What a 19/12 pitch means
A 19/12 roof rises 19 inches for every 12 inches it runs horizontally, which is an angle of 57.72° from level and a 158.3% slope. It is a steep roof, too steep to walk safely without roof jacks or a harness.
Roofing for a 19/12 roof
Suits shingles, metal, slate and tile. Steep enough that roofers need roof jacks or harnesses, which adds to labour cost.
Rise and rafter length at 19/12
For a gable roof, the run is half the building width. Rafter lengths are before the ridge deduction and overhang.
| Run | Building width | Rise | Rafter length |
|---|---|---|---|
| 4 ft | 8 ft | 6' 4" | 7' 5 7/8" |
| 6 ft | 12 ft | 9' 6" | 11' 2 13/16" |
| 8 ft | 16 ft | 12' 8" | 14' 11 3/4" |
| 10 ft | 20 ft | 15' 10" | 18' 8 3/4" |
| 12 ft | 24 ft | 19' | 22' 5 11/16" |
| 14 ft | 28 ft | 22' 2" | 26' 2 5/8" |
| 16 ft | 32 ft | 25' 4" | 29' 11 9/16" |
| 20 ft | 40 ft | 31' 8" | 37' 5 7/16" |
Roof area at 19/12
Multiply the building footprint (including the overhangs) by 1.873 to get the roof surface. A 30 × 40 ft footprint has 2247 sq ft of roof at 19/12 — about 71 sheets of 4 × 8 sheathing before waste.