Built-Up Roofing System Options
Graveled Surface
This system consists of a traditional roof mat, comprised of four
layers of asphalt moppings and four layers of reinforcing felts.
There are two grades of reinforcing felts—the standard type
IV felt plies can be warranted up to 12 years. Premium type VI
felts have a higher tensive strength, and therefore can be warranted
up to 20 years. Modified bitumen base flashings are installed at
perimeter and curb flashings, adding additional redundancy of crucial
locations. The roof is then flooded with hot asphalt and roofing
gravel is broadcast into the asphalt providing a protective surface
for both traffic and ultra violet rays from the sun.
Modified Bitumen Cap Sheet (Mop in place)
Similar in construction to a built-up roof, the roof mat is comprised
of multiple layers of asphalt and reinforcing felts, either type
IV or type VI, depending on warranty periods. The main difference
is in lieu of the graveling process, the entire roof system including
the field and base flashing locations are covered by a layer of
160 mil mopped in place modified bitumen. This system works well
for mid to high-rise buildings where access is difficult.