R
Ratsuchender2513 Sep 2025 19:00Hello!
I hope this is the right subforum.
Here is the situation: Our neighbors are currently excavating about 0.50 - 0.6 m (20 - 24 inches) away from our garage to a depth of approximately 1.50 - 1.80 m (59 - 71 inches). Our garage is built on strip foundations. I don’t know the exact depth of these, but I assume they extend to a maximum of 80 cm (31 inches). No underpinning, shoring, or battering/sloping was done during the excavation. About 0.5 m (20 inches) from our garage, the ground is now excavated straight down to at least 1.50 m (59 inches) depth.
According to my understanding of standards like DIN 4123, if no additional underpinning measures are taken, excavation up to 2 m (6.5 ft) next to the garage should only go to a maximum of 50 cm (20 inches) above the foundation base, which is about 30 cm (12 inches) deep. Only beyond 2 m (6.5 ft) distance can excavation be carried out deeper with a proper slope or batter. Otherwise, appropriate section-by-section underpinning should be carried out professionally.
Are my concerns about the structural stability of the garage foundations justified, or am I mistaken? We have already spoken with the neighbors, but they rely on their contractor. If my concerns are valid, what would be reasonable next steps I can take to ensure the stability of the garage? The location is the federal state of Hesse.
I would really appreciate any advice anyone can offer here.
I hope this is the right subforum.
Here is the situation: Our neighbors are currently excavating about 0.50 - 0.6 m (20 - 24 inches) away from our garage to a depth of approximately 1.50 - 1.80 m (59 - 71 inches). Our garage is built on strip foundations. I don’t know the exact depth of these, but I assume they extend to a maximum of 80 cm (31 inches). No underpinning, shoring, or battering/sloping was done during the excavation. About 0.5 m (20 inches) from our garage, the ground is now excavated straight down to at least 1.50 m (59 inches) depth.
According to my understanding of standards like DIN 4123, if no additional underpinning measures are taken, excavation up to 2 m (6.5 ft) next to the garage should only go to a maximum of 50 cm (20 inches) above the foundation base, which is about 30 cm (12 inches) deep. Only beyond 2 m (6.5 ft) distance can excavation be carried out deeper with a proper slope or batter. Otherwise, appropriate section-by-section underpinning should be carried out professionally.
Are my concerns about the structural stability of the garage foundations justified, or am I mistaken? We have already spoken with the neighbors, but they rely on their contractor. If my concerns are valid, what would be reasonable next steps I can take to ensure the stability of the garage? The location is the federal state of Hesse.
I would really appreciate any advice anyone can offer here.
Oh no, this will fail 99 percent of the time. Actually, construction should be stopped immediately and a proper plan for underpinning your foundations needs to be put in place.
There is a post about a terraced middle house that wanted to build a basement and ended up undermining the neighboring houses without securing the foundations.
In your case, it sounds like it might already be too late.
Document everything and talk to your neighbor to have the hole filled. And hope it doesn’t rain.
Look for the post "Terraced end house with underpinning done independently."
There is a post about a terraced middle house that wanted to build a basement and ended up undermining the neighboring houses without securing the foundations.
In your case, it sounds like it might already be too late.
Document everything and talk to your neighbor to have the hole filled. And hope it doesn’t rain.
Look for the post "Terraced end house with underpinning done independently."
R
Ratsuchender2514 Sep 2025 07:04Thank you!
Yes, we will contact the building authority directly tomorrow.
What would be sensible next steps otherwise? Since the lateral pressure is now missing or at least significantly reduced, the stability of the foundations could already be compromised, right? Does the building authority usually arrange for an appropriate inspection in such cases, or would we have to cover the costs ourselves if this is even possible?
I found the post, but the topic has over 300 pages. Where exactly should I look?
Yes, we will contact the building authority directly tomorrow.
What would be sensible next steps otherwise? Since the lateral pressure is now missing or at least significantly reduced, the stability of the foundations could already be compromised, right? Does the building authority usually arrange for an appropriate inspection in such cases, or would we have to cover the costs ourselves if this is even possible?
I found the post, but the topic has over 300 pages. Where exactly should I look?
A
ajokr202514 Sep 2025 08:39The foundation itself is relatively unaffected by lateral pressure. However, the soil beneath the foundation is subjected to vertical pressure from the garage and now finds a way to escape sideways. If the foundation then becomes unsupported, the garage will tilt sideways into the excavation.
The building authority will immediately halt the construction work. Your neighbor or their contractor is responsible for covering the costs of any required assessments, not you.
The building authority will immediately halt the construction work. Your neighbor or their contractor is responsible for covering the costs of any required assessments, not you.
Hello,
We had a similar situation: our double garage is built right on the property line. The neighbor constructed a basement, and their basement wall was also directly on the boundary with us. I hope you can imagine the challenge this caused... A structural engineer designed an underpinning solution: first, a 4-meter (13 feet) deep trench was dug exactly along the boundary. The garage was basically standing on a cliff. Then, in about eight sections around 1 meter (3 feet) wide each, the soil beneath our strip foundations was excavated and reinforced with a concrete wall. Our garage now rests on a newly constructed 4-meter (13 feet) deep wall...
It was quite delicate. We documented everything. This whole process happened a year ago. So far, everything is fine—no cracks or similar issues.
In our residential area, many people dig very close to the boundary lines because the plots are very small. Every garage is built on the boundary. Until now, I have never heard of any problems.
Just check with the local building authority (building permit / planning permission office) and let us know. I’m very curious myself...
We had a similar situation: our double garage is built right on the property line. The neighbor constructed a basement, and their basement wall was also directly on the boundary with us. I hope you can imagine the challenge this caused... A structural engineer designed an underpinning solution: first, a 4-meter (13 feet) deep trench was dug exactly along the boundary. The garage was basically standing on a cliff. Then, in about eight sections around 1 meter (3 feet) wide each, the soil beneath our strip foundations was excavated and reinforced with a concrete wall. Our garage now rests on a newly constructed 4-meter (13 feet) deep wall...
It was quite delicate. We documented everything. This whole process happened a year ago. So far, everything is fine—no cracks or similar issues.
In our residential area, many people dig very close to the boundary lines because the plots are very small. Every garage is built on the boundary. Until now, I have never heard of any problems.
Just check with the local building authority (building permit / planning permission office) and let us know. I’m very curious myself...
R
Ratsuchender2514 Sep 2025 08:50ajokr2025 schrieb:
The foundation doesn’t really care whether it experiences lateral pressure or not. But the soil beneath the foundation is under vertical pressure from the garage and will then find a way to move sideways. If the foundation ends up suspended in the air, the garage will tip sideways into the excavation.
The building authority will immediately stop the construction work. Your neighbor or their contractor has to pay for any required proof, not you. How quickly does something like this usually happen? Of course, it depends on the local authority, but is it possible to expect an inspection or action on the same day if you call them first thing in the morning? The pool will probably be installed within the next few days, and then you won’t be able to see anything anymore. Soil just poured loosely into the gap between the pool and the excavation would not restore the lateral pressure, and the pool likely can’t support that pressure.
Kati2022 schrieb:
Hello,
We had a similar situation: our double garage sits right on the property boundary. The neighbor built a basement. Their basement wall was also on the boundary with us. I’m sure you can imagine the problem... A structural engineer calculated underpinning: first, a 4m (13 feet) deep hole was dug exactly on the boundary. So the garage was basically sitting on a cliff. Then, in about eight sections, each roughly 1m (3 feet) wide, soil was excavated under our strip foundations and secured with a concrete wall. Now our garage rests on a subsequently constructed 4m (13 feet) deep wall...
It was quite delicate. We documented everything. The entire process happened a year ago. So far, everything is fine. No cracks or anything like that.
In our neighborhood, 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 your local building department and let us know. I’m very curious myself... This definitely sounds like someone with the right expertise gave it careful thought. Unfortunately, our neighbors have no such planning or structural calculation. I will update once I know more.
Similar topics