Unplanned retaining wall

Good evening everyone,
my wife and I finally found a suitable place to build last year after a long search.

The building plot is on a slope, or rather, the plot itself is relatively flat, but it is located on a kind of terrace. You can imagine it like a huge staircase and the house will be built on one of the steps.

We bought the property with the premise of having a specific house (adapted to our wishes) built by a certain construction company. So the company knew from the beginning what would be built where.

There was still a barn and an old residential building on the property. These buildings have now been demolished by 95%.
The first construction phase was labeled "completion of demolition."
Originally, we were told that a payment installment must be made only after the completion of a construction phase. So only what is really finished should be paid for. However, the small basement room of the house is still standing (the missing 5%) and yet we were already asked to pay the first installment.
Unfortunately, we did so immediately.

A soil survey was also recently carried out. Furthermore, the retaining wall that holds the property was examined more closely.
Now suddenly it is said that the construction company cannot guarantee that the wall will hold the house. They are advising us to build a new wall, which will cause very high unplanned costs.

Honestly, we feel a bit like we have been conned.

Shouldn’t such an inspection have been the very first thing to be done?
As laypersons, we builders cannot be expected to assess whether such a wall is sufficient or not. Who is to blame?

Under certain circumstances, the wall could cost as much again as the property (offer has not yet been received).

I look forward to your answers.

Kind regards,
Dennis + Anna

You bought the property externally, so not from the BU?

Correct, purchased from a private individual. But it was only through the [BU] that we came to the property. They practically offered it, hence the premise described above.

Hello,

I don't think you will be able to do much there, you bear the construction ground risk. And you cannot hold the construction company responsible for the dilapidated condition of the old retaining wall. You can search for sowiesokosten on Google.

I assume that your contract for work states that anything related to the property may cause on-site costs. Something along those lines. Have a look. Most construction companies always deal with the ground step by step. As a client, you are one of many, so the focus is unfortunately not always where you would like it to be. Ultimately, you are responsible for your building land yourself.

The soil survey report most likely led to the knowledge of the wall? Did anyone ever take care of the ground before? Look at it? Assess it?

I can understand the frustration, but legally you are unfortunately stuck because the property belongs to you :(

I would be surprised if I am wrong about that. I would also be grateful if an expert could argue it better.

The soil appraisal report most likely led to the knowledge of the wall?
Did anyone ever take care of the ground before? Looked at it? Assessed it?

No, the builder knew from the very beginning that the wall existed.

Originally, the property was larger. Since a semi-detached house is being built, the property was divided. With surveying, registration, and all that jazz...
On our side of the property, the wall looks much better than on the side of our future neighbors. On the neighbors' side, the wall consists of bare sandstone. On our side, the wall is mostly covered with concrete. At least, that's how it looks to me. It was also the neighbors who demanded a soil appraisal.

There is/was a certain person who works for the construction company and took care of us in the initial phase. As it has turned out by now, unfortunately, a notorious yes-man. For him, everything was always possible and no problem at all. The wall was no problem in his eyes either.

As I said, I feel slightly taken for a ride. But I don't necessarily want to start trouble just yet. There are still two other houses in the village that were built by the company. I have already talked to the owners. They have no complaints.

By the way: many thanks already for your answers. :)