What is the best roof pitch for snow load?

How pitch changes snow load

Structural engineers start with a ground snow load for the location, then adjust it for exposure, heating and slope. On a typical shingle roof, the slope adjustment does little until the roof reaches about 30 degrees, roughly a 7:12 pitch, and then reduces the load as the roof gets steeper. Slippery surfaces like metal let snow slide at much lower slopes, which is why metal roofs shed snow so readily.

Steep is not always better

• Sliding snow. Snow that slides can tear off gutters, damage lower roofs and land on walkways. Metal roofs often need snow guards above doors.
• Drifts. Valleys, dormers and roofs below taller walls collect drifts regardless of pitch.
• Cost and style. Steeper roofs need more material and slower, safer installation.

Georgia reality

Georgia's design ground snow loads are low compared with northern states, with the North Georgia mountains the most exposed. Your local building department sets the design value. The bigger winter risks here are freezing rain, which coats limbs until they break onto roofs, and occasional ice dams where snow lingers on a shaded eave. Keeping trees trimmed back matters more than pitch for most Georgia homes; see trees and your roof. If you are considering metal for a mountain home, read metal roofing in Georgia.