When must additional costs for sampling be paid?

Hello dear construction forum,

we are also going to build. It will be a terraced end-terrace house with a general contractor (GU). The GU does 2 sample selections, once a technical sample selection, which includes everything that influences the structural engineering and construction planning, and a "classic sample selection." We have now completed the technical sample selection and face additional costs of nearly 10k. (electrical shutters, concrete light wells, circulation pump, larger meter box, different front door ...). So far so good. Now we have received an invoice from the GU in which we are asked to pay the entire additional costs of the sample selection immediately. (Construction has not yet begun).

The GU's terms and conditions state the following about this: 5. Additional services and special equipment will be billed separately according to the offer or on proof immediately after placing the order.

I don't quite understand the whole thing, but I find it difficult to pay 10k extra before the service is provided and before construction begins.

This brings me to the question: Is it "normal" and permissible to charge the additional costs of the sample selection immediately after the sample selection, or are these usually charged upon provision of the service?

Thank you very much in advance for your answers.

P.S. I couldn't find a thread on a similar topic. If I wasn't able to search properly, I would appreciate a link to the correct thread.

Why do people sign contracts that they obviously do not understand?!

Hello nightdance,

the question is justified and I have to take responsibility for it, I probably simply did not read the passage properly.

Unfortunately, my problem is not solved by that. Do I have to pay the costs of the sampling before the service is rendered?

Do I have to pay the sampling costs before the service is provided?

The general terms and conditions of the general contractor state the following:
5. Additional services and special equipment will be invoiced separately immediately after the order is placed, either according to the offer or upon proof.

Yes. Because it is contractually agreed.

But you can gladly ask your general contractor in writing if they will change it. However, the chances are slim.

Freedom of contract. You have accepted it. You can only ask for goodwill. Ask, do not demand.

Okay. Thank you very much for the answers.