ARCA divides roof systems and materials into two classifications: low slope and steep slope. Low slope roofing includes water impermeable, or weatherproof, types of roof membranes installed on slopes less than or equal to 2:12. Steep slope roofing includes watershedding types of roof coverings installed on slopes exceeding 4:12.

Low-Slope roofing

There are three classifications of low slope roof membranes or systems.