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

Good evening,

we have commissioned a developer to build a single-family house with a basement. Three of the four basement rooms will be fitted out as living space or an office.

We have 24cm thick waterproof concrete basement exterior walls. For me, it was clear from the start that in a new building the electrical and network sockets would of course be installed flush-mounted. I find surface-mounted trunking completely unacceptable, especially in living spaces.

This has been discussed multiple times with the developer, and the response has always been "No problem, there have never been any issues with this." However, the electrician recently raised concerns, and the developer now agrees with him.

Just asking the group: Where is the risk here? I thought either the concrete is waterproof or it isn’t?

Are there any guidelines on how deep a flush-mounted box may be set or other experience-based values?

Surface mounting is unfortunately a huge red flag for me – precisely for this reason we decided on a new build so that my office rooms would not show anything like that.

There are also decentralized room ventilators in the basement rooms, which also need an electrical connection in the concrete.

What options are there for this?

Many thanks!
DR

We have 24cm thick WU concrete basement exterior walls.

And that is exactly the minimum thickness needed to make the wall watertight. With WU, the watertightness depends on the thickness of the material. WU itself is waterproof but still vapor-permeable. Will there be anything added on the outside? Because of residential use and such?

There are basically only 3 options.

1) Electrical installations inside the interior walls of the basement

2) Installation level on the exterior walls (has the advantage of significantly improving the concrete look/coziness; but should be planned by a professional due to the aforementioned vapor permeability of WU)

3) Have thicker exterior walls made

Isn't the minimum thickness 20cm?

It depends. Depending on the manufacturing method and load class, at least 24cm are also recommended.

So, for example, with pressing water and in-situ concrete.

There are standard and deep flush-mounted boxes. For 1 to 2 cables, you can use standard ones; for more cables and possibly certain applications, deep ones must be used. Do not forget cable routing on/in concrete walls. If it is only one wall per room, possibly clad with drywall and install the flush-mounted boxes there.

It’s the same for me; I also don’t have flush-mounted boxes in the WU exterior walls. I have planned most of the electrical installation in the masonry interior walls as much as possible. However, only one room in the basement will be more livable for me; there I will probably clad the exterior walls with Fermacell. There are versions that already have a thinner layer of polystyrene on them, so that standard hollow-wall boxes will suffice. There are also baseboard channels where cables can be accommodated along with compatible sockets, etc., so that everything looks seamless. In an office room, dado channels make sense in certain places because many sockets, LAN, etc., are needed there and a certain flexibility is desired.