What is a 4/12 roof pitch?
Short answer. A 4/12 roof pitch rises 4 inches for every 12 inches of horizontal run, an angle of about 18.4 degrees or a 33 percent grade. It is a low to moderate slope common on ranch homes, and it is the point where asphalt shingles can go on with a single layer of standard underlayment.
The numbers
- Angle: about 18.4 degrees
- Percent grade: 33.3 percent
- Pitch factor: 1.054, so a 2,000 square foot footprint has about 2,108 square feet of roof
- Rise over a 14 foot run: 56 inches, or 4 feet 8 inches
What roofing works on 4/12
- Asphalt shingles: yes. 4/12 is where the code's standard single layer underlayment applies; below it, double underlayment is required down to 2/12.
- Metal panels: yes, both exposed fastener and standing seam.
- Tile and slate: tile is allowed; slate needs at least 4/12, so 4/12 is its minimum.
Pros
- Walkable, so inspections and repairs cost less in time and safety gear.
- Less roof surface than steeper pitches over the same footprint.
- Wind sees a lower profile, especially on hip roofs.
Cons
- Water and debris move more slowly, so valleys, pine needles and leaf piles need attention under Georgia's trees.
- Less attic space for storage or ductwork.
- Wind driven rain can push farther up under shingles at low slopes, so good leak barrier in valleys and at walls matters.
Where you see it
Brick ranches across metro Atlanta, many porch and garage roofs, and some contemporary designs. See pine needles and leaves on the roof and ice and water shield in Georgia for details that matter more at this slope.