Multi-branch connection is a bit low

I rather see the mistake with the civil engineers. They installed the multi-utility connection. Then came the floor slab, underfloor insulation, and then the screed. And now we're missing about 8 cm there. Is there a regulation stating that the multi-utility connection must be flush with the top edge of the finished floor?

Not a regulation. But it has to fit. Otherwise, it won’t work. And whoever makes the breakthrough should measure beforehand. You can only have it corrected at no additional cost.

Is an extension to the top edge of the finished floor really necessary?

No, but highly sensible.

Will we have problems otherwise when the utility connections come?

The likelihood of that increases.

We would like to save the money if possible.

You can have those who messed it up pay for it.

I think it is more likely because we have a relatively high insulation build-up on the ground floor. The marking OK Rohfussboden was already correct. Only the insulation + screed was then added on top, so that overall the OK of the multi-service connection lies below the top edge of the finished floor. So I probably won't get around paying for the extension?

Insulation is common. Did the earthworks contractor know the top edge of the finished floor? If not, it is unpleasant that he did not ask and makes the discussion complicated...

Did the earthworks contractor know the finished floor level? If not,

... it is not uncommon for this to be the beginning of a wonderfully wrong house height :-(