What is the minimum slope for asphalt shingles?

• A. 1/4
• B. 1/3
• C. 1/6
• D. 2/3

Answer: (B)

Water drainage and the ability of asphalt shingles to seal properly depend on having enough incline. For standard asphalt shingles, the minimum slope is two inches of vertical rise for every twelve inches of horizontal run. Expressed as a ratio, that’s two-to-twelve, or one-sixth. This level of slope helps water shed quickly and gives the shingle tabs time to seal and resist wind uplift. If the roof is flatter than this, water can back up under the shingles, increasing the risk of leaks and potentially affecting warranty. In cases where the slope is lower, builders might use special underlayment or a different roofing material, but with typical asphalt shingles, two-to-twelve is considered the minimum.