11/12 Roof Pitch
A 11/12 roof (also written 11:12 or "11 on 12") rises 11 inches for every 12 inches of horizontal run: 42.51°, a 91.7% slope, and 35.7% more surface than its footprint.
| Measure | 11/12 value |
|---|---|
| Angle | 42.51° |
| Slope percent | 91.7% |
| Rise per foot of run | 11 in |
| Pitch multiplier (area factor) | 1.3566 |
| Hip/valley factor | 1.6853 |
| Common rafter length per foot of run | 16-1/4" |
| Plumb cut / seat cut | 42.5° / 47.5° |
Where you see a 11/12 roof
Typical uses: Tudor and Victorian homes, steep gables and dormers. An 11/12 roof (42.5 degrees) is just shy of 45. It is uncommon on main roofs but shows up on decorative gables and dormers. Material quantities climb fast: the roof has about 36% more surface than its footprint.
Roof area at 11/12
11/12 formulas
Worked examples
11/12 rafter lengths and ridge heights
| Building span | Run | Rafter (no overhang) | Ridge rise |
|---|---|---|---|
| 16 ft | 8 ft | 10' 10-1/4" | 7' 4" |
| 20 ft | 10 ft | 13' 6-13/16" | 9' 2" |
| 24 ft | 12 ft | 16' 3-3/8" | 11' 0" |
| 28 ft | 14 ft | 18' 11-7/8" | 12' 10" |
| 32 ft | 16 ft | 21' 8-7/16" | 14' 8" |
| 36 ft | 18 ft | 24' 5" | 16' 6" |
Roof area by footprint at 11/12
| Footprint (incl. overhang) | Roof area | Squares |
|---|---|---|
| 1,000 sq ft | 1,357 sq ft | 13.6 |
| 1,500 sq ft | 2,035 sq ft | 20.3 |
| 2,000 sq ft | 2,713 sq ft | 27.1 |
| 2,500 sq ft | 3,391 sq ft | 33.9 |
| 3,000 sq ft | 4,070 sq ft | 40.7 |
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 11/12 roof
| Roof covering | Code minimum | OK at 11/12? |
|---|---|---|
| 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.
← 10/12 pitch · 12/12 pitch → · All pitches in degrees
Frequently asked questions
How many degrees is a 11/12 roof pitch?
A 11/12 roof pitch is 42.51 degrees.
What is the multiplier for a 11/12 pitch?
The pitch multiplier for 11/12 is 1.3566. Multiply the footprint area or horizontal run by it to get the sloped area or rafter length.
Can you put shingles on a 11/12 roof?
Yes. 4/12 and steeper takes a standard shingle installation.
Is a 11/12 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.