Modified Bitumen Roofing Installation
Base sheets are usually the first piece of Built-Up Roofing material installed and are usually mechanically-fastened (nailed) to the deck or substrate. Felt layers can be installed with hot asphalt, coal tar, or cold-applied liquid adhesive (solvent-based asphalt or "cutback" asphalt.) The surfacing is the same amount of bitumen, or lap cement used to install the cap sheet as is used to install the plies.
The service life of a roof is dependent on many factors: geographical location & weather conditions, foot traffic, materials used, conditions under which the roof was installed, slope of roof, type of surfacing material, etc. Under ideal conditions, a 3-ply built-up roof should last at least fifteen years, a 4-ply should last at least 20 years, and a 5-ply should last at least 25 years.