Toilet installation - Is a pre-wall element necessary?

Hello everyone,

I have a technical question that Google couldn’t answer for me, or probably I just searched the wrong way...

It’s about the following: We are in the process of buying a house. Unfortunately, we will only get the key in two weeks and will then plan with a specialist company, but I would like to inform myself beforehand.

The house unfortunately has only two very small bathrooms. Currently, the old toilets with the visible flush tanks are installed. We would like to change that. I thought a pre-wall frame, which is then clad and has a shelf on top after completion, was the only option.

But now I have heard that someone installed the toilet installation in the wall behind it. At the moment I doubt that this works and is allowed to be done, but I am not an expert. Of course, the wall has to be thick enough so that the stuff doesn’t fall out the other side.
Is such an installation really okay? Can the parts for the toilet simply be set inside the wall? The pictures of the pre-wall frames show huge parts, and I can’t imagine that such large holes are allowed to be cut into the wall.

Is there any alternative to the pre-wall frame besides the ugly box like before?

Best regards

If this recess bothers you, you can make the cladding (drywall) full height to the ceiling, and thus it will no longer be a visible box.

The shelf does not disturb. It is more about the space requirements of the pre-wall element since the room is quite narrow.

I have never heard of that before; probably only a professional can help you with that. The structural integrity also plays a role in this. I also wouldn't know how all the drain pipes are supposed to be routed into the wall, as they are not even 5 cm. Besides, you need some kind of steel construction, as the toilet also weighs quite a bit and the pipes need to be hidden as well. But I'm not an expert; maybe it is possible. We are also talking about 20 cm of space savings versus a lot of work.

I thought a pre-wall element, which is then covered and after completion has such a shelf on top, was the only possibility.

Or it is built into a solid wall.

Or the "pre-wall" is bulged backward (if not on an exterior wall).

There are no alternatives.

But I have heard that someone installed the installation for the WC in the wall behind.

But in that case, the wall was either correspondingly thicker or otherwise planned.

Is such an installation really okay? Can you just set the parts for the WC into the wall?

In retrospect, actually not.

Of course, you cannot simply reduce an exterior wall by half to install a pre-wall or a pipe there. That is not possible, not even in interior walls that have a structural function. 11.5 cm walls, on the other hand, are too narrow to build anything underneath.

The pre-wall installation was invented precisely for such problems: so that it can be placed _in front of_ a wall without interfering with the statics or having ugly pipes visible.