What is a general term for sheet materials used in buildings that includes paper and felts?

The term "building paper" encompasses a variety of sheet materials used in construction, including paper and felts. It serves several functions, such as acting as a moisture barrier and providing additional protection for various structural elements. Building papers are designed to help mitigate water infiltration while allowing for some degree of vapor permeability, ensuring that moisture within the structure can escape.

In conjunction with roofing applications, building paper is often used beneath roofing materials to create a protective layer. While roofing felt, which is more specific, is commonly included in this category, building paper represents a broader classification that encompasses multiple types of materials used in maintaining moisture control across various building assemblies. This term is crucial for understanding the wide range of protective and insulating applications found in construction.