Final costs only after structural analysis and heat demand calculation?

I'm a bit confused because of a passage in the construction service description that says the final costs will be determined after structural calculation, heat demand calculation, etc. Is that usual? Best regards Peter

No, that is not normal. That would mean you don't have a fixed house price to plan with. The house supplier could simply increase the house price afterwards. We received a fixed house price from the general contractor long before the structural and heat demand calculations were done; the general contractor must include that in their offer calculation. After our structural calculation was done, a wall on the upper floor had to be widened and a large steel beam had to be planned into the ground floor ceiling in the living area.

Best regards Sabine