Asphalt roll roofing or membrane is an inexpensive roofing material commonly used for buildings that feature a sloped roof pitch in North America. The material is based on the same materials used in asphalt shingle

Asphalt shingle

An asphalt shingle is a type of roof shingle. They are one of the most widely used roofing covers because they are relatively inexpensive and fairly simple to install.-Types:...

s; an organic felt or fiberglass mat, saturated with asphalt

Asphalt

Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...

, and faced with granular stone aggregate. Roll roofing is usually restricted to a lightweight mat compared to shingles, as it must be rolled for shipment. Rolls are typically 36 inches (91.4 cm) by 33 feet (10.1 m) in size. Due to its light weight compared to shingles, roll roofing is regarded as an inexpensive, temporary material. Its wide width makes it vulnerable to temperature-induced tearing as it expands and contracts.

Roll roofing is normally applied parallel to the eaves

Eaves

The eaves of a roof are its lower edges. They usually project beyond the walls of the building to carry rain water away.-Etymology:"Eaves" is derived from Old English and is both the singular and plural form of the word.- Function :...

from the bottom of the roof upwards, lapping each new roll in the same manner as shingles. Its use is restricted to roofs with a pitch of greater than 2:12. To avoid penetrating the exposed membrane with nails, adhesive, or "lap cement" must be used at the bottom edge to keep it from being lifted by the wind. The upper edge of the roll is nailed and covered by the next roll.

Uses

The main uses are:

• for outbuildings
• on flat roofs on houses in the UK, a low cost limited life roofing method
• as a backup water catching & wind stopping layer under roofing slates & tiles

Types

Several variations of bitumen roofing felt are available.

Fibre content:

• mixed rag fibre - lowest cost, shortest life
• all plastic fibres
• fibreglass - longest lived

Bitumen:

• bitumen - stiffens & hardens in winter, cracks in time
• modified bitumen - stays supple in winter, lasts better

Underside:

• Uncoated - most common, applied with adhesive or nails
• Self adhesive - simpler to apply
• Torchable - applied by torching the underside, which partly melts and glues the sheet. (Most roofing felt is torchable.)

Topping:

• Sand - low cost
• Stone waste - prettier, better life expectancy. Only used on capsheet.
• Uncoated - used as undersheet

Application methods

• Glue in place with bitumen/solvent mix
• Nail in place - relies on the clout nail head being driven slightly under the surface for a pressure seal. Waterproofing not quite perfect, a water durable timber layer is used under the felt, usually OSB or ply. Most common method on sheds.
• Hot bitumen
• Torch on - underside of felt melted with a torch and pressed in place