Roll Roofing

Roll roofing is a bitumen roofing product made from the same basic materials as asphalt shingles, a felt or glass-fibre mat saturated and coated with asphalt and surfaced with mineral granules, but supplied as continuous rolls rather than cut shingles. It is designed to be left exposed to the weather and is one of the cheapest roof coverings available.

Uses

Roll roofing is typically used on sheds, garages, porches, farm buildings and other structures where appearance and long life are less important than cost. It is also used in valleys and as an underlayer in some built-up systems. In the United Kingdom and Ireland, the similar product is commonly called shed felt or mineral felt.

Slope

In US model codes, mineral-surfaced roll roofing can be used on slopes as low as 1:12 (about 4.8°), lower than the 2:12 minimum for asphalt shingles. On these shallow slopes the laps are sealed with cement or adhesive.

Variants

• Nail-down roll roofing: laid in overlapping courses and fastened with roofing nails, with laps sealed using lap cement.
• Self-adhesive rolls: with a release film over the adhesive.
• Torch-on rolls: modified-bitumen products melted into place with a gas torch; these are usually classed as low-slope membranes rather than simple roll roofing.

Limitations

Because it is a single thin layer with lapped seams, roll roofing generally has a shorter service life than shingles or multi-ply membranes. Heat and ultraviolet light age the asphalt, and the long seams are vulnerable to wind and to thermal movement. It is not generally used on homes where appearance matters.

Relationship to roofing felt

Plain roofing felt (for example, US "#15" and "#30" felts under ASTM D226) is a similar asphalt-saturated sheet but without a granule surface; it is meant as an underlayment, not as an exposed finish.