30 Foot Gambrel Roof Truss Calculator
A 30 ft gambrel is barn territory. Lower rafters cross the 2×8 threshold at this span; most jurisdictions require 2×10 SPF or LVL rafters once snow load exceeds 30 psf. Loft floor is wide enough for hay storage, equipment, or a finished second floor.
Pre-Calculated Results for 30 ft Span
| Sweep Angle | Lower Rafter | Upper Rafter | Total Height | Roof Area (20 ft L) |
|---|---|---|---|---|
| 45° | 21.21 | 0.00 | 15.00 | 977 |
| 60° | 15.00 | 7.76 | 15.00 | 1046 |
| 67.5° | 11.48 | 11.48 | 15.00 | 1054 |
Engineered Truss vs Stick Frame
At 30 ft most builders switch from stick-framed rafters to factory-built gambrel trusses on 2 ft centers. Trusses arrive with engineered gusset plates and a stamped load calc: faster to install, fewer cuts, and easier to permit in snow country.
Common 30 ft Builds
30×40 horse barns with a 10-stall center aisle, 30×30 three-car residential garages, and 30×60 agricultural storage buildings all use this span. Plan for a 12 ft wide center aisle if you want a tractor or skid steer to pass through the loft door at the gable end.
Typical Applications for a 30 ft Gambrel
A 30 ft wide gambrel is sized for agricultural barn, three-car garage, workshop. With a 60° sweep angle the lower rafters land at 15.00 ft and upper rafters at 7.76 ft, both within the capacity of 2×10 SPF #2 for typical residential loads at 16 in on center rafter spacing.
Total roof height at the standard 60° sweep is 15.0 ft above the wall plate. Loft floor area inside the knuckle is approximately 15.0 ft wide and runs the full length of the building, usable for storage, a sleeping loft, or a workshop above the main floor.