6/12 pitch at a glance
| Angle | 26.57° |
|---|---|
| Slope | 50.0% (6 in of rise per foot of run) |
| Pitch multiplier | 1.1180 |
| Hip and valley factor | 1.5000 per foot of common run |
| Type | Conventional |
A 6/12 roof gives the most common slope on American houses, steep enough to shed water well but still walkable. Its surface is 11.8% larger than the flat area it covers, so a 2,000 sq ft footprint needs about 2,236 sq ft of roofing.
Rafter length and ridge height by building width
On a simple gable at 6/12, a 24 ft wide building needs a 13 ft 5 in rafter measured from the outside of the wall to the center of the ridge, and a 32 ft wide one needs 17 ft 10 5/8 in. For 6/12, add your overhang and take off half the ridge board when you cut. Other spans are in the rafter length calculator.
| Building width | Run | Ridge rise | Rafter length |
|---|---|---|---|
| 20 ft | 10 ft | 5 ft 0 in | 11 ft 2 1/8 in |
| 24 ft | 12 ft | 6 ft 0 in | 13 ft 5 in |
| 28 ft | 14 ft | 7 ft 0 in | 15 ft 7 7/8 in |
| 32 ft | 16 ft | 8 ft 0 in | 17 ft 10 5/8 in |
| 36 ft | 18 ft | 9 ft 0 in | 20 ft 1 1/2 in |
Roof area, squares and shingle bundles
At 6/12 the multiplier is 1.118, so every 1,000 sq ft of footprint becomes 1,118 sq ft of roof. The order column for 6/12 adds 10% for waste and counts 3 bundles per square; include the eaves in your footprint or let the roofing squares calculator do it.
| Footprint | Roof area | Squares | Squares + 10% | Bundles |
|---|---|---|---|---|
| 1,200 sq ft | 1,342 sq ft | 13.4 | 14.8 | 45 |
| 1,600 sq ft | 1,789 sq ft | 17.9 | 19.7 | 60 |
| 2,000 sq ft | 2,236 sq ft | 22.4 | 24.6 | 74 |
| 2,400 sq ft | 2,683 sq ft | 26.8 | 29.5 | 89 |
What roofing can go on a 6/12 roof?
Allowed: Asphalt shingles; Clay and concrete tile; Metal shingles; Wood shingles; Slate.
At 6/12, 5 of the 5 roofing types in the code table are allowed outright. At 6/12 they follow the minimum slopes in the International Residential Code; local code and the maker's installation instructions can be stricter.
Can you walk on a 6/12 roof?
At 6/12: OSHA classes anything steeper than 4/12 as a steep roof, so professional crews need fall protection. It is walkable with care when dry, but frost, dew or loose granules make it slippery.
How to check that your roof is 6/12
Level a board against a rafter in the attic, mark 12 inches along it and measure straight down: 6 inches means 6/12. A phone level that reads 26.6 degrees says the same thing, and the roof pitch calculator converts either reading.
A worked example: a 28 by 40 ft house at 6/12
Half the width is 14 ft, so the ridge sits 7 ft 0 in above the top plate and each rafter is 15 ft 7 7/8 in long before overhang. The roof surface is 28 × 40 × 1.118 = 1,252 sq ft, which is 12.5 squares. On a 40 ft long 6/12 roof, rafters at 24 inches on center come to 21 per side.
Cutting rafters at 6/12
Each foot of horizontal run adds 13.42 inches of rafter length. On a speed square, put the pivot on the board edge and swing it until the 6 mark on the common scale lines up with the same edge; the pivot edge now scribes the plumb cut. On a miter saw, the plumb cut is set 26.6 degrees off square, and the horizontal seat cut is 63.4 degrees off square.
Attic headroom at 6/12
At least 5 ft of headroom for 8.0 ft of the 28 ft width, measured from the top plate. A usable attic room needs more than that at 6/12, because the floor joists and ceiling take up some of the height.
6/12 compared with the pitches next to it
The table uses the same 2,000 sq ft footprint for every row, so the last column shows the extra roofing a steeper pitch costs you.
| Pitch | Angle | Multiplier | Roof area | Difference |
|---|---|---|---|---|
| 4/12 | 18.4° | 1.054 | 2,108 sq ft | -128 sq ft |
| 5/12 | 22.6° | 1.083 | 2,167 sq ft | -69 sq ft |
| 6/12 | 26.6° | 1.118 | 2,236 sq ft | this pitch |
| 7/12 | 30.3° | 1.158 | 2,315 sq ft | +79 sq ft |
| 8/12 | 33.7° | 1.202 | 2,404 sq ft | +168 sq ft |
Other pitches: 5/12 pitch and 7/12 pitch, or the full roof pitch chart.
Frequently asked questions
What angle is a 6/12 roof pitch?
26.57 degrees. The slope is 50.0%.
What is the multiplier for a 6/12 pitch?
1.1180. Multiply the flat footprint by 1.118 to get the roof surface area.
Can you put shingles on a 6/12 roof?
Asphalt shingles can go on a 6/12 roof under the International Residential Code.
Is a 6/12 roof walkable?
OSHA classes anything steeper than 4/12 as a steep roof, so professional crews need fall protection.
Sources
- Cornell LII: 29 CFR 1926.500, definitions of low-slope and steep roofs
- LSU AgCenter: Code-Compliant Roofing Installations (PDF)