Glossary – Dow Protected Membrane Roof EN User Manual

Page 5

Absorption:

the ability of a

material to absorb quantities of
gases or liquids, such as moisture.

Accelerated Weathering:

experimental test where a material
is exposed in a controlled
environment to various elements
(heat, water, condensation or
light) to magnify the effects
of weathering. The material’s
physical properties are measured
before and after the process to
identify any detrimental effects
of weathering.

Aggregate:

rock, stone, crushed

stone, crushed slag or water-
worn gravel used for ballasting
a roof system.

Aging:

the effect on materials

exposed to an environment for
a defined time.

Alligatoring:

the cracking of the

exposed bitumen on a built-up
roof, producing a pattern of cracks
similar to an alligator’s hide.

Asphalt:

a dark brown or black

substance left as a residue when
processing crude oil or petroleum.
Asphalt may be further refined
to conform to various roofing
grade specifications.

Asphalt Emulsion:

a mixture of

asphalt particles and an emulsi-
fying agent, such as bentonite
clay and water.

Ballast:

an anchoring material,

such as stone or precast
concrete pavers, used to hold
insulation and/or roof mem-
branes in place.

Base Ply:

the bottom 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.

Blocking:

sections of wood 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.

Built-up Roof (BUR) Membrane:

a continuous, semi-flexible multi-
ply roof membrane, made up of
plies or layers of saturated felts,
fabrics or mats with bitumen in
between.

Cant Strip:

a beveled or triangular-

shaped strip of wood or other
suitable material used to transi-
tion from the horizontal surface
of a roof deck or rigid insulation
to a vertical surface.

Caulking:

sealing and making

weather-tight the joints, seams
or voids between adjacent units
using a sealant.

Compatible Materials:

two

or more substances that can
be mixed, blended or attached
without separating, reacting or
affecting the materials adversely.

Condensation:

the conversion

of water vapor or other gas to
liquid state as the temperature
drops or atmospheric pressure
rises. (Also see Dew Point.)

Counterflashing:

formed metal

sheeting secured on or into
another surface used to protect
the upper edge of the membrane
or underlying metal flashing
and associated fasteners from
exposure to the weather.

Curb:

a raised roof location

relatively low in height.

Dead Load:

permanent non-

moving load that results from the
weight of a building’s structural
and architectural components,
mechanical and electrical
equipment, and the roof
assembly itself.

Deck:

a structural component of

the roof of a building designed
to safely support the design dead
and live loads, including the
weight of the roof systems, and
the additional live loads required
by the governing building codes.
Decks are either non-combustible
(e.g., corrugated metal, concrete
or gypsum) or combustible (e.g.,
wood plank or plywood) and are
the substrate used to apply the
roofing or waterproofing system.

Design Load:

load specified

in building codes or standards
published by federal, state,
county or city agencies, or in
owners’ specifications to be
used in the design of a building.

Dew Point:

the temperature

where water vapor condenses
in cooling air at the existing
atmospheric pressure and
vapor content. Cooling at or
below the dew point will cause
condensation.

Dynamic Load:

any load that is

non-static, such as a wind load
or a moving live load.

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Glossary