Roofing Terminology
(Click on a letter to learn more)
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Backnailing
The practice of blind nailing (in addition to hot mopping) all the plies of a substrate to prevent slippage.
Ballast
An anchoring material, such as aggregate, precast pavers, which employ the force of gravity to hold (or assist in holding) membranes in place.
Base Ply
The base ply is the first ply when it is a separate ply and not part of a shingled system.
Base Sheet
A saturated or coated felt placed as the first ply in some multi-ply built up roof membranes.
Bentonite
A clay formed from decomposed volcanic ash, with a high content of the mineral montmorillonite; has the capacity of absorbing a considerable amount of water, and swells accordingly.
Bitumen
The generic term for an amorphous, semi-solid mixture of complex hydrocarbons derived from any organic source. Asphalt and coal tar are the two used in the roofing industry.
Bituminous
Containing or treated with bitumen. Examples: bituminous concrete, bituminous concretes, bituminous felts and fabrics, bituminous pavement.
Bituminous Grout
A mixture of bituminous material and fine sand that will flow into place without mechanical manipulation when heated.
Blind Nailing
The practice of nailing the back portion of a roofing ply.
Blister
A spongy raised portion of a roof membrane, ranging in area from 1 inch in diameter and of barely detectable height upward. Blisters result from the pressure buildup of gases entrapped in the membrane system. these gases most commonly are air and/or water vapor. Blisters usually involve delamination of the underlying membrane plies.
Bond
The adhesive and cohesive forces holding two roofing components in intimate contact.
Boot
Covering of flexible material, which may be preformed to a particular shape, used to seal around a penetration.
Brooming
Embedding a ply of roofing material by using a broom to smooth out the ply and ensure contact with the adhesive under the ply.
British Thermal Unit (BTU)
The heat energy required to raise the temperature of 1 pound of water 1 degree Fahrenheit.
Buckle
An upward, elongated tenting displacement of a roof membrane frequently occurring over insulation or deck joints. A buckle may be an indication of movement within a roof assembly, and usually associated with improper installation.
Built-up Roof Membrane
A continuous, semi-flexible roof membrane assembly, consisting of plies of saturated felts, coated felts, fabrics or mats between which alternate layers of bitumen are applied, generally surfaced with mineral aggregate, bituminous materials, or a granule-surfaced roofing sheet.
Butyl
A rubber like material produced by copolymerizing isobutylene with a small amount of isoprene, Butyl may be manufactured in sheets, or blended with other elastomeric materials to make sealants and adhesives.
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