Pitched or sloped roofs range from a moderately sloped 3-in-12 pitch to the 45-degree angle 12-in-12 slope commonly seen on A-frame roofs. Even steeper are many mansard roofs and parts of gambrel roofs, such as on barns, which may have 20-in-12 pitches. Roofing material for pitched roofs include the following:
- Composition shingles: Generically called asphalt shingles, these cover 70% of all roofs in this country. Composition shingles are divided into two types, organic or fiberglass. Organic composition roofs are manufactured with a cellulose fiber base made from recycled paper and wood fibers. This base is then saturated with asphalt and given a mineral coating on one side to resist weathering. Fiberglass shingles are made in a similar fashion but the central core is fiberglass, which is more flexible and stronger than the cellulose materials. Composition shingles are manufactured in a wide variety of colors and are rated by their projected life expectancy, typically 20, 25, and 30 years. Most roofing manufacturers warranty their roofs for these periods, but only if their certified roofers install them. Otherwise, the manufacturers disallow any guarantees.
- Dimensional shingles: These are made from the same material as organic or fiberglass composition shingles but are much thicker. The additional layers may be sculpted to provide attractive shadow lines that give the roof a customized appearance. The extra thickness also increases their life expectancy, up to 40 years. As with composition shingles, the manufacturer's warranty generally applies only if one of their certified roofers installs the material.
- Wood shingles: Shingles are commonly sawn from Western red cedar, chosen for its natural resistance to decay. Shingles are sold as No. 1, 2, or 3. Use only No. 1 for roofing because it is cut from knot-free heartwood. No. 2, from less resistant sapwood, is acceptable for siding. Shingles come in 16-, 18-, and 24-inch lengths and are sold in bundles, with four bundles to a square (100 square feet).
- Wood Shakes: Like shingles, shakes are mostly cut from cedar logs. Shakes are either resawn or hand-split. A resawn shake has one side sawn to give it a more precise taper while leaving the exposed side with the typical irregular shake appearance. Hand-split shakes are more irregular but still tapered. Shakes are graded by weight: heavy or medium. They are sold in 18- or 24-inch lengths, with five bundles of 24-inch shakes covering 100 square feet with a 10-inch exposure. Most communities now require that roofing shakes or shingles be pressure-treated with a fire retardant prior to installation. Check your local codes if considering such a roof.
- Tile roofs: The familiar Spanish or mission tiles are commonly made from clay or concrete. Tile shapes include the half-barrel, S-shape, interlocking, and flat. Although tiles have a life span of 50 to 100 years, they are heavy and can only be applied to roofs constructed to support such weight. Tiles are usually fitted on spaced 2-by-6 boards nailed to solid plywood roof sheathing. For steep slopes, code may require that the tiles be nailed in place through predrilled holes or supported with metal brackets.
- Aluminum shingles: Aluminum shingles are available in styles that range from imitation cedar shakes to those with baked enamel colors such as red, green, black, and white. Aluminum shingles have an interlocking nailing flange on the sides so nails do not penetrate the shingle itself. They are light, weighing less than 50 pounds per square, compared to more than 300 pounds per square for average composition shingles.
- Copper shingles: These shingles are manufactured in a manner similar to the aluminum shingles, including the same type of interlocking nailing fins. Copper is heavier; approximately 100 pounds to the square.
- Slate: One of the oldest roofing materials around, slate is both beautiful and expensive. The best U.S. slate is made in Vermont and comes in a variety of colors. With proper maintenance, Vermont slate roofs last 100 years or more. Another key source of slate is Pennsylvania, but that slate is not as hard or as long lasting. Because of its weight, slate can be applied only to roofs built for that purpose. The material will crack easily if stepped on.
- Synthetic slate: Some synthetic slate is made from fiber cement and is not recommended by the manufacturers for application in freeze-thaw climates. The fibers in fiber cement roofing products are comprised of wood or cellulose and in some cases there have been allegations that the fibers can absorb water, which may lead to roof failure. Another synthetic slate is made from ceramic tile that is lighter than real slate and not as fragile yet is highly fire resistant.