ᐅ Continue building after moving in?

I am planning to have a single-family house built (about 130m² (1400 sq ft)) and have received a fixed-price offer from a general contractor for various finishing stages. Now I would like to complete some "non-essential" rooms (basement, guest toilet, etc.) after moving in, and, for example, lay the tiles myself.

I assume that this would mean removing the entire "tile laying" trade from the contract. What needs to be tiled before moving in would then have to be contracted separately. Is my understanding correct, or is there another common practice? Based on your experience, is the cost for removing a trade fairly calculated, or do you usually end up paying more in such cases?

Thank you for your feedback!

As a rule, this is not fairly deducted because the contractor compensates for the lost business.

Such terms should be removed BEFORE the first signature on the contract; only then might you be able to expect a fair credit.

With some construction companies, you can also have just individual rooms tiled, painted, etc. A common example is an attic only prepared for finishing. In that case, the heating and screed might already be installed, and you do the rest yourself (only in the attic).