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Term Definition
Bond Breaker

A material used to prevent adjoining materials from adhering.

Bonding Agent

A compound that will hold materials together by bonding to the surfaces to be joined.


The legal recorded property line between two parcels of land.

Box Beam

A structural member of metal or plywood whose cross-section is a closed rectangular box shape.

Box Sill

A type of sill used in frame construction in which the floor joists butt and are nailed to a header joist and rest on the sill.

Braced Frame

A vertical truss used to resist lateral forces.


A pipe in a plumbing system into which no other branch pipes discharge and that discharges into a main or submain.

Branch Circuit

The electrical wiring between the overcurrent protection device and the connected outlets.

Branch Interval

A length of soil or waste stack 8 feet or more in height (equal to one story) within which the horizontal branches from one floor or story of a building are connected to a stack.

Branch Vent

A vent connecting one or more individual vents into a vent stack or stack vent.

Branch, Plumbing

A horizontal run of waste piping that carries waste material to a vertical riser.

Breaking Strength

The point at which a material actually begins to break.

Brick Veneer

Non-loadbearing brick facing applied to a wall to give appearance of solid-brick construction; bricks are fastened to backup structure with metal ties embedded in mortar joints.


Members attached between floor joists to distribute concentrated loads over more than one joist and to prevent rotation of the joist. Solid bridging consists of joist-depth lumber installed perpendicular to and between the joists. Cross-bridging consists of pairs of braces set in an "X" form between joists.

Brinell Hardness

A measure of the resistance of a material to indentation.

Brinnel Hardness Number

A measure of Brinell hardness that is obtained by dividing the load in kilograms by the area of the indentation given in square millimeters.

British Thermal Unit (BTU)

The amount of heat required to raise the temperature of 1 pound (lb) of water by 1 degree Fahrenheit (F).


The characteristic of a material that tends to crack or break without appreciable plastic deformation.

Brown Coat

The second coat of plaster in a three-coat plaster finish.

Buffer Zone

An area separating two different elements or functions.

Buffer, Elevator

Energy-absorbing units placed in the elevator pit.

Buildable Area

The net ground area of a lot that can be covered by a building after required setbacks and other zoning limitations have been accounted for.

Building Code

A set of legal regulations that ensure a minimum standard of health and safety in buildings.

Building Drain

The lowest horizontal piping of a plumbing drainage system that receives the discharge from soil, waste, and other drainage pipes within the building and carries the wasted to the building sewer.

Building Envelope

The enclosure that contains a building's maximum volume.

Building Line

A defined limit within a property line beyond which a structure may not protrude.

Building Sewer

Horizontal piping that carries the waste discharge from the building drain to the public sewer or septic tank.

Built-Up Roof Membrane

A continuous, semi-flexible roof membrane built up fo plies of saturated felts, coated felts, fabrics, or mats that have surface coats of bitumens. The last ply is covered with mineral aggregates, bituminous materials, or a granular-surface roofing sheet.


Curing bricks by placing them in a kiln and subjecting them to a high temperature.


A rigid electric conductor enclosed in a protective busway.


A rigid conduit used to protect a bus running through it.

BX Cable

A cable sheathed with spirally wrapped metal strip identified as Type AC.

Cable Tray

A ladderlike metal frame, open on the top, used to support insulated electrical cables.


Council of American Building Officials Association, made up of representatives from three model codes. Issues National Research Board (NRB) research reports.


A watertight structure within which work can be carried out below the surface of water.

Calcareous Clays

Clays containing at least 15 percent calcium carbonate.

Calcined Gypsum

Ground gypsum that has been heated to drive off the water content.


Curvature built into a beam or truss to compensate for loads that will be encountered when in place and load is applied. The crown is placed upward. Insufficient camber results in unwanted deflection when the member is loaded.


A metric unit of luminous intensity that closely approximates candlepower.


A term used to express the luminous intensity of a light source. It is the same magnitude as a candela.

Cant Beam

Beam with edges chamfered or beveled.

Cant Strip

Triangular section laid at the intersection of two surfaces to ease or eliminate effect of a sharp angle or projection.

Capillary Action

The movement of a liquid through small openings of fibrous material by the adhesive force between the liquid and the material.

Capillary Break

A groove in a member used to create an opening that is too wide to be bridged by a drop of water, thus eliminating the passage of water by capillary action.

Car Safeties, Elevator

Devices used to stop a car and hold it in position should it travel at an excessive speed or go into a free fall.

Car, Elevator

The load-carrying unit of an elevator, consisting of a platform, walls, ceiling, door, and a structural frame.

Carbon Steel

Any steel for which no minimum content for alloying agents is specified, but for which the carbon content is the element used to determine its properties.

Carrying Channel

Main supporting member of a suspended ceiling system to which furring members or channels attach.


Glazed sash or frame hung to open like a door.


The trim around windows, doors, columns or piers.

Cast Iron

A hard, brittle metal made of iron that contains a high percentage of carbon.

Cast-In-Place Concrete

Concrete members formed and poured on the building site in the locations where they are needed.

Cast-In-Place Piles

Concrete piles cast in a hollow metal shell driven into the earth or an uncased hole.


A metal part produced by pouring a molten metal into a mold.

Catch Basin

A drainage device used to collect water, with a deep pit to catch sediment.


A resilient material used to seal cracks and prevent leakage of water.

Cavity Wall

A masonry wall made up of two wythes of masonry units separated by an air space.


A material that is able to unite nonadhesive materials into a solid mass.

Cement Board

A factory-manufactured panel, 1/4" to 3/4" thick, 32" to 48" wide, and 3' to 10' long, made from aggregated and reinforced portland cement.

Cement-Lime Mortar

Mortar made with the addition of slaked lime to the cement.

Cementitious Materials

Materials that have cementing properties.

Central Service Core

A fire-resistant vertical shaft through a multistory building used to route electrical, mechanical, and transportation systems.


The point in a cross-section where all of the area may be considered concentrated without affecting the moment of the area about any axis.


A class of products made of clay fired at high temperatures.

Ceramic Glaze

A compound of metallic oxides, chemicals, and clays fused to a material at high temperature, providing a hard, smooth surface.

Chalk Line

Straight working line made by snapping a chalked cord stretched between two points, transferring chalk to work surface.


A recessed area in a wall for holding pipes and conduit that passes vertically between floors.

Chemical Strengthening

A process for strengthening glass that involves immersing the glass in a molten salt bath.


A refrigerating machine composed of a compressor, a condenser, and an evaporator, used to transfer heat from one fluid to another.

Chord, Bottom

A horizontal or inclined structural member forming the lower edge of a truss.

Chord, Top

A horizontal or inclined structural member forming the top edge of a truss.

Circuit Breaker

An electrical device used to open and close a circuit by nonautomatic means or to open a circuit by automatic means at a predetermined overcurrent without damage to itself.


The flow or movement of people, goods, vehicles, etc., from place to place.


A nonload-bearing exterior wall enclosing a building. It may be brick, aluminum, steel, bronze, plastic, glass, stone, or other acceptable material.

Class A,B,C Roofing

Classification of roofing materials by their resistance to fire when tested in accordance with ASTM E108.


A very cohesive material made up of microscopic particles (less than 0.00008 inches or 0.002 mm).

Clay Tile

A unit made from fired and sometimes glazed clay and used as a finish surface on floors and walls.


Openings in the waste piping system that permit cleaning obstructions from the pipe.

Clear Coating

A transparent protective and/or decorative film.

Clear Span

The horizontal distance between the interior edges of supporting members.

Coal Tar

Tar produced through the destructive distillation of coal during the conversion of coal to coke.

Coal Tar Pitch

A dark brown to almost black hydrocarbon material derived by distilling coke-oven tar.


A paint, varnish, lacquer, or other finish used to create a protective and/or decorative layer.

Coefficient of Heat Transmission (U)

Total amount of heat that passes through an assembly of materials, including air spaces and surface air films. Expressed in Btu per hr., per sq. ft., per °F temperature difference between inside and outside air (beyond the surface air films). "U" values are often used to represent wall and ceiling assemblies, floors and windows. Note: "k" and "C" values cannot simply be added to obtain "U" values. "U" can only be obtained by adding the thermal resistance (reciprocal of "C") of individual items and dividing the total into 1.

Coefficient of Hygrometric Expansion

See Hygrometric Expansion.

Coefficient of Runoff

A fixed ratio of total rainfall that runs off a surface.

Coefficient of Thermal Conductance (C)

Amount of heat (in Btu) that passes through a specific thickness of a material (either homogeneous or heterogeneous) per hr., per sq. ft., per °F. Measured as temperature difference between surfaces. The "C" value of a homogeneous material equals the "k" value divided by the material thickness: C = k/t (where t = thickness of material in inches)

It is impractical to determine a "k" value for some materials such as building paper or those only used or formed as a thin membrane, so only "C" values are given for them.

Coefficient of Thermal Conductivity (k)

Convenient factor represents the amount of heat (in Btu) that passes by conduction through a one inch thickness of homogeneous material, per hr., per sq. ft., per °F. Measured as temperature difference between the two surfaces of the material.

Coefficient of Thermal Expansion

See Thermal Expansion.


A temporary watertight enclosure around an area of water-bearing soil or an area of water from which water is pumped allowing construction to take place in the water-free area.

Cogeneration Systems

Systems using fossil fuel, geothermal energy, wind, or solar energy to produce electricity and heat.


The molecular forces between particles within a body which acts to unite them.

Cohesionless Soil

A soil that when unconfined has little or no cohesion when submerged and no significant strength when air dried.

Cohesive Soil

A soil that when unconfined has considerable cohesion when submerged and considerable strength when air dried.

Cold-Rolled Steel

Steel rolled to the final desired shape at a temperature at which it is no longer plastic.

Collector Street

A street into which minor streets empty and which leads to a major arterial.


Vertical loadbearing member.

Combined Sewer

Sewer that carries both storm water and sanitary or industrial wastes.

Comfort Zone

Any combination of temperature and himidity in which the average person feels comfortable.


Compressing soil to increase its density.

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