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⚠️ Approximate estimate, based on average industry rates. Verify against the manufacturer datasheet.
The actual roof area is always larger than the building footprint — the pitch factor sets it (at 30° the area grows ~15%). Add overlaps and cutting to the covering: ~5–8% for metal sheets, ~10% for bitumen shingles. The waterproofing membrane is laid with 10–15 cm horizontal overlaps.
Batten spacing depends on the covering — typically 350 mm for metal tile profiles, while shingles need continuous decking. The calculator counts covering, membrane in rolls, battens in linear metres and screws, and expert mode lets you tune overlaps and spacing to a specific profile.
Pitched roof covering area is greater than the building plan area. Pitch, overhangs, number of slopes, valleys, dormers and chimneys all matter. Enter actual plane dimensions or use a pitch factor, then add a reserve appropriate to the covering.
Membrane, battens and fixings are calculated for the selected roof system. Ridge, verge, eaves and valleys must be entered in linear metres, not derived from square metres alone.
The steeper the plane, the longer the slope from ridge to eaves. Measuring the actual sloping length of each plane is most accurate.
Less for a simple gable roof and more for a complex roof with valleys and many cuts. The exact allowance comes from the manufacturer and layout.
No. It calculates covering and accessories. Rafter section and spacing require structural design.