Back-Nailing: (also referred to as Blind-Nailing) the practice of nailing the back portion of a roofing ply, steep roofing unit, or other components in a manner so that the fasteners are covered by the next sequential ply, or course, and are not exposed to the weather in the finished roof system.

 

Ballast: an anchoring material, such as aggregate, or precast concrete pavers, which employ the force of gravity to hold (or assist in holding) single-ply roof membranes in place.

 

Base Flashing (membrane base flashing): plies or strips of roof membrane material used to close-off and/or seal a roof at the roof-to-vertical intersections, such as at a roof-to-wall juncture. Membrane base flashing covers the edge of the field membrane. (Also see Flashing.)

 

Base Ply: the lowermost ply of roofing in a roof membrane or roof system.

 

Base Sheet: an impregnated, saturated, or coated felt placed as the first ply in some multi-ply built-up and  modified bitumen roof membranes.

 

Batten: (1) cap or cover; (2) in a metal roof: a metal closure set over, or covering the joint between, adjacent metal panels; (3) wood: a strip of wood usually set in or over the structural deck, used to elevate and/or attach a primary roof covering such as tile; (4) in a membrane roof system: a narrow plastic, wood, or metal bar which is used to fasten or hold the roof membrane and/or base flashing in place.

 

Batten Seam: a metal panel profile attached to and formed around a beveled wood or metal batten.

 

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.

 

Bermuda Seam: a metal panel profile featuring a step-down profile that runs perpendicular to the slope of the roof.

 

Bird Screen: wire mesh used to prevent birds from entering the building through ventilators, louvers, or other openings. (See Insect Screen.)

 

Bitumen: (1) a class of amorphous, black or dark colored, (solid, semi-solid, or viscous) cementitious sub-stances, natural or manufactured, composed principally of high molecular weight hydrocarbons, soluble in carbon disulfide, and found in petroleum asphalts, coal tars and pitches, wood tars and asphalts; (2) a generic term used to denote any material composed principally of bitumen, typically asphalt or coal tar.

 

Bitumen-Stop: see Envelope and Bleed Sheet.

 

Blackberry (sometimes referred to as Blueberry or Tar-Boil): a small bubble or blister in the flood coating of an aggregate-surfaced built-up roof membrane.

 

Blanket (Batt) Insulation: fiberglass or other compressible fibrous insulation, generally available in roll form.

 

Bleed-Sheet: a sheet material used to prevent the migration of bitumen.

Blind-Nailing: the use of nails that are not exposed to the weather in the finished roofing system.

 

Blister: an enclosed pocket of air, which may be mixed with water or solvent vapor, trapped between impermeable layers of felt or membrane, or between the membrane and substrate.

 

Blocking: sections of wood (which may be preservative treated) built into a roof assembly, usually attached above the deck and below the membrane or flashing, used to stiffen the deck around an opening, act as a stop for insulation, support a curb, or to serve as a nailer for attachment of the membrane and/or flashing.

 

BOCA: Building Officials and Code Administrators, International, Inc. (author of the BOCA National BuildingCode).

 

Boot: (1) a covering made of flexible material, which may be preformed to a particular shape, used to exclude dust, dirt, moisture, etc. from around a penetration; (2) a flexible material used to form a closure, sometimes installed at inside and outside corners.

 

Brake: hand- or power-activated machinery used to form metal.

 

Bridging: when the membrane is unsupported at a juncture.

 

British Thermal Unit (BTU): the heat energy required to raise the temperature of one pound of water one degree Fahrenheit (joule).

 

Brooming: an action carried out to facilitate embedment of a ply of roofing material into hot bitumen by using a broom, squeegee, or special implement to smooth out the ply and ensure contact with the bitumen or adhesive under the ply.

 

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 the roof assembly.

 

Building Code: published regulations and ordinances established by a recognized agency prescribing design loads, procedures, and construction details for structures. Usually applying to designated jurisdictions (city, county, state, etc.). Building codes control design, construction, and quality of materials, use and occupancy, location and maintenance of buildings and structures within the area for which the code has been adopted.

 

Built-Up Roof Membrane (BUR): a continuous, semi-flexible multi-ply roof membrane, consisting of plies or layers of saturated felts, coated felts, fabrics, or mats between which alternate layers of bitumen are applied. Generally, built-up roof membranes are surfaced with mineral aggregate and bitumen, a liquid-applied coating, or a granule-surfaced cap sheet.

 

Butt Joint: a joint formed by adjacent, separate sections of material, such as where two neighboring pieces of insulation abut.

 

Butyl: 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.

 

Butyl Tape: a sealant tape sometimes used between metal roof panel seams and end laps; also used to seal other types of sheet metal joints, and in various sealant applications.

 

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