Roofing Waste Calculator
Calculate roofing waste allowance for any material. Get precise overage for cuts, valleys, hips, and complex roof shapes. Free, no signup.
Draft Smart Component
Build a component with pricing, waste, and labour rules, then calculate cost from measurements
Component spec
Area measurement in square metres. Used for roofing, flooring, cladding.
Measurement
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Roofing waste — did you know?
Why waste matters
Under-ordering by 5% can stop a job mid-roof. Over-ordering by 15% wastes money (most suppliers charge restocking fees). Precise waste calculation saves both time and money.
Waste by roof complexity
Simple gable: 5-10%. Gable with 1 valley: 10-12%. Hip roof: 15-20%. Hip with valleys and dormers: 20-25%. Every valley, hip, or penetration adds ~2-3% waste.
Waste by material type
Concrete tiles: 5-10%. Clay tiles: 10-15% (breakage). Slate: 15-20% (splitting). Metal sheets: 5% (minimal cuts). Shingles: 10-15%. Membrane: 5% (cuts at upstands).
Skip and disposal
Strip a roof generates ~10-15 kg/m² of waste (old tiles + felt + battens). 100 m² roof = 1-1.5 tonnes. Order a 6-yard skip minimum. Some tile merchants take back undamaged stripped tiles.
Formulas used
Material with waste
qty = base_qty × (1 + waste%)
Waste by complexity
waste% = 5% + valleys×2% + hips×1.5% + dormers×2%
Strip waste weight
kg = roof_area × 12 kg/m²
Skip size
yards = roof_area × 0.06
Frequently asked questions
How much waste should I add for roofing?
5-10% gable, 10-12% with valley, 15-20% hip roof, 20-25% complex hip with dormers. Each valley/hip/dormer adds 2-3%.
How much waste for concrete tiles vs clay?
Concrete: 5-10%. Clay: 10-15% (breakage). Slate: 15-20%. Metal: 5%. Shingles: 10-15%.
How much skip space for roof strip waste?
~12 kg/m² of roof. 100 m² = 1.2 tonnes = 6-yard skip minimum. Some merchants take back undamaged tiles.
Best free roofing waste calculator?
One that factors roof complexity, material type, and disposal. This tool does all, free.