Why does a metre of roof panel cost differently from a metre of wall panel?

Snow and wind, among other things, act on the roof. A wall also carries wind load, but in a different arrangement. A wall panel priced lower does not therefore become a substitute for a roof panel. The saving must fall within the intended use of the product.

In one real product family, a PIR wall panel 100 mm has a U-value of 0.19 W/(m²·K). The roof variant with a 100 mm core achieves 0.20 W/(m²·K). Its total height including the trapezoidal profile is 140 mm. The example shows why you need to read how dimensions are stated.

Do not transfer these figures to every PIR panel. The parameter depends on the specific variant. In the offer, also check whether the core thickness or the dimension to the profile apex is given. Confusing these values makes it difficult to compare both the price and the thermal effect.

A profiled facing uses more material than its flat projection. The two sides may have different thicknesses. An example roof panel with facings of 0.5 and 0.4 mm is not the same order as the 0.5 and 0.5 mm variant. The price should be related to the full description.

Do not judge quality solely by the weight per metre. A heavier panel may have a different core, facings or thickness. The choice follows from the requirements, not from the principle that “heavier means better”. The coatings on both sides should match the actual working conditions.

For weight, also check the unit. A kilogram per linear metre is not always a kilogram per m². With a 1 m module, the figures are equal, but with a wider panel you must divide the mass per linear metre by the cover width in metres.

For the calculation, assume only 80 m² of walls at €33.56 net and 50 m² of roof at €38.19 net. The panels cost €2,684.80 and €1,909.50 net respectively. In total, this gives €4,594.30 net. These are agreed rates, not a current sales price list.

If, after cutting, 86 m² of wall and 54 m² of roof have to be purchased, the result rises to €4,948.42 net. The difference of €354.12 comes from the quantities. Accessories, delivery and labour are still missing. The quotation table should show the area purchased and the area obtained after installation.

On the roof, details for the eaves, ridge, edges and any penetrations are added. The wall has a plinth, corners and opening flashings. For the same area, a more articulated shape requires more terminations. The averaged percentage of extras can then deviate significantly from the quotation.

Calculate the lengths of flashings and the types of seals on the drawings. Do not enter one set of screws for both building envelopes. Fastenings must match the panels, supports and loads. The price of a complete detail is more useful than the cost of the folded sheet metal alone.

Roof panels often have to be lifted over the structure. Suitable equipment and safety measures are required. A long element reduces the number of joints but can make access more difficult. Wall panels also require safe lifting, especially with a heavier mineral wool core.

However, do not assume a uniform installation rate for all areas. Height, access and details matter. In a small pavilion, the minimum cost of equipment arrival can account for a large share. Compare the scope of completed works, not just the operating hour of the lift.

For a series of similar buildings, prepare common requirements, but calculate each structure. A change in the number of windows or the roof length can change the waste. Also agree on consistency of colours and coatings. Wall and roof panels are not always available at the same time.

Compile quotations separately for the roof and walls, then add them up. This shows where the difference arises. Choosing the cheaper item only makes sense after confirming the parameters of the entire system. A small difference in the panel price should not obscure the cost of execution.