What type of underlayment is required for roof slopes of 3:12 and over in clay and concrete roof tiling?

For roof slopes of 3:12 and over when using clay and concrete roof tiles, both Type I underlayment and self-adhering polymer-modified sheet underlayment are required to ensure proper waterproofing and protection against leaks.

Type I underlayment is often used for its durability and moisture-resistant properties. It provides a reliable barrier against water infiltration, which is particularly important in areas that might experience heavy rainfall. The self-adhering polymer-modified sheet underlayment adds an additional layer of protection. It adheres directly to the roof deck and provides enhanced waterproof capabilities, especially in vulnerable areas such as eaves and valleys where water can tend to accumulate.

Using both types of underlayment together creates a comprehensive waterproofing system, which is essential for maintaining the integrity of the roofing system against the elements, particularly given the performance characteristics of clay and concrete tiles. This dual approach ensures that the roofing assembly is resilient and less prone to damage from moisture, contributing to the longevity of the roof.