[Er.Amit Mathur]

Roof system types
Roof systems and materials generally are divided into generic 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 3:12 (14 degrees). Steep slope roofing includes watershedding types of roof coverings installed on slopes exceeding 3:12 (14 degrees).

Low-slope roofing

There are five generic classifications of low slope roof membranes or systems. Click on a roof system for more information.
Built-up roof (BUR) membranes
Metal panel roof systems for low-slope applications
Polymer-modified bitumen sheet membranes
Single-ply membranes
Thermoplastic membranes (e.g., PVC, TPO)
Thermoset membranes (e.g., EPDM)
Spray polyurethane foam-based (SPF) roof systems

Steep-slope roofing

There are six generic classifications of steep slope roof coverings. Click on a roof covering type for more information.
Asphalt shingles
Clay tile and concrete tile
Metal roof systems for steep-slope applications
Slate
Wood shakes and wood shingles
Synthetic

For more details visit http://www.nrca.net/roofing/