How can two sheet metal prices per m² give the same cost?

If the unit is unclear, request the price for one sheet of a specified length. Keep the prescribed laps in the installation plan. They follow from the profile geometry. Reducing them to “recover” a few per cent of material changes the joint.

Take a sheet with an overall width of 1.142 m and a cover width of 1.100 m. An assumed net rate of about €8.92 per m² of gross sheet area corresponds to €9.26 net per m² of cover. Multiply the unrounded gross-area rate by 1.142 and divide by 1.100. These figures illustrate the calculation and are not a current sales price.

At 5 m long, the sheet has a gross area of 5.71 m² and covers 5.50 m². Using unrounded rates, both calculations give €50.94 net after rounding. The higher cover-area rate therefore does not make this sheet more expensive. Compare prices on the same basis to find a real difference.

Keep the full precision until the last step. Rounding a square metre rate before multiplying by a large area can give a different total from the sheet-by-sheet quotation. Agree which value will be invoiced and which is for comparison only.

No. Compare the profile, steel thickness and grade, metallic coating and outer finish. Check colour and whether the sheet is for roofing or façade use. An anti-condensation layer creates another configuration. Profile height alone does not describe all these differences.

Compare cover width, available lengths and design conditions as well. Two T18 sheets need not fit together. A change in geometry can alter the number of runs and edge cuts. Similar prices per square metre can therefore lead to different order totals.

Identify the charging basis of each surcharge, for example for a coating, fleece or non-standard length. If the base price uses cover area and the surcharge uses gross area, convert them first. Adding the two numbers directly can give a wrong result.

Treat per-piece and delivery charges separately. Add the amounts before calculating an average cost per square metre of the order. The result depends on quantity. A fixed charge is spread over far fewer square metres on a small shelter than on a large industrial building.

Order sheets in specified lengths and whole runs. An edge strip may need trimming. Valleys or hips produce a different cutting plan from a simple rectangle. The unit rate does not tell you how much of the purchased sheet will stay on the roof. Use a sheet schedule.

Include flashings, fasteners, seals and labour. Ask for the sheets-only subtotal and the total for the full agreed scope. This shows what the roofing material costs and what the completed work costs. Itemise omissions instead of hiding them in an unexplained percentage allowance.

Use one comparison table for specifications and quantities. Enter the unit rate on the same area basis for each offer and show the price of the actual sheets. Add the other items and check the tax basis. Record the quotation date and validity, since both material and transport prices can change.

Base the decision on compliance with the design, total price and delivery scope. Confirm lead time, unloading and acceptance arrangements. A favourable rate helps only when it buys the right product in the required quantity. The two headline figures are just the starting point.

Keep both width measurements with the calculation. Without them you cannot reconstruct the converted rate later.