What is required between courses of low slope asphalt shingles?

Low slope asphalt shingles require an additional layer of underlayment or a waterproofing membrane between courses to ensure adequate protection against water infiltration. This is particularly important in low slope applications, as gravity does not effectively shed water as it does on steeper roofs. The underlayment acts as a secondary barrier, preventing moisture from penetrating through the shingles, which can lead to leaks and damage to the underlying structure.

The use of underlayment or a waterproofing membrane is critical in areas where there is a risk of water pooling or where the slope is insufficient to allow for proper drainage. It provides an added layer of security and helps prolong the life of the roofing system.

Other options, like sealant or tar paper, might have their uses in specific applications, but they do not provide the same level of comprehensive protection against moisture as underlayment or a waterproofing membrane. Insulation, while important for temperature regulation, does not serve a purpose in preventing water ingress and is not required between the courses of shingles.