Roof pitch reference
16/12 roof pitch
A 16/12 roof rises 16 inches per 12 inches of run: 53.1°, a 133.3% grade, slope factor 1.6667. Each foot of run is 20 inches along the slope.
√(1 + (16 ÷ 12)²) = 1.6667 · between 15/12 (+60.1%) and 17/12 (+73.4%).
Roof area at 16/12
| Footprint | Roof at 16/12 | Squares |
|---|---|---|
| 1,200 sq ft | 2,000 sq ft | 20 |
| 1,600 sq ft | 2,667 sq ft | 26.7 |
| 2,000 sq ft | 3,333 sq ft | 33.3 |
| 2,600 sq ft | 4,333 sq ft | 43.3 |
Rafter length at 16/12
| Run (half span) | Rafter, no overhang |
|---|---|
| 10 ft | 16 ft 8 in (16.67 ft) |
| 12 ft | 20 ft 0 in (20 ft) |
| 14 ft | 23 ft 4 in (23.33 ft) |
| 16 ft | 26 ft 8 in (26.67 ft) |
Ice barrier on a 16/12 roof in Ohio and Michigan
Freeze-thaw winters in both states make eave protection one of the most important details on a 16/12 roof. Where the locally adopted code requires it, the model IRC (R905.1.2) extends ice barrier from the eave to at least 24 inches inside the exterior wall. On a 53.1° slope that distance grows by 66.7% when measured up the roof:
| Overhang | Horizontal | Up the 16/12 slope | 36-in courses |
|---|---|---|---|
| 12 in | 36 in | 60 in | 2 |
| 18 in | 42 in | 70 in | 3 |
| 24 in | 48 in | 80 in | 3 |
Courses assume a 3-inch lap (33 inches of coverage per 36-inch roll). Wall thickness adds a few inches. Check the product and your building department.
Shingles at 16/12
At 16/12 (53.1°, 133.3% grade) asphalt shingles install with standard underlayment under the IRC, plus ice barrier where the local code requires it.
Working on a 16/12 roof
A 53.1° slope behaves almost like a wall. A 16/12 roof needs full staging and fall protection, and shingle makers publish separate steep-slope application steps, such as extra nails and hand-sealing, for pitches like 16/12. OSHA treats anything steeper than 4/12 as a steep roof, so 16/12 falls under steep-roof fall protection rules.
Frequently asked questions
What angle is a 16/12 roof?
A 16/12 roof is about 53.1° from horizontal, a 133.3% grade. Over a 10-foot run it rises 13.33 feet.
How much bigger is a 16/12 roof than the footprint?
The slope factor is 1.6667, so the roof is 66.7% larger than the flat area under it. A 1,600 sq ft footprint has about 2,667 sq ft of roof (26.7 squares).
Can you put asphalt shingles on a 16/12 roof?
At 16/12 (53.1°, 133.3% grade) asphalt shingles install with standard underlayment under the IRC, plus ice barrier where the local code requires it.
How much ice barrier does a 16/12 roof need at the eaves?
With a 12-inch overhang, reaching 24 inches inside the wall takes about 60 inches measured up a 16/12 slope, which is 2 courses of 36-inch membrane with a 3-inch lap. Your local code decides whether ice barrier is required.