What is the minimum roof pitch?

Minimums by material

• Asphalt shingles: 2/12, and from 2/12 up to 4/12 the code calls for two layers of underlayment (or the manufacturer's low-slope method).
• Lapped, exposed fastener metal panels without lap sealant: 3/12.
• Lapped metal panels with lap sealant: one half inch per foot.
• Standing seam metal: one quarter inch per foot.
• Clay and concrete tile: 2.5/12 with double underlayment, standard underlayment from 4/12.
• Slate: 4/12.
• Wood shingles: 3/12.
• Membranes such as modified bitumen, TPO and EPDM: generally a quarter inch per foot, so they are not truly flat.

Manufacturers can be stricter

Code is the legal floor. Manufacturers' installation instructions, which code also requires you to follow, may demand more, such as self-adhered underlayment on the whole low-slope area. Some metal panel makers set higher minimums than code for particular profiles. A roof installed below the manufacturer's minimum can lose its warranty.

Minimum is not the same as ideal

At 2/12 or 3/12, shingles shed water slowly, and wind-driven rain or a clogged gutter can push water uphill under them. That is why low porch roofs and additions are such common leak spots on Georgia homes. If your porch sits right at the minimum, the underlayment and the flashing where it meets the wall matter more than the shingle brand.

See our underlayment comparison and ice and water shield in Georgia for the materials that make low slopes work.