At what slope are asphalt shingles NOT allowed to be installed?

Asphalt shingles are not permitted to be installed on roofs with a slope of less than 2 inches in 12 inches (2:12). This is primarily because lower slopes do not allow for adequate drainage, which increases the risk of water pooling and can lead to leaks over time.

When asphalt shingles are installed on roofs with a pitch that is too low, they may not shed water effectively, especially during heavy rains or snowmelt. The manufacturers of these shingles often specify a minimum slope requirement to ensure their product performs as intended and to maintain warranty coverage. Using asphalt shingles on slopes below the 2:12 threshold could lead to increased vulnerability to various weather conditions, resulting in premature deterioration and potential failure of the roofing system. Thus, maintaining the minimum slope guideline is crucial for the longevity and functionality of asphalt shingle roofs.