Extension planning for house from the 60s

First, I wait for the response from the Bau-Bürger-Büro, which informally provides the initial assessment of the buildability outside the building limits according to the development plan. If there is no complete rejection there, the idea can be pursued further.
There is then a "problem triangle" under the extension that needs to be optimized in terms of economic viability and technical feasibility:
- Relocate HA ($$$) + no basement ($)
- Build basement ($$$) + keep HA lines as they are and only "pass through" or move handover point ($ + feasibility?)
- Do not build basement ($) + drainage under extension not accessible (feasibility + future problems?)

And everything must be feasible while the house is occupied. So, for example, a new room should first be created before the one it replaces is "removed" (e.g. kitchen). Also, the parents' bathroom on the upper floor can only be renovated when a replacement with the children's bathroom is available.
The house’s structural integrity does not allow shifting walls. But widening a lintel or relocating a window is possible.

Not everything in life is plannable, and knowing now that there are 2 children living in the house, we certainly would have done a core renovation with different modification options before moving in. But some change requests and disadvantages only become apparent after living there for a while.

Specifically, I still have the question whether there is enough space to create a children's shower bathroom on the upper floor for my idea.


The washbasin and WC are already tight at the 2m line of the sloping roof. The shower must be a corner spar solution to still get through the door. The partition wall at the shower is 20 cm here and at the WC 30 cm.

An alternative room connection on the same area is only disadvantageous for the children's rooms with zigzag pathways and unfurnishable narrow room snakes:

Ideally, the extension should not have a flat roof and of course everything should be implemented with as few restrictions as possible while the existing building remains occupied. An extension to the east would be possible within the building window,

I consider your building window to be expandable if necessary, especially since it was set quite arbitrarily. In my opinion, a renovation in an occupied building strongly recommends an architect (whom I would not currently recommend to you in NiSa, but I am happy to advise personally). I consider own requirements for the roof shape to be too restrictive. Unfortunately, all your new remodeling ideas would build over the entrances, and the children's room gable windows are also not a small sacrifice.

It is progressing slowly. From the lower building authority, I have the statement that an exemption regarding the exceeding of the front building boundary is being considered.

Because of the supply lines, I would plan the extension with a basement. Then the existing lines can continue to be used and only the transfer point would be moved.
That should be more economical than relaying all the house connections from the street.

For the old children's room, I envision a dormer as a replacement for the windows. One possibility would be the following:

Brief update: We have now gone ahead with this solution and are waiting for the transfer of the idea into a real plan from the civil engineer. It does have the greater added value compared to the extension on the gable.

Update: The building application for the most recently presented solutions has been submitted.

This is what the approval planning looks like: