'Everything You Always Wanted To Know About Roofing, But Were Afraid To Ask!
Your roof style dictates to a large degree what roofing material you should select. Flat or nearly flat roofs must be covered with built-up roofs such as tar and gravel or more modern counterparts to keep water out. For roofs, with a slight to no pitch i.e. tar and gravel, bitumen, roll roofing, or even metal sheet roofs work well. (See how to measure your roof's pitch and square footage below for an explanation of pitch.) To be shingled or tiled, a roof must have a greater slope, so rain can't blow under the shingle.
Flat roofs are common in areas with little rainfall or snow and on industrial buildings with wide roof spans.
TAR AND GRAVEL ROOF:
Also known as the built-up roof, it is used primarily on flatter roofs. Even flat roofs are sloped somewhat to prevent water from collecting. Tar and gravel roofs are constructed from alternating layers of heavy roofing felt and hot asphalt or tar and finished with a protective mineral coat, such as gravel or mica. The roofs are rated by how many layers are installed, usually from three to five.
MODIFIED BITUMEN ROOFING:
This type of roofing combines many of the features in the standard tar and gravel roof with the addition of layers of polyester or fiberglass impregnated with bitumen, a derivative of tar or asphalt. The roofing is put down in multiple plies, or layers, and gains significant strength and resistance to weathering by adding polyester membranes. Other bitumen modifier agents that enhance asphalt's qualities include atactic polypropylene (APP) and styrene butadiene styrene (SBS).
EPDM RUBBER ROOFING:
Originally for commercial use, it is gaining popularity as a long-lasting roofing material for flat and low-slope residential roofs. The initials stand for ethylene propylene diene monomer, which is used to create the single-ply rubberized roof. It is UV resistant and does not require a mineral coating when completed, thus making it lighter than tar and gravel. It comes in two thickness, 45 millimeters and 60 millimeters. A common underlayment for this roof is rigid insulation on the roof deck.
Commonly used for sheds or inexpensive roofs, it is a low-cost roofing material with a short life. It is generically known as 90-pound felt because one roll, which covers 100 square feet, weighs 90 pounds. Although it is mineral-surfaced and underlaymentmade from the same material as asphalt shingles, it has a life expectancy of ten years or less because it is only one layer deep. Shingles last longer because the manner in which they are overlapped makes them three layers deep.
Technically, roofing felt is roll roofing, but it is never used by itself as a roofing material. Although water resistant, it is thin and tears easily. Made of asphalt-impregnated felt, it is used as an underlayment between the roof deck and the roofing material. It is sold as 15 or 30-pound felt, a figure that represents the weight of 'one square' (or 100 square feet) of the material. It is sold in rolls of 36" wide, which can cover either two or four 'squares'. When using roofing felt, it is important to roll it out flat and smooth. Any wrinkles and bumps may show through after asphalt shingles are installed.
Metal roofs have been around for years, particularly the old corrugated ones, which were commonly used on farm buildings around the country. More recently, the standing seam metal roofs in a variety of colors can be seen on even high-end houses. Metal roof panels also can be used on nearly flat roofs. One drawback is that metal roofs conduct heat so effectively, they radiate into the areas below unless well insulated.
Pitched or sloped roofs range from moderately sloped to greater sloped and are commonly seen on A-frame roofs. Even steeper are mansard roofs and parts of gambrel roofs such as on barns.
ROOFING MATERIALS IDEALLY SUITED FOR FOR PITCHED ROOFS INCLUDE THE FOLLOWING:
COMPOSITION SHINGLES: Generically called asphalt shingles, these are used in 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 fiber. 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.
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 to up to 40 years. As with composition shingles, the manufacturer's warranty generally applies only if one of their certified roofers installs the material.
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).
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 building codes if considering such a roof.
The familiar Spanish or mission tiles are commonly made from clay or concrete. Tile shapes include the half-barrel, S-shaped, 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 x 6 boards nailed to a 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 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.
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.
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.
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.