What does a roof pitch slope chart tell you about roofing materials?
Short answer. A roof pitch slope chart pairs each pitch with its slope factor and, on the useful versions, the roofing materials allowed at that slope. Asphalt shingles need at least 2/12 (with double underlayment up to 4/12), lapped metal panels without sealant need 3/12, clay and concrete tile need 2.5/12, and slate needs 4/12.
Slope bands and what they allow
- Under 2/12: low slope territory. Shingles are not allowed. Membrane roofs and standing seam metal are designed for these slopes, down to about 1/4 inch per foot.
- 2/12 to under 4/12 (slope factor 1.014 to 1.054): shingles allowed with a double layer of underlayment or a manufacturer approved low slope method. Lapped metal panels need applied lap sealant below 3/12. Tile is allowed from 2.5/12 with extra underlayment.
- 4/12 to 9/12 (slope factor 1.054 to 1.250): the conventional range. Standard underlayment, standard nailing, and every common residential material works, including slate from 4/12.
- Over 9/12 (slope factor 1.30 and up): steep. Materials work fine, but crews need roof jacks and harnesses, and above about 20/12 shingles need special fastening.
Slope factors
The slope factor converts flat area to real roof area: 5/12 is 1.083, 6/12 is 1.118, 8/12 is 1.202, 10/12 is 1.302 and 12/12 is 1.414. A 6/12 roof has about 12 percent more surface than its footprint.
Code minimums are the floor, not the target
These minimums come from the International Residential Code, which Georgia adopted in its 2024 edition with state amendments effective January 1, 2026. Manufacturers can set stricter rules, and their installation instructions control the warranty. A shingle roof at 3/12 is legal with the right underlayment, but water moves slowly on it, so details at valleys and walls matter more.
For material choices on your slope, see metal roofing in Georgia and synthetic underlayment vs felt.