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.
There are three classifications of low slope roof membranes or systems.
- Built-up roof (BUR) membranes
- S.B.S-modified bitumen membranes
- Single-ply membranes
There are four classifications of steep slope roof coverings.