How to price a re-roofing job
The area along the slope is larger than the footprint of the building. The calculator divides the footprint by the cosine of the pitch to get the sloping area, then works out tiles, battens and membrane from it.
How many tiles?
Tiles per square metre depends on the tile and the roof pitch and lap. Use the manufacturer's data, because concrete interlocking tiles need far fewer per square metre than plain clay tiles or slates.
Scaffold, access and disposal
Scaffold is often one of the biggest single costs on a roofing job, and removal of the old covering takes time and disposal costs. Both are included as inputs you can change.
Not included
Ridge, hip and valley pieces, lead work, chimney repairs and timber repairs are not in the quantities. Roof work at height is high risk, so plan access, edge protection and weather carefully.
Set your hourly rate with the freelance rate calculator.