How much sheet metal and installation should you budget for on a 200 m² roof?

In the example, we assume 200 m² of actual surface to be covered. The project specifies the profile and supports. The cutting plan gives an order corresponding to 218 m² of effective width. The difference results from the specific division and cuts. It is not a universal allowance for every roof.

With rectangular roof slopes, the result may differ from that with roof valleys and many penetrations. Do not automatically add a fixed percentage without checking the layout. A well-prepared cutting plan shows the number of sheets, their lengths and which fragments will be used.

For the example T35 profile, the overall width is 1082 mm and the effective width is 1035 mm. At a price of €8.80 net per square metre of total sheet area, the cost per square metre of effective cover is approximately €9.20 net. This follows from the calculation €8.80 × 1082 ÷ 1035.

For the rest of the calculation we use the rounded net rate of €9.20 per m² of effective area. An order of 218 m² then costs €2,005.60 net. This is the cost of the sheets alone in the variant adopted. The steel thickness, the coating and the actual quotation may change the amount.

Do not add the side lap a second time if the calculation is already based on the effective width. However, the cutting plan and any longitudinal laps must be taken into account. These are separate issues. Mixing them can lead to both a shortfall and double counting of some material.

To the assumed cost of the sheet metal let us add €439.75 net for flashings and €150.44 net for the fasteners and seals. Let us assume €208.30 net for delivery and €1,573.86 net for installation within the specified scope. The total for the example is €4,377.95 net.

Converted to 200 m² of roof area, this gives around €21.89 net per m². This result covers only the items listed. It does not include the structure, insulation, gutters or removal of the old roof. If these are needed, they must be added to the cost estimate.

The installation rate depends on the actual work. Access, height, sheet length and the number of details matter. Do not treat the assumed amount as a price suitable for every building. The contractor should quote the identified scope together with the necessary equipment.

Let us assume a surcharge of €2.08 net per m² of the total for felt. For the same widths, this corresponds to around €2.17 net per m² of effective area. At 218 m², this gives €473.06 net. Adding this to the previous total gives €4,851.01 net.

This is a separate calculation variant, not a mandatory addition to every roof. The fleece temporarily retains condensation and needs conditions to dry out. It does not replace insulation or a designed underlay. Its purpose must be assessed within the entire system.

Also include edge preparation in the cost estimate in accordance with the instructions. The non-woven fabric should not draw rainwater from the eaves and laps. Purchasing a sheet with an additional layer alone does not cover all installation requirements. Proper ventilation is also needed.

Compare profiles, thicknesses and coatings. Two quotes for 200 m² may describe different quantities of purchased sheet metal. Ask for a list of lengths and the billing unit. Also establish whether the price includes all flashings from the drawing and what installation scope has been assumed.

When replacing the covering, add dismantling and an assessment of the supports. Their repair is not always known before the roof is exposed. It is worth establishing how such a scope will be settled. Do not hide uncertainty in one seemingly precise rate per metre.

Finally, check the deadlines, unloading and validity of the quote. A roof installed in stages may require several deliveries and the return of equipment. The choice should take into account the cost of the entire defined task. Only then can you assess which proposal actually fits the budget.

It is worth keeping the cost estimate with the date and version of the cutting plan. If the eaves length or the position of the roof penetration changes later, it will be easier to determine which quantities and costs need updating.