Ballast: a material, such as aggregate or precast concrete pavers, which employs its mass and 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 horizontal-to-vertical intersections, such as a roof-to-wall juncture. Membrane base flashing covers the edge of the field membrane.
Base ply: the bottom or first ply in a built-up roof membrane when additional plies are to be subsequently installed.
Base sheet: an impregnated, saturated, or coated felt placed as the first ply in some low-slope roof systems.
Batten: (1) cap or cover; (2) in a metal roof, a metal closure set over, or covering the joint between, adjacent metal panels; (3) in a wood roof, 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 single ply membrane roof system, a narrow plastic, wood or metal bar that 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.
Bird bath: random, inconsequential amounts of residual water on a roof membrane.
Bitumen: (1) a class of amorphous, black or dark colored, (solid, semi-solid or viscous) cementitious substances, natural or manufactured, composed principally of high molecular weight hydrocarbons, soluble in carbon disulfide, and found in asphalts, tars, pitches, and asphaltenes; (2) a generic term used to denote any material composed principally of bitumen, typically asphalt or coal tar.
Bituminous emulsion: a suspension of minute particles of bituminous material in water.
Blackberry (also referred to as “Blueberry” or “Tar-boil”): a small bubble or blister in the flood coat of an aggregate-surfaced built-up roof membrane.
Blister: an enclosed pocket of air, which may be mixed with water or solvent vapor, trapped between impermeable layer of felt or membrane, or between the membrane and substrate.
Blistering: bubbles or pimples in roofing materials usually moisture related. In shingles blisters are either moisture under the material or moisture trapped inside the material.
Blueberry: a small bubble found in the flood coat of an aggregate-surfaced built-up roof. See Tar boil.
Bond: the force(s) holding two components in positive contact.
Bonding agent: a chemical agent used to create a bond between two layers.
Boot: a piece of material preformed to protect roof penetrations from dirt, moisture and other foreign and/or damaging substances.
Brooming: embedding a ply of roofing material into hot bitumen or adhesive by using a broom, squeegee, or other piece of equipment to eliminate voids and help ensure adhesion.
Buckle: a long, tented displacement of a roof membrane. Can occur over insulation and deck joints.
Built-up roof membrane: a roof membrane consisting of layers of bitumen, which serves as the waterproofing component, with plies of reinforcement fabric installed between each layer. The reinforcement material can consist of bitumen-saturated felt, coated felt, polyester felt or other fabrics. A surfacing in generally applied and can be asphalt, aggregate, emulsion, or a granule-surfaced cap sheet.
BUR: an acronym for Built-Up Roof.
Butyl tape: a sealant tape used in numerous sealant applications such as sealing and sheet metal joints.