Generally all slopes higher than 4/12 are considered steep slope.
Steep Slope Roofing usually refers to roofing materials suitable for roofs that have slopes of 3:12 or greater. These include asphalt roll roofing as well as asphalt shingles, concrete and clay tiles, wood shakes, slate and metal roofs. Additionally, some of the modified bituminous roofing as well as certain adhered single ply membranes and SPF foam can also be used in certain steep slope roofing applications.
The most common steep slope roofing types are asphalt shingles, concrete and clay tiles and wood shakes and are most often associated with residential construction but can also be used for steep sloped commercial roofing as well. Metal roofing is used in both steep slope and low slope roofing applications.
Asphalt shingles comprise the largest segment of steep slope roofing. They are composed of fibrous glass mats impregnated with asphalt. Because asphalt is easily degraded by UV exposure, a surfacing of varying colored mineral granules is embedded into the exposed side of the asphalt shingle that also imparts its finished color. Shingles are overlapped and secured by nailing through the roof overlay of felts or roof paper into the roof deck from the bottom of the roof slope to the high point of the roof referred to as the ridge. Special ridge vents are usually installed to provide ventilation from the attic space.
In certain parts of the country, concrete or clay tiles are installed in overlapping "shingle fashion" on steep slope roofs as well. These tiles are usually installed with a combination of nails and cementitious mortar.
Wood shakes are also popular in many parts of the country and are nailed in "shingle fashion" over a roof felt and usually into a wood deck. The downside to using wood shakes is their lack of significant fire resistance and their propensity to mold and moss growth in wet, humid climates.
A growing segment of the roofing industry is metal roofing. The various types of metal roofs include metal shingles as well as long spans of metal panels. Metal panels are easily installed on steep roofs and are becoming more popular for their aesthetics and inherent fire resistance and are common in both residential and commercial construction.