Alarm Signal: A signal indicating an emergency, such as a fire, requiring immediate action.

Alligatoring: An oxidized condition of aged surfacing bitumen, asphalt, or other low-slope roof surface that has lost its volatile oils due to exposure to sun and solar radiation, which is the ultimate result of the surface’s limited tolerance to thermal expansion and contraction. Alligatoring is characterized by a coarse, checked pattern of cracks resembling an alligator hide.

Alteration: Any construction or renovation to an existing structure other than a repair or addition; also, a change in a mechanical system.

Ambulatory: Able to walk without accommodation.

Antimicrobial: Agent that kills microbial growth. See “disinfectant,” “sanitizer”, and “sterilizer.”

Appliance: Utilization equipment, generally other than industrial, that is installed or connected as a unit to perform one or more functions.

Approved: Acceptable to the authority having jurisdiction; also, accepted by an internationally recognized organization, such as InterNACHI.

arc-fault circuit interrupter (AFCI): a device intended to provide protection from the effects of arc faults by recognizing characteristics unique to arcing, and by functioning to de-energize the circuit when an arc fault is detected.

ASHRAE: American Society of Heating, Refrigerating, and Air-Conditioning Engineers

ASTM: American Society for Testing and Materials

Atactic Polypropylene (APP): Used as a modifying compound in the asphalt membrane of modified bitumen (MB) roofs; exhibits a plasticized nature.

Authority Having Jurisdiction (AHJ): An organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment, materials, an installation, or a procedure.   The AHJ is often the building owner, health department, insurance agent, or fire marshal.

Automatic: That which provides a function without the necessity of human intervention.

Automatic Fire-Extinguishing System: A system of devices and equipment that automatically detects a fire and discharges in an attempt to put it out.

Automatic Sprinkler System: An automated sprinkler system for fire-protection purposes.

Back Span: A piece of the cantilever joist or rafter that extends within the supporting wall.

Backdrafting: A venting disturbance occurring from the reversal of the normal flow of air, allowing exhaust to be pulled back into a building instead of through the venting system.

Balcony: Exterior floor projecting from and supported by a structure without additional independent supports.

Ballast: A material similar to aggregate or pavers (smooth river stone, crushed stone, concrete pavers, lightweight concrete pavers, etc.) that is often used as a weight on loose-laid roofing systems to hold the membrane in place.

Ballast Scouring: A term used to describe the shifting of ballast or loosened pavers on the exposed surface of a roof, usually as the result of wind.

Band Joist: Dimensional lumber used as a perimeter joist of the building framing.

Barrel Vault: An architectural element that is formed by the extrusion of semi-cylindrical curves. It may appear as a series of arches.

Barrier Curb: A curb in a parking area that is high enough to block vehicles from traveling over the top. They protect buildings and pedestrians from impact.

Base Flashing: The upturned edge of a watertight membrane formed at a roof's termination point by the extension of the felts vertically over the cant strip and up the wall, and secured with mechanical fasteners.

Basement: That portion of a building which is partly or completely below grade.

Basement Wall: A wall of a building that is mostly below grade.

Bathroom: A room containing plumbing fixtures, such as a water closet, urinal, bathtub and/or shower.

Batten: A general term used to describe a cap or covering. In a singly-ply membrane installation, it’s a narrow bar used to hold the roof membrane and/or base flashing in place.

Beam: A horizontally placed primary structural support member (of steel, concrete, lumber, etc.) transversely supporting a load that transfers weight from one location to another. It’s often supported by posts, exterior walls, or foundational elements.

Bearing Wall: A bearing wall, or a load-bearing wall, is designed to carry the weight of structural components above, through itself, and to the supporting components below.

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