Single-ply membrane. A membrane, either sheet or fluid-applied,
with only a single layer of material designed to prevent water
intrusion into the building.
Skater's cracks. Curved cracks observed in smooth-surfaced
Slag. Porous aggregate used as built-up bituminous membrane
surfacing, comprising silicates and alumino-silicates of calcium
and other bases, developed with iron with a blast furnace.
Slippage. Relative lateral movement of adjacent felt plies in a
membrane. It occurs mainly in sloped roofing membranes, exposing
the lower plies, or even the base ply, to the weather.
Slope. The tangent of the angle between the roof surface and the
horizontal, in inches per foot. The Asphalt Roofing
Manufacturers' Association ranks slopes as follows:
Level: 1/2-inch maximum
Low slope: over 1/2 inch up to 1-1/2 inches
Steep slope: over 1-1/2 inches
Smooth-surfaced roof. A roofing membrane surfaced with a layer
of hot-mopped asphalt or cold-applied asphalt-clay emulsion or
asphalt cutback, or sometimes with an unmopped, inorganic felt.
Softening point. Temperature at which bitumen becomes soft enough
to flow, as measured by standard laboratory test in which a steel
ball falls a measured distance through a disk made of the tested
Softening point drift. Change in softening point from temperature
change during storage or application (see also Fallback).
Membrane tear resulting from tensile stress.
Spudder. Heavy steel implement with a dull, bevel-edged blade
designed to remove embedded aggregate from a membrane surface
(also called a Scraper).