

U of C

University of California, an independent fire-testing laboratory.

U Value

Coefficient of heat transfer, "U" equals 1 divided by (hence, the reciprocal of) the total of the resistances of the various materials, air spaces and surface air films in an assembly. See Thermal Resistance.

UBC

Uniform Building Code - document promulgated by the International Conference of Building Officials.

UL

Underwriters Laboratories Inc., founded by NBFU, and now operated in affiliation with American Insurance Assn. UL is a not for profit laboratory operated for the purpose of testing devices, systems and materials as to their relation to life, fire and casualty hazard in the interest of public safety.

Ultimate Strength

The maximum stress, such as tensile, compressive, or shear, that a material can withstand.

Ultimate Tensile Strength

The maximum tensile stress of a  material up to the point of rupture.

Ultrasonic Testing

A method of non-destructive testing of materials that uses high frequency sound vibrations to find defects in the material.

Under-Carpet Wiring

A flat, insulated electric wire that is run under the carpet.

Underlayment

Sheet material, such as hardboard, that is laid over the subfloor to provide a smooth, stiff surface for the finish flooring.

Underpinning

Placing a new foundation below the existing foundation.

Unfibered Gypsum

A neat gypsum. It has no additives.

Uniform Load

Any load that is spread out evenly over a large area.

Unreinforced Concrete

Concrete placed without steel-reinforcing bars or welded-wire fabric.

USASI

United States of America Standards Institute, now American National Standards Institute.

Valence

The points on an atom to which valences of other elements can bond.

Valley

The intersection of two inclined surfaces.

Vapor Retarder

Material used to slow the flow of water vapor through walls and other spaces where this vapor may condense at a lower temperature.

Varnish

A thin sheet of material used to cover another surface.

Vehicle

The liquid portion of a paint composed mainly of solvents, resins, or oils.

Velvet Construction

Carpet formed by joining the pile, stuffer, and weft yarns with double warp yarns.

Veneer

A thin sheet of material used to cover another surface.

Veneer Gypsum Base

A gypsum board product designed to serve as the base for the application of gypsum veneer plaster.

Veneer Plaster

Calcined gypsum plaster specially formulated to provide specific workability, strength, hardness and abrasion resistance characteristics when applied in thin coats (1/16" to 3/32" nom.) over veneer gypsum base or other approved base. The term thin coat plaster is sometimes used in reference to veneer plaster.

Vent Stack

That part of the soil stack above the highest vent branch.

Vents, Plumbing

Pipes permitting the waste system to operate under atmospheric pressure. They allow air to enter and leave the system, preventing water in the traps from being siphoned off. If this occurs, sewer gases can enter the building.

Vermiculite

An insulation material or aggregate made of expanded mica.

Vertical Load

A load acting in a direction perpendicular to the plane of the horizon.

Vertical Shear

The tendency of one part of a member to move vertically in relationship to the adjacent part.

Viscosity

The resistance of a liquid to flow under an applied load or pressure.

Vitrification

A process of using high kiln temperatures to fuse the surface of grains of clay products so they are impervious to the passage of water.

Volatile Organic Compounds

Compounds released to the atmosphere as a coating dries.

Volt

The unit of potential difference or electromotive force. One volt applied across a resistance of one ohm results in a current flow of one ampere.

Voltage

The force, pressure, or electromotive force that causes electric current to flow in an electric circuit.

Waferboard

A mat-formed panel made of wood wafers randomly arranged and bonded with a waterproof binder.

Wafle Slab

A concrete slab that has ribs running in two directions forming a waffle-like grid.

Wainscot

A protective or decorative finish wall covering applied to the lower part of an interior wall.

Warp

A variation in a board from a flat, plane condition.

Waste Pipe

Horizontal plumbing pipes that connect a fixture to the soil pipe.

Water Repellent

Liquid that penetrates the pores of wood and prevents moisture from penetrating without altering the desirable qualities of the wood.

Water Retention

The property of a mortar that prevents the rapid loss of water by absorption into the masonry units.

Water Stop

A rubber or plastic diaphragm placed across a joint in cast concrete to prevent the passage of water through the joint.

Water Table

The level below the ground where the soil is saturated with water.

Water-Based Coatings

Coatings formulated with water as the solvent.

Water-Cement Ratio

In a concrete or mortar mixture, the ratio fo the amount of water (minus that held by the aggregates) to the amount of cement used.

Water-Smoking

A process used to drive off the remaining water from clay products before they are fired in the kiln.

Water-Struck Brick

Brick made in a mold that was wetted before the clay was placed in the mold.

Water-Vapor Permeability

The rate of water-vapor transmission through a given area of flat material of a given thickness induced by a given vapor pressure difference between the two surfaces under specified temperature and humidity conditions.

Water-Vapor Transmission Rate

The steady-state vapor flow in a given time through a given area of a body, normal to specified parallel surfaces, under specific conditions of temperature and humidity at each surface.

Waterproofing

A material used to make a surface impervious to the penetration of water.

Watt

The unit of measurement of electrical power or rate of work. It is a pressure of one volt flowing at the rate of one ampere.

Wavelength (Sound)

Wave is one complete cycle of sound vibration passing through a medium (such as air) from compression through rarefaction and back to compression again. The physical length of this cycle is termed the wavelength. Wavelengths in air vary from about 1&1/16" for a 20,000-cycle per sec. (see Frequency) sound, to approximately 56&1/2' for a 20-cycle per sec. sound -- the two approximate extremes of human hearing sensitivity. There are waves outside of this range, but generally, they cannot be heard by humans.

Weatherability

The ability of a plastic to resist deterioration due to moisture, ultraviolet light, heat, and chemicals found in the air.

Weathered Joint

A mortar joint finished so the mortar slopes outward, allowing water to shed away from the joint.

Weathering

Changes in the strength, color, surface, or other properties of a material due to the action of the weather.

Weathering Index

A value that reflects the ability of clay masonry units to resist the effects of weathering.

Weathering Steel

A steel alloy that forms a natural self-protecting rust.

Weep Hole

Small openings at the bottom of exterior cavity walls to allow moisture in the cavity to drain out.

Welded-Wire Fabric

A form of steel reinforcing made from wire strands welded where they cross, forming a mesh.

Wet Sand

To smooth a finished joint with a small-celled wet sponge. A preferred method to reduce dust created in the dry sanding method.

WHI

Warnock Hershey International, an independent fire-testing laboratory.

Wilton Construction

Carpet formed on a loom capable of feeding yarns of various colors.

Wind Load

Any load on a building caused by pressure or suction developed by the wind.

Wind Uplift

Upward forces on a building caused by pressure or suction developed by the wind.

Window Wall

A type of metal curtain wall composed of metal framing members containing operable sash, fixed lights, ventilators, or opaque glass panels.