What is the minimum exposure for the second and subsequent strips of double underlayment?

The minimum exposure for the second and subsequent strips of double underlayment is 17 inches. This measurement is important because it helps ensure proper water shedding and protects the roof structure beneath the shingles. Double underlayment is typically used in roofing to provide an extra layer of protection against water infiltration, especially in areas prone to heavy rain or snow. By maintaining a minimum exposure of 17 inches for subsequent strips, it ensures that overlaps are sufficient to mitigate potential leaks and that structural integrity is maintained, with enough coverage to direct water away effectively. This standard helps prevent moisture issues that could lead to rot or deterioration of the roof deck over time.