How do you calculate the cost of a 200 m² trapezoidal steel sheet roof?

First, establish what the given area describes. The building’s footprint area is not the area of the pitched roof. Eaves and additional roof slopes also increase the measurement. If the 200 m² comes from the design, check whether it is the actual covering area. Do not add the slope again if it has already been accounted for in the documentation.

Next, prepare the cutting plan. Trapezoidal steel sheet is bought in sheets of a specific width and length. Offcuts occur at roof valleys, corners and edges. Not all of them can be reused. The required area therefore results from the layout of the sheets, not from a single fixed waste percentage. Two roofs of 200 m² each can have very different material consumption.

Let us assume that, after preparing the laying plan, sheets with a total nominal covering area of 210 m² are needed. In this example, the difference from the roof slope area results from the cutting plan. This is not a recommendation to add 5% to every roof. On a simple or more complex roof, the result may be different.

We compare 0.50 mm steel with a 25 µm polyester coating in two specific profiles. We use the catalogue gross prices per m² of covering. We do not add the standard side lap again, because it is already included in the effective width. The calculation does not yet include flashings, fasteners, delivery or the roofer’s labour. This makes it clear what each amount means.

According to the price list of 28 October 2026, the calculation is as follows:

The difference is €203.70 for the sheet metal in this example. Both profiles still need to meet the requirements for load capacity, support spacing and roof pitch. The calculation uses catalogue prices. Availability, commercial terms and delivery can change the quoted total.

In the same catalogue, 0.50 mm T35 steel with a 35 µm matt polyester coating costs the equivalent of €12.80 including VAT per m² of cover. For 210 m² the sheets alone come to €2688.00 including VAT. The choice of coating therefore affects the budget even with the same profile and roof geometry.

Steel thickness is a separate decision. It should not be reduced to keep the original total if the project requires otherwise. Likewise, a better coating does not compensate for insufficient load-bearing capacity. Before comparing quotes, establish the minimum technical specification. Only then assess the surcharges for aesthetics and additional properties. This way you avoid apparent savings consisting of buying incomparable material.

Flashings are calculated by the lengths of eaves, ridges, edges and roof valleys. Chimneys and other penetrations require their own sets. The number of fixings results from the design and the roof’s wind zones. It should not be an arbitrary average. Sealants and ventilation components are also added to the calculation.

If the roof is to be insulated, price the insulation, vapour control layers and the remaining parts of the building envelope separately. For an unheated building, an anti-condensation fleece can be considered if it suits the conditions of use. It is not a substitute for insulation. In every variant, check whether accessory prices are given per piece, per linear metre or per pack. Only after converting the units can they be reliably added up.

Add labour and logistics for the specified scope to the materials. For a renovation, include demolition, disposal, protection and structural repairs. Establish the cost of lifting the sheets onto the roof. Long elements may require more personnel or a lifting device. A transport price without unloading does not describe the full service.

Ask for a quote with an itemised breakdown and a validity period. It is good if the contractor confirms the measurement and the complete set of details. Also leave a reasonable reserve for damage to the old substrate that is revealed, if the renovation does not allow it to be assessed beforehand. The full cost of 200 m² is the sum of a specific scope. It cannot be reliably determined on the basis of the T18 or T35 symbol alone.

When comparing two quotes, keep the same cutting assumptions. One quote may contain more material due to a cautious allowance, while the other assumes full use of offcuts. Ask for this difference to be explained on the drawing. This will let you assess whether the lower total results from a more favourable price or from omitting some of the required sheets. It is also worth establishing the rules for any additional order and its transport.