Roofing waste factor: how much extra to order
Typical waste percentages for gable, hip and complex roofs — and what pushes waste up.
The waste factor is the extra shingle material you order on top of the measured roof area to cover cuts, overlaps and starter and ridge courses. Order too little and the crew waits for a second delivery; order too much and you pay for bundles that go back to the supplier — if they take them.
Typical waste factors
| Roof type | Typical waste |
|---|---|
| Simple gable (two planes) | 10% |
| Gable with a few intersections | 12% |
| Hip roof | 15% |
| Complex: many planes, valleys, dormers | 17–20% |
What increases waste
- Hips and valleys. Every diagonal edge means angled cuts, and the offcuts rarely fit elsewhere.
- Number of planes. More planes means more edges and more partial shingles.
- Dormers, chimneys and skylights. Each one adds cutting around it.
- Shingle style. Some designer shingles have larger exposure and more waste per cut.
How to apply it
Multiply the measured squares by (1 + waste). A 30-square hip roof at 15% waste needs 34.5 squares — 104 bundles at 3 per square. Every Horus report includes a waste table from 0% to 22% with a suggested value based on how many planes the roof has, plus bundles and underlayment rolls for each row.
Do the math yourself with the shingle calculator.