One layer of thin, asphalt shingles can add more than a ton of weight to your roof. Thicker asphalt shingles can increase the load by about 50 percent. Nonetheless, standard asphalt shingles are among the most lightweight roofing materials available to homeowners.
Asphalt materials cover the roofs of more U.S. homes than any other roofing material. Four out of five homes have asphalt shingles, according to the Asphalt Roofing Manufacturers Association. The association indicates that manufacturers make enough asphalt roofing each year to cover more than five million homes. Asphalt makes shingles waterproof, but it also holds granules in place that increase the strength and durability of shingles. Standard shingles usually have a single layer of granulated asphalt attached to a fiberglass backing, and they weigh less than slate, clay tiles and thicker asphalt roofing materials.
Standard asphalt shingles generally weigh about 190 pounds per 100 square feet, based on information from U.S. Inspect, a property inspection company. The weight of asphalt is especially important if you want to install a new layer of asphalt roofing over an existing layer. A roof measuring 1,600 square feet that has two layers of standard asphalt shingles on it is holding about 6,000 pounds of shingles. Therefore, it's important to have a professional contractor determine if the underlying structure of your roof can bear the load of two layers of shingles.
Dimensional, or architectural, asphalt shingles are designed to mimic more expensive roofing materials, such as clay tiles or wood shakes. Dimensional shingles are thicker than standard asphalt shingles so that they resemble the natural materials they represent. U.S. Inspect indicates that dimensional shingles can be 50 percent heavier than standard asphalt roofing. Therefore, they could weigh about 285 pounds per 100 square feet. Heavier shingles reduce the chance the underlayment will wrinkle, according to the National Roofing Contractors Association. Underlayments protect the roof deck from moisture beneath shingles.
Builders install roof framing at about 20 pounds per square feet to keep a roof from collapsing under the weight of asphalt materials, according to U.S. Inspect. Homeowners who live in areas known for heavy snowfall should consider keeping the weight of roofing materials as low as possible, since snow adds more weight for the framing to bear.
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