When calculating the cost of roofing works, we take into account technological allowances — the additional amount of material required for high-quality installation of the covering.
What allowances are
An allowance is a reserve of material laid in for edge cutting, overlapping of sheets and fitting to the roof dimensions. For example, built-up roofing sheets are laid with an 80–100 mm overlap, and trimming is required around the perimeter.
Why they are needed
Without allowances it is impossible to ensure the tightness and durability of the covering: the overlap protects the seams from leaks, and trimming prevents edge lifting and delamination. Saving on allowances leads to premature leaks and a shorter roof service life.
How this is reflected in the price
Allowances are already included in the per-square-metre price you see in the calculator and tariffs. They are not itemised separately — you immediately see the final cost including all technological requirements.
