How to budget for 200 m² of trapezoidal steel roofing

For this calculation, assume an ordered sheet length of 8 m. For an actual cutting list, check the allowances needed at the eaves and the upper edge. The example shows how the number of whole sheets affects the budget. An order for a real roof needs its own cutting list.

Take a T18 sheet with an effective cover width of 1.128 m. Eleven sheets cover only 12.408 m, so a 12.50 m wide slope needs 12. The two slopes therefore require 24 sheets. Their combined area based on effective cover width is 24 × 8 × 1.128 = 216.576 m². The sheets at the outer edges will need trimming.

The same T18 variant has an overall sheet width of 1.173 m. Measured across their full width, the 24 sheets total 225.216 m². Both areas describe the same delivery. To price it, check which width the supplier uses for billing and multiply the corresponding area by the quoted rate.

For the example, assume approximately €9.61 per m² of effective sheet cover and €12.04 per m² of roof slope for the specified installation work. The other figures are allowances. All prices exclude VAT. Unit rates are shown rounded, while the line totals use the unrounded rates. The figures illustrate the calculation and do not represent a supplier’s quotation or a market average.

Spread over 200 m² of roof slope, the total is approximately €27.47 per m² excluding VAT. It covers the listed items only. A roof with a different shape, supporting structure or scope of work needs a separate calculation.

The example excludes removal of the old covering, structural repairs, new insulation layers and waste disposal. Agree separately who supplies scaffolding, safety equipment and any lifting equipment needed to feed sheets onto the roof. If the building remains in use, equipment inside may need protection and installation may have to proceed in stages. Assign responsibility for each item.

Suppose removal of the old covering is added at about €6.94 per m² excluding VAT. For 200 m², that adds €1,388.70 and brings the illustrative total to €6,882.84 excluding VAT. Repairs to damage uncovered during removal would still be extra. List uncertain work separately so its cost can be assessed when the roof is opened up.

A different cover width can change the number of sheets needed. A deeper profile may require different flashings, and the design loads should guide the profile choice. Sheet thickness and coating also affect the price. Recalculate the cutting list before comparing rates so each option includes its actual quantity and accessories.

For long sheets, check vehicle access and how the crew will handle them. Shorter lengths introduce end laps and may increase the area ordered, but can be easier to manoeuvre on a restricted site. Base the quote on the planned delivery and installation sequence as well as the lengths the mill can produce.

Send each supplier a drawing of the slopes, a description of the supporting structure and the material specification. State whether the 200 m² is the measured area along the slopes. Ask for the sheet count, lengths and billing unit. List the flashings and installation tasks. With these details you can see whether a lower quote omits work needed to complete the roof.

On a refurbishment, agree what happens if removing the existing covering reveals damage. Some defects can only be assessed once the roof is open. Set out how the contractor will document them and how you will agree any additional work. This makes it clear which costs are fixed in the estimate and which depend on the building’s condition.