What is the minimum recommended thickness for self-adhering polymer-modified bitumen membrane sheets as underlayment?

The minimum recommended thickness for self-adhering polymer-modified bitumen membrane sheets as underlayment is 40 mils. This specification is established to ensure adequate durability and performance of the underlayment in a roofing system. A thickness of 40 mils provides a balance between flexibility, tear resistance, and weather resistance, essential qualities for protecting the underlying structure from water infiltration.

Using membranes that meet or exceed this thickness standard helps to mitigate the risks associated with moisture penetration and other environmental factors, which can lead to significant damage over time. Therefore, choosing a thickness of 40 mils is in line with industry standards for maintaining the integrity and longevity of roofing installations.