Excavation beside foundation/underpinning

Hello!

I hope this is the appropriate subforum.

The following situation: Our neighbors are currently excavating about 0.50 - 0.6 m next to our garage to a depth of about 1.50 - 1.80 m. Our garage stands on strip foundations. I can't say exactly how deep they go, but I assume a maximum of 80 cm. No underpinning, shoring, or slope was created during the excavation. About 0.5 m next to our garage, it now goes vertically down at least 1.50 m deep.

According to my understanding, for example, of DIN 4123, if no further underpinning measures are carried out, excavation up to 2 m next to the garage may only be conducted to a maximum of 50 cm above the bottom edge of the foundations, that is about 30 cm deep. Only from a distance of 2 m onward may deeper excavation be done with a slope. Alternatively, appropriate underpinning sections would have to be professionally installed.

Are my concerns about the stability of the garage foundations justified, or am I mistaken? We have already spoken with the neighbors; they rely on their contractor. If my concerns are justified: What would be sensible next steps I can take to ensure the stability of the garage? The federal state is Hesse.

If anyone here has advice, I would be very grateful.

Oh dear, this will go wrong 99 percent of the time. Actually, a construction stop must be issued immediately and a proper plan for underpinning your foundations is necessary.

Here is a post from a terraced middle house that wanted to build a basement and undermined the neighboring houses without securing the foundations.

In your case, it sounds like it’s already too late.

Document everything and talk to the neighbor that the hole must be closed. And hope it doesn’t rain.

Look for the post "Reihenendhaus mit GÜ in Eigenregie bauen"

Search for the post Reihenendhaus mit GÜ in Eigenregie bauen

Yes, we will contact the building authority directly tomorrow.

What would otherwise be sensible next steps? Since the lateral pressing pressure is now missing or at least significantly reduced, the stability of the foundations could already be compromised, right? Does the building authority usually initiate a corresponding inspection, or do we have to cover the costs ourselves if that is even possible?

I found the article, but the topic has over 300 pages. Where exactly do I need to look?

The foundation doesn’t really care whether it has lateral clamping pressure or not. But the ground underneath the foundation is under vertical pressure from the garage, and now finds a path to escape sideways. And if the foundation then hangs in the air, the garage will tip sideways into the pit. The building authority will immediately shut down the construction measure. Your neighbor or his service provider must pay for the evidence, not you.

Hello,
It was similar for us: our double garage stands on the boundary. The neighbor built with a basement. The basement wall was also on the boundary with us. I hope you can imagine the problem...A structural engineer calculated an underpinning: first, a 4m deep hole was dug exactly on the boundary. The garage was basically standing on a cliff. Then, in about 8 sections each about 1m wide, the earth under our strip foundations was dug out and secured with a concrete wall. Our garage now stands on a subsequently built 4m deep wall...
It was quite delicate. We documented everything. The whole operation was a year ago. Until today everything is fine. No cracks or similar.
In our residential area many dig very close to the boundary - the plots are very small. Every garage stands on the boundary. So far I’ve never heard of any problems.
Just ask at the building authority and let me know here. I am very curious myself...