This guide explains exactly when to use 10%, 15%, or 20%+ waste factor on a shingle order. Simple gable roof: 10% waste. Hip roof: 12-15%. Cut-up roof with multiple valleys, dormers, skylights, or steep cricket flashings: 15-20%. Steep pitch (10/12+) or laminated/architectural shingles with random offset: add another 2-3%. Includes worked examples for three roof types and ties directly into our Waste Factor and Shingles calculators.
The waste factor is the percentage added to the measured roof area to cover cuts, offcuts and damage. Choose it from the shape of the roof rather than from how careful you intend to be — it is geometry, not workmanship.
| Roof type | Waste | Area to order against | Extra squares |
|---|---|---|---|
| Simple gable, no valleys | 10% | 2,460 sq ft | 2.2 |
| Gable with dormers | 12% | 2,504 sq ft | 2.7 |
| Hip roof | 15% | 2,571 sq ft | 3.4 |
| Cut-up hip with valleys | 18% | 2,639 sq ft | 4 |
| Complex, many planes | 20% | 2,683 sq ft | 4.5 |
A gable roof has two rectangles and four cut edges — two rakes on each plane. A hip roof of the same area has four planes and eight diagonal cut lines, and a diagonal cut through a shingle produces two triangular offcuts, neither of which fits anywhere else. Add a valley and both planes running into it are cut on the diagonal as well.
That is why the figure is a property of the roof shape. A very careful crew on a cut-up roof still generates 18% waste, because the offcuts genuinely have nowhere to go.
Unopened bundles usually go back for credit. A second delivery for four bundles costs a trip charge and stops the crew for half a day, and on a roof that is stripped and dried in only with underlayment, half a day is a weather risk as well as a cost.
Ten percent for a simple gable, twelve with dormers, fifteen for a hip roof and up to twenty for a complex roof with several valleys and planes.
A hip roof has four planes and eight diagonal cut lines against a gable's two planes and four rakes. A diagonal cut produces two triangular offcuts, neither of which fits anywhere else on the roof.
Yes, though a smaller figure is usually enough because underlayment is cut far less than shingles. Roll coverage is also stated before overlap, so plan on about 10% less usable coverage than the label.
Slightly over. Unopened bundles usually go back for credit, whereas a second delivery for four bundles costs a trip charge and half a day of lost work.