Steep pitches compared
The extra area column uses a 2,000 sq ft footprint compared with 6/12. Ridge height is for a 28 ft wide house, measured above the top plate.
| Pitch | Angle | Multiplier | Extra area vs 6/12 | Ridge height (28 ft wide) |
|---|---|---|---|---|
| 9/12 | 36.9° | 1.250 | +264 sq ft | 10 ft 6 in |
| 10/12 | 39.8° | 1.302 | +367 sq ft | 11 ft 8 in |
| 12/12 | 45.0° | 1.414 | +592 sq ft | 14 ft 0 in |
| 14/12 | 49.4° | 1.537 | +837 sq ft | 16 ft 4 in |
| 16/12 | 53.1° | 1.667 | +1,097 sq ft | 18 ft 8 in |
| 18/12 | 56.3° | 1.803 | +1,369 sq ft | 21 ft 0 in |
The multiplier at 12/12 is 1.414, so the roof has 26% more area than a 6/12 roof on the same house. At 18/12 it is 61% more.
Safety and labor
- OSHA. Anything over 4/12 is a steep roof for fall protection, and crews need guardrails, safety nets or personal fall arrest.
- Cost. Roofers often charge a steep-slope rate from about 7/12 or 8/12, because materials must be handled on the slope.
- Do not climb it yourself. Measure from the attic or the gable end. See how to measure roof pitch.
What works on a steep roof
All common steep-slope roofing is allowed: asphalt shingles, metal, tile, slate and wood shingles. Slate needs a minimum of 4/12 and works well here. Fastening instructions may change at very steep slopes, so read the manufacturer's data for the exact pitch.
Why choose steep
- Snow and water run off quickly.
- More attic volume, and with enough headroom a usable room.
- Traditional appearance, such as Tudor, Victorian and Cape Cod styles.
The trade-offs
More roof to cover, longer rafters, taller walls on the gable ends, and a harder installation. For the rafter length at a given pitch, use the rafter length calculator. To size the covering, use the roof area calculator. For the middle of the range, see standard roof pitch.
Frequently asked questions
What is considered a steep roof pitch?
OSHA says over 4/12 for fall protection. Roofers usually mean 9/12 or steeper when they quote a steep-slope rate.
How many degrees is a 12/12 roof?
45 degrees.
Can you walk on a 10/12 roof?
Not safely without equipment. At 10/12 the angle is 39.8 degrees and crews work from roof jacks or tied off.
Sources
- Cornell LII: 29 CFR 1926.500, definitions of low-slope and steep roofs
- LSU AgCenter: Code-Compliant Roofing Installations (PDF)