3/12 roof pitch
A 3/12 roof rises 3 inches for every 12 inches it runs: an angle of 14.0°, and a low-slope roof. You see it on ranch houses, porches, sheds and low additions.
- Angle
- 14.04°
- Slope
- 25.0%
- Area multiplier
- ×1.031
- Rafter per foot of run
- 12.37"
What 3/12 means for your roof
Size. A roof is bigger than the ground it covers. At 3/12 every square foot of footprint carries 1.031 sq ft of roof, so a 2,000 sq ft house has about 2,062 sq ft (20.6 squares) of roofing before overhangs and waste. A quote measured on the footprint alone under-buys every shingle and every hour of labour by 3.1%.
Working on it. Walkable. Shingles go on with doubled underlayment, and debris tends to sit, so gutters and valleys need more attention than on steeper roofs.
Cost. Replacing architectural shingles on that 2,000 sq ft house, old layer torn off, comes to about $11,500–$13,200 at US-average roofer wages. That figure follows the roof's area only: most roofers price standard labour at this pitch, with no steep-roof charge. Price your own roof from satellite.
Roofing materials at 3/12
Minimum slopes in the International Residential Code (2021). Cities adopt it with changes, and a manufacturer's instructions can be stricter, so check locally before you buy.
- Asphalt shingles — allowed (minimum 2/12, IRC R905.2.2); below 4/12 they need two layers of underlayment
- Clay or concrete tile — allowed (minimum 2½/12, IRC R905.3.2); below 4/12 they need two layers of underlayment
- Metal shingles — allowed (minimum 3/12, IRC R905.4.2)
- Slate — not allowed (minimum 4/12, IRC R905.6.2)
- Standing-seam metal panels — allowed (minimum ¼/12, IRC R905.10.2)
3/12 pitch questions
What is a 3/12 roof pitch in degrees?
14.04 degrees. The angle is arctan(3 ÷ 12). As a percent slope it is 25.0%.
How much bigger is a 3/12 roof than the house's footprint?
Multiply the footprint by 1.031. A 2,000 sq ft footprint has about 2,062 sq ft of roof at 3/12, before overhangs and waste.
Can you put shingles on a 3/12 roof?
Yes, but the model building code (IRC R905.2.2) requires two layers of underlayment on shingle roofs below 4/12, and slow drainage makes leaks at seams more likely.
Is a 3/12 roof walkable?
Walkable. Shingles go on with doubled underlayment, and debris tends to sit, so gutters and valleys need more attention than on steeper roofs.
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