Asphalt roll roofing
Asphalt roll roofing is an inexpensive roofing material commonly used for utility buildings in North America. The material is based on the same materials used in asphalt shingles; an organic felt or fiberglass mat, saturated with asphalt, and faced with granular stone aggregate.[1] 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 cm) by 33 feet (10 m) in size.[2] 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 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.[3]
Contents
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 comon method on sheds.
- Torch on - underside of felt melted with a torch and pressed in place
References
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- ↑ "What is roll roofing?". All About Roofing. Asphalt Roofing Manufacturers Association. 2009. Retrieved 2009-06-18.
- ↑ "Mineral Surfaced Roll". Owens Corning Roofing. 2009. Retrieved 2009-06-18.
- ↑ "2" and 4" Selvedged Mineral Surface Roll Roofing Application Instructions" (PDF). Owens Corning Roofing and Asphalt, Inc. 2008. Retrieved 2009-06-18.
