9/12 Roof Pitch
A 9/12 roof (also written 9:12 or "9 on 12") rises 9 inches for every 12 inches of horizontal run: 36.87°, a 75.0% slope, and 25.0% more surface than its footprint.
| Measure | 9/12 value |
|---|---|
| Angle | 36.87° |
| Slope percent | 75.0% |
| Rise per foot of run | 9 in |
| Pitch multiplier (area factor) | 1.2500 |
| Hip/valley factor | 1.6008 |
| Common rafter length per foot of run | 15" |
| Plumb cut / seat cut | 36.9° / 53.1° |
Where you see a 9/12 roof
Typical uses: traditional and Victorian-style homes and attic bonus rooms. A 9/12 pitch is a 3-4-5 triangle in disguise: rise 9, run 12, slope 15. That makes the multiplier exactly 1.25, so the roof area is the footprint plus a quarter, and a rafter with a 12 ft run is exactly 15 ft long before the overhang.
Roof area at 9/12
9/12 formulas
Worked examples
9/12 rafter lengths and ridge heights
| Building span | Run | Rafter (no overhang) | Ridge rise |
|---|---|---|---|
| 16 ft | 8 ft | 10' 0" | 6' 0" |
| 20 ft | 10 ft | 12' 6" | 7' 6" |
| 24 ft | 12 ft | 15' 0" | 9' 0" |
| 28 ft | 14 ft | 17' 6" | 10' 6" |
| 32 ft | 16 ft | 20' 0" | 12' 0" |
| 36 ft | 18 ft | 22' 6" | 13' 6" |
Roof area by footprint at 9/12
| Footprint (incl. overhang) | Roof area | Squares |
|---|---|---|
| 1,000 sq ft | 1,250 sq ft | 12.5 |
| 1,500 sq ft | 1,875 sq ft | 18.8 |
| 2,000 sq ft | 2,500 sq ft | 25.0 |
| 2,500 sq ft | 3,125 sq ft | 31.3 |
| 3,000 sq ft | 3,750 sq ft | 37.5 |
Materials and walkability
- Shingles: Yes. 4/12 and steeper takes a standard shingle installation.
- Walkable? Not without equipment. Plan on roof jacks, harnesses and anchors.
- OSHA class: Steep roof (OSHA): OSHA treats anything steeper than 4/12 as a steep roof for fall-protection rules.
Roofing materials allowed on a 9/12 roof
| Roof covering | Code minimum | OK at 9/12? |
|---|---|---|
| Standing-seam metal panels | 0.25/12 (IRC R905.10.2) | Yes |
| Built-up, modified bitumen, single-ply membrane (TPO, EPDM, PVC) | 0.25/12 (IRC R905.9, R905.11, R905.12) | Yes |
| Lapped metal panels with lap sealant | 0.5/12 (IRC R905.10.2) | Yes |
| Mineral-surfaced roll roofing | 1/12 (IRC R905.5.2) | Yes |
| Asphalt shingles | 2/12 (IRC R905.2.2) | Yes |
| Clay and concrete tile | 2.5/12 (IRC R905.3.2) | Yes |
| Metal roof shingles | 3/12 (IRC R905.4.2) | Yes |
| Lapped metal panels, no sealant (exposed-fastener) | 3/12 (IRC R905.10.2) | Yes |
| Wood shingles and shakes | 3/12 (IRC R905.7, R905.8) | Yes |
| Slate | 4/12 (IRC R905.6.2) | Yes |
Sources
- International Code Council, International Residential Code (2021 and 2024), Section R905 minimum slopes, as summarized in IRC 2024 Chapter 9 (UpCodes) and the MyBuildingPermit residential re-roof checklist. Local amendments and manufacturer instructions can be stricter.
- OSHA, 29 CFR 1926.500(b): a low-slope roof is 4 in 12 or less; a steep roof is greater than 4 in 12. 1926.501(b)(13) requires fall protection for residential construction work 6 ft or more above a lower level.
← 8/12 pitch · 10/12 pitch → · All pitches in degrees
Frequently asked questions
How many degrees is a 9/12 roof pitch?
A 9/12 roof pitch is 36.87 degrees.
What is the multiplier for a 9/12 pitch?
The pitch multiplier for 9/12 is 1.2500. Multiply the footprint area or horizontal run by it to get the sloped area or rafter length.
Can you put shingles on a 9/12 roof?
Yes. 4/12 and steeper takes a standard shingle installation.
Is a 9/12 roof walkable?
Not without equipment. Plan on roof jacks, harnesses and anchors.
Last reviewed 2026-10-21. Results are estimates for planning; confirm quantities with your supplier and requirements with your local building code and the manufacturer's instructions.