Mold in the GU bathroom refuses to respond

Maybe there is a confusion here between developer and construction company/general contractor? A developer is not obliged to let anyone in, as the property belongs to them until full payment is made. With a BU/GU it looks different.

He is a GC, not a developer. We also think that he adds more than the agreed 10% to the quotes. We never get the base offer for the change orders, only his. We are considering withholding the remaining amount at the end and settling it in court. You can't talk to this gentleman in a reasonable way; he is the big shot, in the business for 30 years... We suspect that his employees ventilated too little. There is no mold like this in any other house.

He is a general contractor, not a property developer. We also think that he adds more than the agreed 10% on the offers. We never get the base offer for the change orders, only his. We are considering keeping the remaining amount at the end and settling it in court. You cannot talk to this gentleman in a reasonable manner, he is the big shot, in the business for 30 years... . We suspect that his employees did not ventilate enough. There is no mold like this in any other house.

If he is the general contractor, it is your house that he is building. There has to be a key for that. What does your external construction supervisor say? I hope you have one. Building without one and being an amateur is almost grossly negligent...

If it is a GC, it is your house that he is building. There must be a key for that. What does your external construction supervisor say? I hope you have one. Building without one and being a layman is almost grossly negligent...

Yes, we have one, he is on the construction site today. He has already said that the mold must be removed. He will also prepare an expert report for this. If the GC does not remove it, would it be an option to withhold the remaining amount and then settle this in court?

Yes, we have one, he is on the construction site today. He already said that the mold has to go. He will also prepare an expert report for this. If the general contractor does not remove it, would it be a possibility to withhold the remaining amount and then settle this in court?

Very good. The problem with the key still remains. We and the external construction supervisor are each getting one, so that we can always enter.

Get the key! This is YOUR house!

In any case, a complaint about defects (by registered mail with return receipt) should be sent to protect your interests.
You can always still waive it

A registered letter with return receipt is often not effective. If the person concerned is not reachable and does not pick up the letter at the post office, it is not delivered. This can be fatal, especially when deadlines must be met.
I have (especially) important letters/documents delivered by a bailiff. That way I am truly verifiably (!) on the safe side and there are no misunderstandings, especially regarding the content. The costs are manageable.

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But why don’t you, as the builder, have a key to your property? I am always amazed that people go along with that. If you really build with a general contractor and really are the builder, in the end you are even responsible for everything that happens on your land, on your construction site.
That’s not called builder_M_A_S_T_E_R_ for nothing...
You should have a key to check whether there are any skeletons in the closet....
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Partial knowledge: Isn’t there something about accident safety? I think it was mentioned here in the forum once.