What slope range indicates the use of one ply for asphalt shingles?

The correct answer highlights that a slope range of 2:12 to 4:12 is specified for the use of one ply for asphalt shingles. This slope is considered suitable for a single layer of shingles because it provides enough angle to ensure proper drainage while minimizing the risk of water pooling, which can lead to leaks and damage.

In roofing terminology, the ratio represents the vertical rise over the horizontal run. A slope of 2:12 means that for every 12 inches of horizontal distance, there is a rise of 2 inches, while a 4:12 slope rises 4 inches over the same distance. The range specified offers a balance that allows for adequate water runoff, making a single ply sufficient for effective waterproofing in these slope conditions.

This range is critical because roofs with steeper slopes (above 4:12) can typically handle heavier materials or additional layers due to better drainage. Conversely, slopes that are too low (less than 2:12) often require additional protection or different roofing materials altogether. Therefore, utilizing one ply in the 2:12 to 4:12 range is standard practice to ensure durability and effectiveness in residential construction under that slope condition.