40 Foot Gambrel Roof Truss Calculator
At 40 ft wide a gambrel is firmly in the agricultural and equestrian category. Stick-framed rafters become impractical; engineered trusses with steel gusset plates or LVL chords are the standard. Total height tops 20 ft, so check local zoning before finalizing wall heights.
Pre-Calculated Results for 40 ft Span
| Sweep Angle | Lower Rafter | Upper Rafter | Total Height | Roof Area (20 ft L) |
|---|---|---|---|---|
| 45° | 28.28 | 0.00 | 20.00 | 1289 |
| 60° | 20.00 | 10.35 | 20.00 | 1380 |
| 67.5° | 15.31 | 15.31 | 20.00 | 1391 |
Truss Engineering at 40 ft
Pre-engineered 40 ft gambrel trusses ship with 2×10 or 2×12 chords, internal webbing, and 18-gauge steel gusset plates. Truss spacing of 2 ft or 4 ft on center is typical, with purlins added between trusses on wider spacing.
Hay Storage and Riding Arenas
A 40×60 gambrel barn provides roughly 1,200 ft² of loft hay storage, enough for 80–100 round bales depending on bale size. 40×80 covered riding arenas use the wide center aisle, with stalls and tack rooms tucked into the lower-pitch eave area.
Typical Applications for a 40 ft Gambrel
A 40 ft wide gambrel is sized for large agricultural barn, riding arena, equipment storage. With a 60° sweep angle the lower rafters land at 20.00 ft and upper rafters at 10.35 ft, both within the capacity of 2×12 SPF #2 or LVL for typical residential loads at 16 in on center rafter spacing.
Total roof height at the standard 60° sweep is 20.0 ft above the wall plate. Loft floor area inside the knuckle is approximately 20.0 ft wide and runs the full length of the building, usable for storage, a sleeping loft, or a workshop above the main floor.