01 / Find the horizontal run
Measure level from the eave to the vertical projection of the ridge. Use half the building span only when both runs are equal.
ROOF GEOMETRY / TOOL GUIDE
Understand your roof. Measure with confidence.
Roof cross-section01 / A–B
Measurement guide
Measure the right lines.
02 / Measure the vertical rise
Measure vertically from the eave level to the ridge. Use the same endpoints as the run; do not measure along the roof.
03 / Check a local pitch
Hold a level horizontally against a straight rafter. At 12 horizontal inches, measure vertically to the rafter. A 6-inch rise is 6/12, or 26.57°.