There are a variety of different cover board
material types available. These are some of the
most popular cover board options and their specific
benefits.
Fiber Board
One of the most widely used cover board materials,
this board is often made from wood fiber or bagasi
(sugar cane). Fiber board has a porous nature,
good compressive and flexural strength, and an
affinity for moisture, making it a popular choice
under many membrane systems. However, fiber board
is susceptible to moisture absorption, which leads
to strength loss, decay or rot when it is exposed
to moisture for extended periods of time.
Perlite Roof Board
This roof board is composed of expanded perlite
ore, cellulose fibers, asphalt and starch binders.
Traditionally, it has been coated on the top side
surface with an emulsion to inhibit excessive
absorption of the mopping asphalt. This roof board
provides a dimensionally stable and thermally
resistant surface for the application of hot-applied
roofing membranes. It exhibits excellent flame
spread characteristics, which may be important
in the design and installation of some roof assemblies.
Like fiber board, perlite cover board is sensitive
to moisture.
Glass/Mineral Fiber Board
Glass and mineral fiber board is made from fiberized
glass or basalt rock bonded with resinous binders
and compressed to various densities. To prevent
absorption of adhesives or asphalt into the porous
core, a facer is applied at the factory. Some
manufacturers provide boards with special facers
designed for the direct application of torched-on
modified bitumen membranes. The product is dimensionally
stable and has a high degree of heat resistance.
While generally unaffected by moisture, glass
and mineral fiber insulation can lose its structural
integrity if it remains wet for long periods of
time. In addition, the facers may be adversely
affected by exposure to moisture. Due to the inherent
absorptive nature of its bottom surface, it cannot
be back-mopped with hot asphalt for securement
over heat-sensitive insulations.
Asphaltic Core Boards
Developed in recent years, this type of cover
board is often fabricated with an ashphaltic core
sandwiched between a glass fiber reinforcement.
Asphaltic cover boards are designed for use primarily
with hot-applied asphalt membranes and torch-on
systems. Highly resistant to moisture, they are
compatible with all asphaltic systems. However,
the asphalt content makes the board unsuitable
for use under single-ply membranes, which are
affected adversely by contact with asphalt.
Glass Mat-Faced Gypsum
Board
This type of board employs glass mat facings front
and back that are embedded into a water-resistant
treated core, providing moisture and fire resistance.
Fiber-Reinforced Gypsum
Panels
This innovative new type of fiber-reinforced gypsum
panel incorporates the latest cover board technology.
The cover board provides exceptional resistance
to both mold and moisture, along with outstanding
fire performance. This high-performance product
is manufactured with no face layers, providing
excellent wind uplift properties. The product
also features a high compressive strength (up
to 20 times greater than wood fiber board or perlite),
enabling it to protect the roofing system from
potential damage from foot traffic or hail. It
is also made from 95 percent recycled materials.
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