Terraced house: Remove concrete partition walls to neighbors or not?

It is about the planned extension for our terraced house, which is currently being renovated.

Originally, there was a patio on the garden side. We want to close it off and additionally add a one-meter-long extension. On both sides, the neighbors' terraces are separated by about 2 m long concrete walls, 32 cm wide, of which 16 cm are on our property and 16 cm on the neighbors’ properties. The concrete walls extend about one meter into the ground and are firmly connected to the house there, essentially as part of the foundation. Above ground, the concrete reaches one meter high and glass blocks sit on top.

When we spoke with the neighbors last September in the course of obtaining the building permit (collecting signatures), the architect said it was not a problem at all to remove the concrete walls and then build the foundation for our extension on our side.

A few weeks ago, however, he came up with a great idea. Now the partition walls are to remain, and our extension is to be built inside them. This makes it narrower (see picture). Motivation: Completely removing the partition walls poses too great a risk for the neighbors’ terraces (sliding soil). We understand that but find it annoying that almost a year after the initial planning one only now thinks about this.



Of course, we would prefer it if our living room did not taper, and have made the following proposals:

1) Saw off the partition walls above ground and build our extension on top of them. The neighbor could then, if he wants to build an extension in a few years, do the same => Allegedly not possible, especially because you cannot plan the statics of a hypothetical neighbor extension now.

2) Modified variant of 1): Saw off the partition walls above ground and build our extension slightly overhanging so that no force is exerted on the remaining partition wall. The neighbor could possibly do the same or saw off the wall (if our foundation is there, soil can no longer slip) => Allegedly not possible.

3) Saw off the partition walls vertically in the middle (that is the 16 cm) on our side => Allegedly not possible.

So currently it looks like the planning embedded above will be implemented. I would be interested in opinions on whether there really is no better way. Especially whether our suggestions outlined above are truly not feasible.

Thank you very much!

Hopefully this will not be the last occasion where the architect is wiser than the client :)

Hopefully this won't be the last occasion where the architect is smarter than the client :)

It's not about who is smarter or not. Rather, I have the impression that during the site visit, many nice things were quickly promised to me as the client (and to the neighbors). Then, until the last minute, no thoughts were given to the realization. And then the simplest solution was quickly proposed.

Therefore, I am interested in opinions on this solution or whether it could have been done better. We probably won't be able to change it now anyway.

And then quickly suggested the simplest solution.

No, the best one. The one that, in the best case, having 32 cm more width, would have cost you twice as much with technical extra work and notary fees. You received a professional solution for which you should be grateful.

No, the best. The one that, in the best case, would have been 32 cm wider would have cost you about twice as much with technical additional efforts and notary fees. You received a professional solution for which you should be grateful.

Thank you for the very helpful answer.

Is there a possibility that a professional could briefly outline what would be so complicated about the three options described above? I can't quite imagine the vertical cutting (point 3) myself (especially if it is reinforced concrete, as you would somehow have to cut around or past the reinforcement in an undefined way).

We were simply not given a choice beforehand ("For xxx € more, the extension would be yyy cm wider.").

Is there a possibility that a professional could briefly outline what would be so complicated about the three options described above?

Not really, not briefly. On weekdays and at the usual hourly rate, maybe, but for me it's too complex on a weekend with such beautiful weather. Be glad about my previous explanation – you can already "count yourself lucky" that I wrote so briefly (at the moment also from the notebook, I’m just not in the mood to stay indoors).