Insulation. See Thermal Insulation.
Laitance. Weak material, consisting principally of lime, that is
formed on the surface of concrete, especially when excess water
is mixed with the cement.
Loose-laid roof system. Design concept in which insulation
boards and/or membrane are not anchored to the deck but ballasted
by loose aggregate or concrete pavers.
Lap. The dimension
that a felt covers an underlying felt or
sheet in a multiple
built-up bituminous membrane or single-ply
membrane. Edge lap
indicates the transverse cover; end lap
indicates the cover
at the end of the roll.
Mat. Flexible, heat-cured sheet made of inorganic fibers and a
Membrane. A flexible or semi-flexible roof covering, the
waterproofing component of the roof system.
Mineral granules. Natural or synthetic aggregate particles,
ranging in size from 500 microns (1 micron = 10-6 meter) to 1/4-
inch diameter, used to surface cap sheets, asphalt shingles, and
some cold-process membranes and modified bitumens.
Mineral-surfaced sheet. Asphalt-saturated felt, coated on one or
both sides and surfaced with mineral granules.
Monomer. Class of molecules with molecular weight ranging
roughly between 30 and 250, capable of combining into huge,
polymeric macromolecules, l00 to l0,000 times as large as the
basic monomeric molecules, through chainlike repetition of the
basic monomeric chemical structure.
Mop-and-flop. A technique which roof system components
(insulation boards, felt plies, cap sheets, etc.) are first
placed upside down adjacent to their final locations, coated with
adhesive, and turned over and adhered to the substrate (a
generally bad practice).
Mopping. Application of hot, fluid bitumen to substrate or to
plies of built-up membrane with a manually wielded mop or a
A continuous coating.