01 May 1999
GLOSSARY OF ROOFING RELATED TERMS
Base sheet--A saturated or coated felt placed
Aggregate--(1) Crushed stone, crushed slag, or
as the first ply in a multi-ply bituminous roofing
water-worn gravel used for surfacing a built-up
roof; (2) Any granular mineral material.
Batten--Raised rib, in a metal roof, or a
Alligatoring--Shrinkage cracking of the surfacing
separate part or formed portion in a metal
bitumen on a built-up roof, producing a pattern
similar to an alligator's hide. The cracks may or
may not extend through the entire surfacing
Beaufort scale--A scale in which the force of the
wind is indicated by numbers from 0 to 12. No.7
is "near gale" at 52-61 km/h (32-38 m.p.h.). No.
Alloys, polymeric--A blend of two or more
9 is "strong gale" at 76-87 km/h (47-54 m.p.h.).
polymers, e.g., a rubber and a plastic to improve
a given property, e.g., impact strength.
Bitumen--(1) A class of amorphous, black or
dark colored, (solid, semisolid, or viscous)
Asphalt--A dark brown to black cementitious
material whose predominating constituents are
manufactured, composed principally of high
bitumens that occur in nature or are obtained in
molecular weight hydrocarbons, soluble in
carbon disulfide, and found in asphalts, tars,
pitches, and asphaltites; (2) A generic term used
Asphalt felt--An asphalt-saturated felt.
to denote any material composed principally of
bitumen; (3) In the roofing industry there are two
Asphalt, air blown--An asphalt produced by
basic bitumens: asphalt and coal-tar pitch.
blowing air through molten asphalt at an
Before application they are either (a) heated to a
elevated temperature to raise its softening point
liquid state, (b) dissolved in a solvent, or (c)
and modify other properties.
Asphaltene--A high molecular weight hydro-
Bituminous emulsion--A suspension of minute
carbon fraction precipitated from asphalt by a
globules of bituminous material in water or in an
designated paraffinic naphtha solvent at a
specified temperature and solvent-asphalt ratio.
Note--The asphaltene fraction should be
Bituminous, adj.--Containing or treated with
identified by the temperature and solvent-
bitumen. Examples: bituminous concrete,
asphalt ratio used.
bituminous felts and fabrics, bituminous
Atactic--A chain of molecules in which the
position of the side methyl groups is more or
less random. (Amorphic; Low Crystallinity)
form, often installed between metal roof panels
Backup plate--A rigid plate to support an end
lap to provide uniform compression.
Blister--An enclosed pocket of air-water vapor,
trapped between membrane plies or between
Backnailing--blind (i.e., concealed by over-
membrane and substrate.
lapping felt) nailing of roofing felts to a substrate
in addition to hot-mopping to prevent slippage.
rounded delamination of the surface of a
Ballast--Loose aggregate, concrete pavers, or
other material designed to prevent wind uplift or
either more or less sharply defined.
flotation of a loose-laid roof system.