Construction contractor billing according to VOB - How to calculate?

Hello everyone,

how does a shell builder calculate according to VOB?
When I calculate with the exterior dimensions of our house, I come to about 30m2 less than in the offer.
I haven't even deducted 2 large window areas and the garage door.

Regards

The shell construction contractor considers volumes and not the living area.

If 260m2 of brick façade are listed in the offer, but it is actually only 230m2, what then?

Openings in the facade are not deducted. There is some minimum dimension when this must be considered in quantity calculations. Otherwise, you would have to subtract every little thing. Is that correct? Just ask him.

No, I'm telling you that I have a 30m2 difference without having deducted anything.

Then it is usually this percentage cheaper. Unless it is a fixed price offer. Sometimes you win, sometimes...