Roofing · Common-rafter geometry
Trace the run. Check the rafter stock.
Convert span, ridge thickness, pitch, overhang, building length, and spacing into a transparent common-rafter line and preliminary board count.
← Building span →↕ Ridge rise↗ Common rafter body← Eave overhang →↔ Ridge thickness
← Building length →↕ Rafter spacingRepeated rafter pairs
1 Enter the roof section
2 Plan repeated rafters
Results update automatically · verify the actual cut schedule with a qualified designer
Transparent geometry
Half-span, ridge deduction, slope factor, and tail.
The common run deducts half the ridge thickness from half the building span. Body and tail lengths use the pitch slope factor; repeated pairs follow on-center spacing.
Confirm the input pitch with the roof-pitch calculator.