Construction contract - What is regulated only after signing?

Hello.
I am currently looking at the draft construction contract from the general contractor.
We will also have it reviewed by experts.
I’m just curious about what else is agreed upon with the contractor after signing the construction contract. I’m not very familiar with what is already included in the construction contract and what is agreed upon later with the general contractor. A complete planning already in the construction contract is hardly feasible, I think. Or am I mistaken?
A few examples of what I could imagine being agreed upon only after signing the construction contract in a supplementary agreement:
1. The electrical planning
2. Whether a bathtub is installed in the bathroom or not
3. Whether to commission a gravel bed as a splash guard around the house
4. Which floor coverings you want in which room
5. Whether to build with a garage or carport
6. Whether to commission the embankment and filling of the property
7. Whether to have a wood stove installed
8. Which plaster quality Q2 or Q3 you want in which room and which plaster type in which room
9. Whether to transfer the coordination of the house connections (internal development)
10. Which special sanitary objects (models/manufacturers) you want
11. Whether a parking space is commissioned
12. Whether a terrace is commissioned

Maybe you also have experience with what else is only finally regulated after signing the construction contract.

I’m looking forward to your experiences... :)

Well, I would include everything where you see a cost risk or want cost certainty.

I can only recommend requesting offers as comprehensively as possible. Back then, we also initially wanted to build with a general contractor, at least for the staircase, excavation (different soil classes), electrical equipment (number of outlets, switches, circuits, bus?), sanitary fixtures, and floor coverings, which we first sampled and obtained offers for to get cost control. If you have that, why not make it part of the contract?

The things mentioned were important to me and ultimately showed that we would have ended up with the general contractor in the architect’s area - if not even beyond. The plumber was extreme, the electrician as well...

The responses from the general contractors asked varied. Some said, “no, we only do that after signing”… one can only speculate why [emoji6]
…others had no problem with it and were open to it.

Maybe you also have experience with what else is only finally regulated after signing the construction contract.

You should agree on most of the things mentioned earlier. Otherwise, it will get quite expensive later, because the contract is set and no one else will be able to conjure up the chimney flue for you.

As an example, the electrical planning. Of course, you don’t have a detailed electrical plan yet. But you can already fix the number of sockets or the additional cost for extra sockets. The same goes for network sockets, satellite connections, or, if you like, the number of two-way switches.

Things like plaster quality, etc. are in my opinion mandatory. Or the bathtub, write that directly into the contract (or already priced as an option, in case you’re not sure yet).

Things like a carport can also be commissioned separately later, so that’s okay. But: You still need to decide on this soon and assign costs if you want to include it in the financing.

I can only advise to have everything included in the contract beforehand. Afterwards it will only get more expensive...

From the above-mentioned list, only the quantity of sockets, etc., was specified in our construction service description; the contract was only by handshake and it was unclear where they were located. The heating was specified, brand and type. Sanitary installations Kalldewei, Duravit, or V and B, tile price, size, who was to select them, etc.

Where you want security, include it. We only did the electrical work in detail later with the electrician, it was about 20% cheaper. The same goes for the balcony railing. At least that is our experience, which largely matches the experiences of acquaintances.