Terraced house on a 240 sqm plot - fundamental questions / feasible?

You only have real certainty once you have commissioned a geotechnical report. It includes, alongside the foundation recommendation, notes on how the basement excavation should be carried out and how or if the slopes need to be secured. But such a securing measure doesn't have to be that dramatic; given the high price of the project, that wouldn't deter me anymore. Even without a basement, a strip foundation may need to be excavated next to the garage for the floor slab, and there too, securing against slipping may be necessary.

Volume discounts are marginal for a row of three houses and not yet present for a semi-detached house ... interfaces must definitely fit together ... with an identical clone there is a fee saving of 5% - maximum.

Missed it. I understood it differently in our case. Our architect "accepted" several houses from a shell builder and thereby gave him security. Thus, the surcharge for the WU basement, for example, was comparatively small (<10k euros). Of course, I can't provide proof, only compare our first and second offers.

...the neighbor's garage now gives us ... quite a headache. ...additional security measures just get more expensive (5k? 10k? 20k? 50k?), or could the entire project fail later because of this?

That was exactly what I didn't want to achieve. 1. Construction soil report: Provides security during basement construction but in this case also shows how the boundary is constituted. 2. Surveying the property (including the neighbor's garage). This way you can detect execution defects (in theory, 2cm distance to the boundary should have been kept). Both points together cost about 2-4k euros and should logically be invested before purchase. So now to reality, purely my personal view. If you want to do this, you need an individual plan that addresses the framework conditions. Everything else quickly leads you into problems with general terms and conditions and contracts for work, where a price must be sold and the rest is revealed later.

Good morning everyone

Thank you again for the responses, the colleague from the building authority was indeed impressed by the good preparation. Regarding boundary construction, a procedure for evidence preservation was recommended; basically, several people in the area have already built a basement directly on the neighbor's garage without anything major going wrong. Nevertheless, the evidence preservation procedure before the start of construction sounds sensible to us.

In addition, even within the building authority there was disagreement about whether a roof terrace with a maximum height of 4m may be constructed on the garage, or whether the state building code applies, which only allows a maximum height of 3m as boundary construction. This will still be clarified, because the development plan itself actually contradicts here.

Exciting topic

If a roof terrace is built on the garage, then you can set up the garden chair directly in front of the neighbors' bedroom.

If a rooftop terrace is built on the garage, then you can set up the garden chair directly in front of the neighbors' bedroom.

No, I can't, because in the row houses no windows are allowed on this side (i.e. at the border to the neighbor's garage). It is a "dark wall".

OK, understood! I thought there could be some on the upper floor.

Personally, I don't want it if the neighbor looks over directly at me from the roof terrace elevated at the corner of the house.