Asphalt shingles can only be used on roof slopes of what ratio or greater?

Asphalt shingles are typically recommended for roof slopes of 4:12 or steeper to ensure proper drainage and to minimize the risk of water infiltration. Roofs with a slope of 4:12 mean that for every 12 horizontal inches, the roof rises 4 vertical inches. At this slope, the shingles are able to shed water effectively, reducing the chances of leaks and prolonging the lifespan of the roofing material.

Using asphalt shingles on roof slopes below this ratio, such as 3:12 or 2:12, can lead to water accumulation and increase the likelihood of moisture issues, which is why guidelines recommend the minimum slope of 4:12. By adhering to this standard, contractors can ensure that their roofing installations are compliant with building codes and best practices for durability and weather resistance.