Welds on the painted railing - assessment?

I would at least withhold the money that this damaged side panel costs. Send an objection to the invoice by registered mail and wait to see how they respond.

And the construction company doesn't give me much hope either and only points out to me what costs will come up if I go to court and lose. "Railings with more noticeable defects have already been accepted."

That clearly speaks against the construction company! So they knew that mistakes had already been made and still work with this company? Unfortunately, you really messed up twice there.

How do you come to that conclusion? Railings are very often provided by the client.

Sorry, I confused the construction company with the [GU]. Ashes on my head!

He is right about that. We hired the construction company to assist us with coordinating the trades and also with obtaining quotes. They said they only work with companies they know and have had good experiences with. Of course, we hoped to avoid the horror stories about construction that we had heard from friends and colleagues. Unfortunately, the metalworker was a complete failure. In my opinion, other trades also were not always 100% as expected. The only consistently good experiences we have had were actually with the craftsmen we hired ourselves based on friends' recommendations.

oh!
Then it is actually doubly bitter!
The construction company should then also be on it to give them a piece of their mind. I think the metalworker is also interested in working with the contractor in the long term. Not to mention the damage to their reputation...