ᐅ Berlin-style temporary retaining structure for securing the excavation pit
Created on: 21 Sep 2023 10:54
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Bayernbors
Hello everyone,
There are several issues with the excavation at our construction project. The general contractor (GC) says the planned house is large (2 semi-detached houses, each 11 by 7 meters (36 by 23 feet)) and the plot is small (~450 m² (4844 ft²)), which brings some technical challenges.
The work on the excavation started with the demolition of the old house, as it already had a basement.
The worst part is that we discovered all these problems gradually, not as originally planned:
1) First, it turned out that the edges of the excavation were unstable, requiring support for the crane, so a crane foundation was built.
2) Secondly, it was found that the plot was still too small for the crane, and a permit was needed to place the crane partially on the sidewalk.
The first two steps were completed by the end of June, and then work was completely halted (except for the crane setup).
At the end of August, my new neighbors contacted me and were concerned because they saw that the sides of the excavation were slipping more and more, causing the excavation to slope toward their property and compromising the slope’s stability.
At this point, the GC said they had already discussed this issue with the relevant authorities. They suggested increasing the slope of the excavation, but this proposal was rejected because it would affect the sidewalk.
The only remaining solution was then to provide a bond to secure the stability of the sidewalk.
After an additional geotechnical investigation, it was determined that sheet piling is required on all sides, not just along the sidewalk.
My questions are:
Does all this make sense?
Is it normal to discover these issues so late? Does it really take about three months to reach this conclusion? Should I hold the GC accountable for these delays?
Note: At the end of June, I agreed with the GC that the house should be completed by the end of February 2024, as our contract states: “The contractor commits to delivering the project ready for occupancy within 8 months from the start of excavation, weather permitting.”
Finally, how much more time should I expect to complete this Berliner trench sheet pile installation and finally begin construction?
I have read online that the costs could be several tens of thousands— is that realistic?
Thank you very much.
Best regards
There are several issues with the excavation at our construction project. The general contractor (GC) says the planned house is large (2 semi-detached houses, each 11 by 7 meters (36 by 23 feet)) and the plot is small (~450 m² (4844 ft²)), which brings some technical challenges.
The work on the excavation started with the demolition of the old house, as it already had a basement.
The worst part is that we discovered all these problems gradually, not as originally planned:
1) First, it turned out that the edges of the excavation were unstable, requiring support for the crane, so a crane foundation was built.
2) Secondly, it was found that the plot was still too small for the crane, and a permit was needed to place the crane partially on the sidewalk.
The first two steps were completed by the end of June, and then work was completely halted (except for the crane setup).
At the end of August, my new neighbors contacted me and were concerned because they saw that the sides of the excavation were slipping more and more, causing the excavation to slope toward their property and compromising the slope’s stability.
At this point, the GC said they had already discussed this issue with the relevant authorities. They suggested increasing the slope of the excavation, but this proposal was rejected because it would affect the sidewalk.
The only remaining solution was then to provide a bond to secure the stability of the sidewalk.
After an additional geotechnical investigation, it was determined that sheet piling is required on all sides, not just along the sidewalk.
My questions are:
Does all this make sense?
Is it normal to discover these issues so late? Does it really take about three months to reach this conclusion? Should I hold the GC accountable for these delays?
Note: At the end of June, I agreed with the GC that the house should be completed by the end of February 2024, as our contract states: “The contractor commits to delivering the project ready for occupancy within 8 months from the start of excavation, weather permitting.”
Finally, how much more time should I expect to complete this Berliner trench sheet pile installation and finally begin construction?
I have read online that the costs could be several tens of thousands— is that realistic?
Thank you very much.
Best regards
So, I also don’t like the slope next to number 18, or rather, it shouldn’t stay like that.
The slope near the garage currently looks unproblematic.
Am I correct in assuming that the new building will have a basement? That means the excavation will need to be extended further.
In general, you can calculate yourself where you will need shoring. Outer edge of the foundation slab plus 1 meter (3 feet) working space, then slope it back at a 60-degree angle. At the top, there should be at least 1 meter (3 feet) of soil left in place. If this is not possible, then shoring is necessary.
Based on the site plan, I think it will be tight near the street on the west side and towards house number 18.
The slope near the garage currently looks unproblematic.
Am I correct in assuming that the new building will have a basement? That means the excavation will need to be extended further.
In general, you can calculate yourself where you will need shoring. Outer edge of the foundation slab plus 1 meter (3 feet) working space, then slope it back at a 60-degree angle. At the top, there should be at least 1 meter (3 feet) of soil left in place. If this is not possible, then shoring is necessary.
Based on the site plan, I think it will be tight near the street on the west side and towards house number 18.
Bayernbors schrieb:
I don’t think this was done. I asked the architect and the general contractor once at the beginning, but the architect said it was not necessary at that time, and I failed to follow up on it. An expert report on a building plot that will soon be excavated would indeed have limited usefulness, but securing the adjacent neighbor’s house should still have been a high priority.
Bayernbors schrieb:
Yes, unfortunately I don’t have plans for the excavation pit. The shoring is also not yet planned. I am still waiting for that to be done. […] The plan was to complete the excavation pit together with the demolition of the old house with basement without waiting. Due to poor planning (or completely missing planning), it became clear during the work that some additional measures would have to be carried out that were not planned, so the excavation was stopped halfway through. It still hasn’t become clear to me in the slightest whether the excavation pit is supposed to be enlarged to build a new basement in the new position beneath the duplex, or if the situation is just going to remain as a reminder of your shrugging it off. Everyone knows as surely as the sun rises that missing planning inevitably causes surprises (although apparently not every builder/contractor understands this). Are you even aware that you are fully liable, including criminally, for any (in)action of your incompetent team?
Bayernbors schrieb:
Sorry, that’s my mistake. I didn’t understand why “bond” was mentioned here, then I realized I had mistakenly used that term in my first post when I meant “shoring system” — that is, the Berlin-style shoring. *eye roll* *still don’t get it* I don’t see what Friedrich Schiller has to do with all this nonsense. I assumed that you, among other things, had provided a deposit (security) for possible damages to the sidewalk.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
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Bayernbors28 Sep 2023 14:12Cronos86 schrieb:
I also don’t like the slope next to number 18, or rather it shouldn’t stay like that. I didn’t like it either, but the general contractor now says we have written confirmation from the local authority that the current situation is not dangerous.
Cronos86 schrieb:
Am I right in assuming that the new building will have a basement? Does that mean the excavation pit needs to be enlarged? 11ant schrieb:
It’s still not clear to me at all, even for a small amount, whether the excavation pit will be stretched to make room for a new basement under the semi-detached house in the new position. Yes, we will have a basement. The excavation pit will be enlarged to the dimensions of the house plus 1 meter (i.e., it will be 12 by 15 meters (39 by 49 feet)) and will be 3 meters (10 feet) deep.
We hope to start the basement slab next week.
Cronos86 schrieb:
Looking at the site plan, I think it will be tight next to the street on the west side and also near house number 18. Exactly, it’s very tight on the east and west sides, but according to the soil report, we have to construct the basement slab around the entire basement. So this will be done on the north side (i.e., the garage side) as well as the south side where the crane will be.
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NewHouseAppear28 Sep 2023 16:02This is supposed to start next week, and you don’t even have a cost estimate yet? Fully shoring the excavation pit is not a small task and can become quite expensive.
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Bayernbors10 Nov 2023 20:03Just a quick update:
It took some time to finally complete. The experts said that we only need it on 2 sides (street sides). It cost about 35,000.
Now the excavation is finished, and work in the basement is starting.
Thanks for your advice.
It took some time to finally complete. The experts said that we only need it on 2 sides (street sides). It cost about 35,000.
Now the excavation is finished, and work in the basement is starting.
Thanks for your advice.
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