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.

• Built-up roof (BUR) membranes
• S.B.S-modified bitumen membranes
• Single-ply membranes
  • Thermoset membranes (e.g., EPDM)
  • Thermoplastic membranes (e.g., PVC, TPO)

Steep-Slope Roofing

There are four classifications of steep slope roof coverings.

• Asphalt shingles
• Slate Tile
• Cedar shakes and shingles
• Architectural Standing Seam Metal