Mono Roof Truss Calculator
A mono, or monopitch, roof truss uses a single sloped plane instead of two meeting at a ridge — the shape behind lean-to additions, modern single-slope homes, and many flat and shed roof designs. This calculator sizes mono roof trusses from span, pitch, and spacing.
Size Your Mono / Lean-To Roof Truss
Enter your building specifications below. Results and the roof diagram update live as you type.
Live Roof Diagram
Results
Estimate Your Project Budget
Automatically calculated from your inputs above in the calculator.
Estimates only. Actual costs vary by region, supplier, and site conditions.
Mono, Lean-To, Single-Slope & Flat Roof Trusses
A mono truss is essentially half of a gable truss — one sloped top chord running from a high wall to a low wall, with a single water-shedding direction. It is the standard choice for lean-to additions, carports, and modern single-slope architecture.
Low-slope and flat roof trusses (roughly 0.5/12 to 3/12) use the same mono profile but with a much shallower pitch, relying on membrane roofing and positive drainage rather than a steep slope to shed water.
Because a mono roof has no ridge to split the load, the high wall must be engineered to carry the full uplift and gravity load transferred from the single slope — confirm wall framing and connections match your truss manufacturer's specifications.
Frequently Asked Questions
Flat roof truss calculator
Use the Mono / Flat roof truss calculator for low-slope and flat designs.
Single slope roof truss calculator
Covered by the Mono / Lean-to calculator.
Shed roof truss design calculator
Use the Mono / Lean-to and Garage/Barn calculators for shed and outbuilding trusses.