BOABC Level 2 flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Dead load

The vertical load produced by the weight of permanent construction, including structure, finishes, partitions, and fixed equipment. It is treated as a constant service load in design calculations.

Live load

The occupancy-dependent load from people, furniture, and movable equipment. It is specified by use group in the building code and is not reduced below code minimums regardless of actual occupancy.

Load combination

A factored or unfactored set of loads applied simultaneously to check a structure. Allowable stress design uses service combinations; strength design multiplies each load by a load factor.

Allowable bearing pressure

The maximum soil pressure a foundation may impose without excessive settlement or shear failure. Footing area equals total service load, including footing weight, divided by this pressure.

Deflection limit

A maximum permissible sag expressed as a fraction of span, such as L/360. The ratio is selected according to whether the member supports brittle finishes, general floors, or nonceiling roofs.

Means of egress

A continuous, unobstructed path from any point in a building to a public way. It comprises the exit access, the exit, and the exit discharge, and each portion has its own width and rating rules.

Travel distance

The measured length along the egress path from the most remote point in a space to the nearest exit. Codes cap it by occupancy, and it is measured along the natural walking path.

Fire-resistance rating

The time in hours an assembly resists fire under a standardized test. It applies to the complete assembly, including supports and penetrations, not to an individual material alone.

Thermal bridging

Heat flow that bypasses insulation through framing, shelf angles, or other conductive members. It lowers the effective R-value of the whole assembly below the cavity insulation value.

U-factor

The overall rate of heat transmission through an assembly per unit area and temperature difference. It is the reciprocal of assembly R-value and is area-weighted across components.

Vapor retarder

A material that limits water vapor diffusion through an assembly. Its placement depends on climate, and it is installed on the warm side of the insulation in cold climates.

Air barrier continuity

An unbroken plane that resists uncontrolled air leakage through the envelope. It must be sealed at joints, penetrations, and transitions between wall, roof, and foundation assemblies.

Footing

The widened base of a foundation that spreads the column or wall load over sufficient soil area. Its width is set by allowable bearing pressure and total service load.

Slab-on-grade

A concrete slab placed directly on prepared soil and used as a floor. It typically includes a vapor retarder and granular base beneath it and may carry thickened edges at load-bearing walls.

Occupant load

The computed number of people a space is designed to hold. It equals floor area divided by an occupant-load factor and drives egress width, exits, and fixture counts.

Drainage fixture unit

A relative measure of the waste-flow load a fixture imposes on a drainage system. Pipe sizing tables relate accumulated fixture units to allowable drain diameter and slope.

Water supply fixture unit

A relative measure of the demand a fixture places on the water distribution system. It accounts for flow rate, duration, and frequency of use when sizing supply piping.

Trap seal

The water retained in a fixture trap that blocks sewer gas. Common codes require a depth between 2 and 4 inches, maintained by venting and by limiting evaporation.

Fixture vent

A pipe that admits air to a drainage system near a trap and lets sewer gas escape outdoors. Each trap must be vented, and the arm length is limited by pipe size.

Stack vent

The extension of a soil or waste stack above the highest fixture branch to the open air. It relieves pressure in the stack and protects trap seals on the fixtures served.

Building drain

The lowest horizontal piping of a drainage system that receives waste from soil and waste stacks. It conveys flow to the building sewer, which begins outside the building wall.

Building sewer

The pipe that carries sewage from the building drain to the public sewer or private disposal system. It begins at the point where the drain exits the building.

Drainage slope

The fall per unit length required for gravity flow in a drain. Common code values are 1/4 inch per foot for 2-inch pipe and 1/8 inch per foot for 3-inch and larger pipe.

Residual pressure

The water pressure remaining at a fixture while it is flowing. Codes require a minimum, often about 8 psi, so fixtures operate correctly without excessive supply pipe sizing.

Pressure-reducing valve

A device that lowers incoming water pressure to a safe downstream value. It is typically required when static pressure exceeds about 80 psi to protect fixtures and piping.

Water hammer

A pressure surge caused by a sudden stop in flow at a quick-closing valve. Arrestors with trapped air or mechanical chambers absorb the shock near the source.

Backflow prevention

Protection against reverse flow that could contaminate the potable supply. Air gaps provide the highest protection; reduced-pressure-zone assemblies serve high-hazard connections.

Air gap

An unobstructed vertical separation between a supply outlet and the flood-level rim of a fixture. It is the most reliable backflow protection because no mechanical part can fail.

Water heater relief valve

A temperature-and-pressure relief device that discharges near the floor or to a safe location. It prevents tank rupture from overheating or excessive pressure and must not be capped.

Expansion tank

A vessel that absorbs the volume increase of heated water in a closed system. It prevents excess pressure from damaging piping and fixtures and is installed on the cold supply side.

Cleanout

An accessible fitting that allows a drain to be rodded or inspected. Codes require them at the base of stacks, at changes in direction, and at intervals along long horizontal runs.

Flood-level rim

The edge of a fixture over which water would overflow onto the floor. It sets the required height of the air gap and the location of backflow prevention devices.