About the mono (lean-to) roof truss
A mono truss has a single sloping top chord, a bottom chord and a vertical heel at the high side. The whole span is one slope, so the rise is measured across the full width rather than half.
When to choose it
Use it for lean-to additions, carports, sheds and modern single-slope homes. Because there is no ridge, flashing against an existing wall is the main detail to plan.
How to use this calculator
- Enter the building span and the length along the ridge.
- Pick the pitch (or switch to an exact angle) and set the eave overhang.
- Choose spacing, material, snow and wind loads. Results update as you type.
Enter the full width as span. The calculator treats the run as the whole span for this roof type.
Practical tips
Pick a pitch that drains well for your roofing material. Metal panels can go as low as 1/12 to 2/12, while shingles need at least 2/12 with special underlayment and usually 4/12 or more.
Need a different figure? Try the span calculator, the cost calculator or compare options on the all truss types page.