A 200 m² trapezoidal steel roof: how to work out sheet quantities and costs

Assume two simple slopes, each 10 m along the eaves and 10 m from eaves to ridge. Together they measure 200 m². This example excludes valleys, chimneys and roof windows. On a real roof these features can change the cutting plan, flashing quantities and labour time. Check all dimensions before production.

Take a 10 m sheet with a cover width of 1.10 m. Each slope needs ten runs because nine cover only 9.90 m. The order for both slopes is therefore 20 sheets. Their combined nominal cover area is 220 m². Trim the edge sheets to suit the actual roof width.

If the overall width is 1.142 m, the same sheets total 228.4 m² before overlaps. Keep gross sheet area and cover area separate when comparing prices. Confirm that sheets of this length can be manufactured, transported and lifted. Shorter sheets would alter the joints and material quantities.

Do not automatically deduct a planned roof window from the sheet order. The opening may be cut from a whole run. Check whether the offcut can be used elsewhere. The window also needs its own support and finishing details.

Assume a net price equivalent to about €9.73 per square metre of cover. On the unrounded rate, 220 m² costs €2,141.12 net. Price the remaining items separately. The euro figures below are rounded after conversion from the example in PLN, so displayed line items can differ from the subtotal by a cent. These are calculation assumptions, not a contractor’s price list.

In the actual quotation, each line should have a description, unit and quantity. A lump sum for accessories is useful for a preliminary budget. Replace it with an itemised list before ordering.

Assume labour equivalent to about €11.12 net per square metre of roof slope. For 200 m² the unrounded rate gives €2,224.54 net, bringing the example total to €5,269.39 excluding VAT. Both labour rate and scope are assumptions. Obtain a quotation for the actual site and structure.

Ask whether labour is charged on roof area or sheet quantity. Establish who fits flashings, lifts the sheets and secures the work area. The example excludes removal of old roofing, structural repairs, insulation, gutters and additional equipment. Price these separately if required.

Valleys, windows and chimneys increase cuts and detailing. Restricted access may require reloading onto another vehicle. Defective supports can halt installation even when delivery is complete. Base the contingency on identified work and include all known items in the estimate.

Steel thickness, coating and anti-condensation fleece also affect cost. Compare options for the same profile and cutting plan. A different cover width can change the number of whole runs. A lower square metre price may still produce a higher order total if more material is needed.

Supply a roof drawing, site location, support spacing and required scope. Request a material specification and an itemised accessories list. Compare all prices on the same tax basis. Establish the final VAT-inclusive amount for the goods and services ordered at the applicable rate.

Check how long the quotation is valid and when quantities can still be changed before production. Agree who signs off the dimensions and arranges unloading. A complete schedule gives you a budget for the 200 m² roof. Multiplying its area by a headline rate gives only a starting point.