Roofing material consumption
Roof area and amount of roofing material by pitch.
Enter the house dimensions and pitch – the roof area is calculated instantly.
How to calculate the roof area
The actual area of a pitched roof is larger than the house's footprint – the steeper the pitch, the longer the rafters. The area is calculated by dividing the footprint by the cosine of the pitch angle:
roof area = footprint ÷ cos(pitch)
Example: a 10 × 8 m house = 80 m² footprint, pitch 35°. Roof area = 80 ÷ cos(35°) ≈ 97.7 m² (plus overhangs). A gable roof has two planes, but they cover the same footprint – that's why it's calculated from the total footprint.
Battens and reserve
Roof battens are laid roughly every 0.3 m (depending on the roofing), which works out to ~3.3 running metres of battens per m² of roof. For the roofing material, allow a 5–10% reserve for cutting at edges, the ridge, and valleys.
Note: the calculation applies to a simple gable roof. More complex roofs with dormers and valleys have higher consumption. Prices and consumption are approximate.