12 Foot Gambrel Roof Truss Calculator
A 12 ft gambrel is the sweet spot for sheds, garden buildings, and small chicken coops. The short span keeps lumber to 2×6 SPF #2 and the entire roof can be framed with simple bird's-mouth cuts and a single gusset at the knuckle, no engineered trusses required.
Pre-Calculated Results for 12 ft Span
| Sweep Angle | Lower Rafter | Upper Rafter | Total Height | Roof Area (20 ft L) |
|---|---|---|---|---|
| 45° | 8.49 | 0.00 | 6.00 | 417 |
| 60° | 6.00 | 3.11 | 6.00 | 445 |
| 67.5° | 4.59 | 4.59 | 6.00 | 448 |
Why 12 ft Works for Sheds
At 12 ft wide the loft floor is about 6 ft across at the knuckle, enough for hay, seasonal storage, or a small workshop platform. Total height tops out at 6 ft above the wall plate, which keeps the build under most accessory-structure height limits without a permit in many US jurisdictions.
Material Cost Snapshot
A 12 ft × 16 ft gambrel shed needs roughly 24 rafters, 20 sheets of 7/16 in OSB, and 4 squares of asphalt shingles. At 2024 lumber prices that is around US$1,200–1,600 in materials before fasteners, felt, and trim.
Typical Applications for a 12 ft Gambrel
A 12 ft wide gambrel is sized for shed, garden building, small chicken coop. With a 60° sweep angle the lower rafters land at 6.00 ft and upper rafters at 3.11 ft, both within the capacity of 2×6 SPF #2 for typical residential loads at 16 in on center rafter spacing.
Total roof height at the standard 60° sweep is 6.0 ft above the wall plate. Loft floor area inside the knuckle is approximately 6.0 ft wide and runs the full length of the building, usable for storage, a sleeping loft, or a workshop above the main floor.