On roof slopes greater than 4/12, what is the minimum overlap required for underlayment courses horizontally?

The minimum overlap required for underlayment courses horizontally on roof slopes greater than 4/12 is 2 inches. This requirement is in place to ensure proper water shedding and to prevent leaks, especially in areas that are subjected to high moisture or rain. When the roof slope exceeds this gradient, the risk of water infiltration increases, making adequate overlap crucial for maintaining the integrity of the roofing system.

A 2-inch overlap allows sufficient material to overlap the course below, which helps to direct water off the roof and minimizes the potential for it to seep through seams. This standard is established by roofing guidelines to ensure durability and protection against weather-related issues.

In contrast, smaller overlaps might not provide enough coverage, increasing the likelihood of water ingress, while larger overlaps might be unnecessary and could complicate the installation without adding significant benefits. Thus, the specified 2-inch minimum is a balance of effectiveness and practicality in roofing applications.