How much does metal roofing cost for a roof area of 100 m²?
Metal sheets and roofs
The cost of metal roofing for a 100 m² roof depends not only on the price per metre but also on the coverage width and the layout of the sheets. A profile that is cheaper per unit may require a larger purchase after cutting. We show this using a simple example of two roof slopes and catalogue prices from 28 October 2026. The calculation covers the sheets only. Flashings, fixings, delivery and installation require a separate schedule for the given building. Let us assume two rectangular slopes, each 10 m wide and 5 m long measured along the slope. Together they give 100 m² of coverage area. We assume sheets run the full length of each slope. There are no roof valleys or additional penetrations.
What roof does the example cover?
Let us assume two rectangular roof slopes, each 10 m wide and 5 m long measured along the slope. Together they give 100 m² of covering area. We assume sheets running the full length of each slope. There are no roof valleys or additional penetrations. This is a simplified model to show the effect of covering width.
The actual order must also take account of the eaves and ridge details. The production length may differ from the roof slope area itself. If transverse joints are needed, further conditions apply. The list below should therefore not be copied to your own roof without a survey. Its purpose is to explain the calculation, not to create a universal set for every 100 m².
How many sheets are needed with 1.10 m coverage?
For the example T18 with a covering width of 1.10 m, nine sheets give only 9.90 m. That is 10 cm short of the slope width. Ten sheets are therefore needed for one side and twenty for the whole roof. The last strip must be adjusted in the cutting plan. The missing section cannot be left out, nor can the overlaps be reduced.
With the assumed length of 5 m, the total nominal covering area of the purchased sheets is 20 × 5 × 1.10, i.e. 110 m². This does not mean that the roof itself suddenly has a larger area. The difference results from fitting full widths to the area. With a different slope width, the same profile may produce significantly less waste.
This example also shows the risk of an automatic allowance. Adding 5% to 100 m² would give 105 m², which is less than results from the assumed T18 list. This does not mean that 10% is always needed. A different slope width would be enough for the strips to work out more favourably. A survey and sheet plan should therefore precede determining the material surplus. If the cutting plan provides for reusing a side offcut, it must retain a suitable joint edge. Its width alone does not confirm that a further tight strip can be made from it.
Can the narrower T35 result in a smaller purchase?
For the T35 model with a covering width of 1.035 m, ten sheets are also needed per slope. Nine give 9.315 m and are not enough. Twenty sheets of 5 m have a total nominal covering area of 103.5 m². In this specific arrangement, that is 6.5 m² less than in the T18 example.
It does not follow from this that T35 always produces less waste. A change in roof width can reverse the result. That is precisely why a strip plan is needed. The possibility of using offcuts and the detail of the side edges must also be checked. The higher profile must be suitable technically and visually. The purchase calculation does not replace an assessment of load-bearing capacity or permissible pitch.
What amounts result from the catalogue prices?
For 0.50 mm steel and 25 µm polyester, the price list of 28 October 2026 allows the following gross calculation:
| Variant | Purchase by coverage | Price per m² of coverage | Sheet metal only |
|---|---|---|---|
| T18 from the example | 110 m² | €10.34 | €1137.40 |
| T35 from the example | 103.5 m² | €11.31 | €1170.59 |
The two cutting plans leave a difference of €33.19 in the cost of the sheets. The quantities ordered narrow the gap suggested by the unit prices. The example uses catalogue rates. Discounts, the way the supplier bills the sheets and delivery terms can change the final quote.
Which costs are not yet included in the table?
Both roofs need flashings for the eaves, ridge and sides. Fasteners, seals and the ventilation provided for in the solution are added. The cost of these items depends on the actual lengths and details. They should not automatically be multiplied by 100 m². Some are sold by the piece, some by the linear metre or in packs.
There is also no cost for the substrate and installation. For a renovation, dismantling, disposal and any structural corrections must be calculated. Delivery may require unloading long sheets. If the building is heated, a full insulation system is added. The anti-condensation fleece on the underside of the sheet is not a substitute for these layers. Any surcharge for it is taken into account separately.
How do I transfer the calculation to my own roof slope?
Record the width of each roof slope and divide it by the coverage of the chosen model. Round the number of strips up, then determine their lengths together with the details. For angled sections, prepare a cutting plan drawing. Do not use the overall width as the covered area width. The side lap is part of the joint and must not be counted twice.
Ask for a sheet schedule that explains the final purchase area. Compare it for all the profiles under consideration. Only then multiply the quantity by the correct price and add the rest of the scope. Such a calculation is more useful than a single promise of a price for a “100 m² roof”. It shows where the cost arises and what will actually change with the choice of material.
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