About the gable roof truss
A gable truss has two equal sloping top chords that meet at a central ridge, with a flat bottom chord and triangulated web members between them. It is the most common residential roof shape because it is simple to build and easy to shed water and snow.
When to choose it
Choose a gable truss for houses, garages, porches and extensions where you want a straightforward roof at a reasonable cost. Pitches from 4/12 to 8/12 suit most climates.
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.
The default example is a 30 ft by 40 ft building at 6/12 pitch with a 12 in overhang, which returns about 21 trusses at 24 in spacing.
Practical tips
Keep spacing at 24 inches on center unless snow load or lumber size demands tighter spacing. Remember that the overhang adds length to every top chord, so order lumber with the tail included. Plan gable-end framing and bracing early.
Need a different figure? Try the span calculator, the cost calculator or compare options on the all truss types page.