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How Steep Does A Roof Have To Be To Put Asphalt Shingles On?

The most common roof in use today is the asphalt shingle roof. It is typically seen on residential buildings, which usually have a moderate pitch of about 4:12. Flat roofs are usually composed of tar and gravel, EPDM membrane, or modified bitumen. These roofs will have pitches in the range of 0 to 2:12. Since asphalt shingling is in high demand, what pitch is required of a roof to qualify for asphalt shingles, and why?

Typically, a roof must have a pitch of at least 2:12 to qualify for asphalt shingles. This means that for every 2 inches that a roof rises, it will have 12 inches of “run.” Why is this required?

The simple answer is gravity. Roofs with steeper pitches will drain water much faster and easier as they approach a vertical pitch. As the roof flattens out, water will have a tendency to drain more slowly. Asphalt shingles create crevices and bumps that water must pass over to drain. A roof with a flat pitch may not be able to drain all of this water, which can lead to roof leaks, dry rot, and bacteria buildup.

If you have any further questions related to flat roofs or asphalt shingling, give us a call at (918) 558-ROOF (7663).