Field guide
How to measure a roof for sheet
Get your material count right before you order. A quick field method for working out how many sheets and screws a simple gable roof needs.
01Measure the footprint
From the ground, measure the length and width of the building at the eaves. Note both numbers — these set the base area before the pitch is added.
02Account for the pitch
A steeper roof has more surface than its footprint. Multiply the plan area by a pitch factor: 1.05 for a low slope, 1.12 for a standard gable, 1.20 for a steep one.
03Add the overhangs
Add the eave and gable overhangs — usually 300–450mm each side — to your length and width before you calculate sheets.
04Count sheets by cover width
Divide the roof width by the sheet cover width (762mm for our corrugated sheet) and round up. Multiply by the number of rows up the slope.
05Add fasteners and waste
Budget roughly one box of screws per 20 sheets and add 10% material waste for cuts, laps and the ridge. Order the ridge cap to match the roof length.