Roof Sheet Calculator
Calculate roof sheet quantities — corrugated iron, polycarbonate, profiled metal — from roof dimensions and pitch. Account for laps and waste. Free, no signup.
Roof Area Calculator
Calculate actual roof surface area from plan dimensions and pitch
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Roof sheets — did you know?
Effective coverage width
Sheets have a nominal width and an effective width (after side laps). Corrugated 1000mm profile: ~750mm effective (250mm lap). Box profile: ~1000mm effective (50mm lap). Always use effective width for sheet count.
Sheet length calculation
Sheet length = rafter length + overhang + 50mm trim. If rafter exceeds available sheet length (typically 6m), use two sheets with 200-300mm end lap. Lower pitch = larger end lap.
Polycarbonate vs metal
Polycarbonate: same profile, lighter, UV-coated. Coverage calculation is identical. But poly needs more fixings (every corrugation) and wider lap sealant.寿命: 15-20 years vs 40+ for metal.
Flashing and accessories
Ridge flashing: 1 per 3m of ridge. Apron flashing: at top of lean-to roofs. Verge trim: at gable ends. Closure strips: foam strips sealing corrugation gaps at ridge and eaves. Budget ~15% of sheet cost for accessories.
Formulas used
Sheets per slope
sheets = ceil(roof_width ÷ effective_width)
Sheet length
length = rafter_length + overhang + 50mm
Total sheets
total = sheets_per_slope × number_of_slopes
Fixings
fixings = area × 8 per m²
Frequently asked questions
How do I calculate corrugated roof sheets?
ceil(roof_width ÷ effective_width) per slope. 10m wide roof at 750mm effective: 14 sheets. Sheet length = rafter + overhang + trim.
What is the overlap for corrugated sheets?
Side lap: 1 corrugation (~250mm). End lap: 150-300mm depending on pitch. Lower pitch = bigger end lap.
How do I calculate polycarbonate sheets?
Same as metal — same profile, same effective width. But poly needs more fixings (every corrugation) and wider sealant.
Best free roof sheet calculator?
One that handles effective width, laps, sheet length, and fixings. This tool does all, free.