WU concrete + flush-mounted boxes in the residential basement - how can this be solved?

Why can't a duct be installed to the fans?

Because the power connection of the fan is about 10cm inside the wall and has to be connected from the side.

Because the power connection of the fan is about 10cm inside the wall and must be connected from the side.

Well then; until now we were only dealing with shallow flush-mounted boxes. Now we are already halfway into the wall.

The fans had not been on my radar at all until now, before the conversation with the Bauherren-Schutzbund, as I assumed that the fan boxes including the power supply had been cast in... this is not the case, only the boxes of the fans were cast in. During an inspection today, the following became apparent:

Well, whoops.
It is time to focus less on sockets and more on displaying defects.

So, news from the experts. I have now spoken to two more civil engineers. The initial written statement from the Bauherren-Schutzbund was strictly correct according to the standard. However, the expert from the Bauherren-Schutzbund and another engineer added in a detailed conversation that this standard only needs to be met in extreme cases:

[*]If there is no standing, pressurized groundwater, the professional installation of flush-mounted boxes is not a problem, provided that not a whole series of boxes are installed in the wall. Three per wall would be the limit.

[*]In doing so, a 45mm deep box should be used
[*]Alternatively, it is possible to build up the exterior walls using 6cm wide Ytong blocks, thus creating an installation level. A separate ventilation for this is not required.

The crucial point is the professional execution with a box chaser and not with an angle grinder and a hammer.

Further insight:

[*]In a current new building, provided the basement rooms are expanded as living spaces according to the building description (which is the case for us), a flush-mounted installation is the expected type of execution and not a peculiarity.

[*]Usually, boxes and pipes would already be poured into the concrete here.
[*]Here the mistake clearly lies with the construction manager, who repeatedly emphasized (wuhahahaha pun intended) that this only happens "when the entire shell structure is complete."

This reassures me a lot now, as groundwater at our location, according to the municipality’s water expert, is very far away.

Today, ONE DAY before the electrical work begins, we received a supplementary offer from the electrician. It now states:
"Chiseling boxes / slots in concrete - the warranty for the WU concrete expires."

How would you handle this now? Thanks for the help!

"Breaking out sockets / slots in concrete - the warranty for the waterproof concrete expires"

Decline gratefully, I would definitely not accept that.

How much living space, in percent, do you lose due to the 6 cm facing wall?