What is the minimum overlap required for underlayment courses on roof slopes greater than 4/12?

For roof slopes greater than 4/12, the minimum overlap required for underlayment courses is 2 inches. This overlap is essential for preventing water infiltration and ensuring that the roofing system performs effectively.

When the underlayment is installed with the specified overlap, it helps create a secondary barrier against moisture. This is particularly important on steeper roof slopes, where water may run off more quickly, but wind-driven rain can still be a concern. The 2-inch overlap provides a sufficient water-shedding surface and minimizes the risk of water intrusion at the seams where the underlayment courses meet.

Using too little overlap, such as 1 inch, could increase the likelihood of moisture infiltration, which ultimately can lead to roofing failures or leaks. Therefore, adhering to the 2-inch minimum overlap standard is crucial for the integrity and longevity of the roofing system.