Costs and planning
How do you compare two prices for steel sheet when sellers quote different metres?
The price per square metre is only useful once you have clarified which metre the seller is billing. The total sheet width is greater than the coverage width. Two different rates may therefore relate to a similar material cost. Instead of comparing the numbers alone, calculate the same list of sheets and add all mandatory order costs. Begin the comparison by identifying the steel sheet. The profile, steel thickness, type of coating and ordered colour should match. Also establish whether the sheet has an additional layer on the underside. A similar photograph and the same trapezoidal height are not enough. Two cross-sections may have a different coverage width and different load-bearing properties.
Which parameters must be identical?
Record the required lengths and number of pieces. If one supplier quotes material cut to the project, while another quotes only the available stock format, the difference in cutting layout must be taken into account. Do not assume that every offcut from a sheet can be used. The profile direction, the coating side and the required connections limit the possibilities for reusing offcuts.
How do you calculate two types of surface area?
Let us assume fifteen sheets with a length of 3.2 m. Their total length is 48 linear metres. For the selected T35 variant, we assume an actual effective width of 1.035 m and an overall width of 1.082 m. The purchase covers 49.68 m² of nominal coverage and 51.936 m² of overall area.
Both areas are correct if they are accompanied by the appropriate price unit. However, 49.68 m² should not be called the exact area of the finished roof surface without checking the cutting layout. The value describes the sum of the nominal coverage of the purchased sheets. Any edge cuts and transverse laps change how much actual roof can be covered.
Which rate means cheaper material?
Assume two hypothetical net offers for identical sheets. The first quotes €8.56 per m² of total area, the second €9.03 per m² of effective area. In the first, the cost is 51.936 × €8.56 = €444.57 after rounding. In the second, we calculate 49.68 × €9.03 = €448.61. The difference in material price is only €4.04.
The gap between the rates €8.56 and €9.03 looks more pronounced than the difference in the final totals. This is because they relate to different areas. The example does not show market prices. The amounts were assumed for practising unit conversion. Before purchasing, you must insert the current data from both offers and keep the same material parameters.
Why can delivery change the order?
Let us add contractual transport for €81.01 net to the first offer and for €67.12 to the second. The final totals will be €525.58 net and €515.73 net respectively. The second offer becomes cheaper by €9.85, despite the higher price of the material itself. This simple calculation shows why it is not worth ending the comparison at the cost per square metre of sheet metal.
Check what each delivery includes. The vehicle arriving is not the same as unloading or lifting the sheets onto the roof. Also establish the site access conditions. If one offer requires separate equipment on your side, its cost must be added to the comparison. Self-collection also has a cost and restrictions related to length and securing the load.
How should extras and lead time be included?
Flashings, fasteners and sealants should correspond to the same project in both quotes. Otherwise the lower total may result from an omitted item. Not everything has to be bought in one place, but the compatibility of components and the cost of each delivery must be checked. An overly general “accessories” item makes such a check difficult.
The date on which the construction is ready also matters. Early delivery may require appropriate storage, while a delayed one may disrupt the crew’s work. Do not assign an arbitrary amount to these differences. First establish the real consequences and conditions. A good offer specifies the material, quantity, date and the parties’ obligations clearly enough to plan the works.
What table should be prepared before deciding?
In one table record the profile, thickness, coating, colour, lengths and number of pieces. In the second row show the effective area and the total area. Then enter the price unit, material cost, extras and transport. Compare all amounts consistently as net or gross. At the end leave space for items not included in the offer.
For the decision, use the final total for the complete scope in accordance with the project. If the difference is small, clear arrangements and a suitable schedule may matter. It is not worth choosing unsuitable steel sheet just because it works out cheaper after calculation. The price should decide between correct variants, not replace checking their application.
Questions and answers
Is the price per total square metre unfair?
No. It is a correct billing unit if it has been clearly stated. It must be multiplied by the total area, not by the effective area.
Is it enough to know the roof area when buying?
No. The shape, dimensions and list of sheets are also needed. Only the cutting plan allows the quantity of material to be calculated and the full cost to be compared.
7 branches. Materials closer to your project.
