ᐅ Retaining wall for the retaining wall!? Do you have any ideas?
Created on: 14 Mar 2023 09:06
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Hausbau75
Good morning everyone,
First of all, a friendly hello! This is my first post here, and I hope I’m in the right place.
Last week, we had our “greenfield” meeting on the property, which means the civil engineer, basement builder, and house builder were all present. Unfortunately, we discovered that the elevation level relative to the neighbors’ retaining walls is not quite as it was supposed to be in theory. We are closer to the walls and not as high as expected. You could wonder how this happened, but that won’t help—I need solutions because the situation is what it is.
I’ve uploaded two pictures that clearly show what it’s about. I also made some colored markings to get a better overview.
Regarding the issue:
We bought the house together with a rather large carport that serves as a porch roof and storage area (the building permit / planning permission has been approved, and the house is already scheduled for production, so no changes are possible anymore). Above the carport, there is a wall made of planter stones (visible on the right side of the first picture). Along the entire length, the civil engineer will now build a retaining wall, ensuring that neither the carport nor the existing wall will be affected—essentially a retaining wall for the retaining wall. This will be done before the house and carport are built, otherwise it wouldn’t make sense.
On the left side of the picture, you can see a retaining wall made of L-shaped concrete blocks about 2m (6.5 feet) high. You can see from the photos that the civil engineer has already excavated earth up to about 2m (6.5 feet) before this wall. He hasn’t dared to go closer yet. Another problem in this area is two large roots that almost certainly extend beneath the foundation of the L-block wall.
The civil engineer is now understandably worried that if he works closer to the wall and cuts these roots (he does not want to remove them because he and we believe they extend under the L-blocks), the roots will die, which could eventually cause the L-blocks to settle.
As you can see, we definitely need more maneuvering space to be able to get a vehicle under the carport and also back out again. Currently, there is about 2m (6.5 feet) to the edge of the house, which is definitely too little space. Leaving it as is would also waste too much space on the property. While we want to plant something along the wall, a 2m (6.5 feet) wide strip is too much.
Now we need your advice. Do you have any ideas on how to support this L-block wall if these two roots need to be removed?
We have time to proceed this way—the house construction will take the entire year and certainly the driveway won’t be paved immediately after that, probably not even next year. Nevertheless, I would appreciate your opinions and ideas because it is important to us to do this correctly, well, and safely. Money is naturally tighter than it might have been a few years ago, so we are also interested in your cost-effective suggestions.
Thank you very much for any ideas…
Best regards,
Paul
First of all, a friendly hello! This is my first post here, and I hope I’m in the right place.
Last week, we had our “greenfield” meeting on the property, which means the civil engineer, basement builder, and house builder were all present. Unfortunately, we discovered that the elevation level relative to the neighbors’ retaining walls is not quite as it was supposed to be in theory. We are closer to the walls and not as high as expected. You could wonder how this happened, but that won’t help—I need solutions because the situation is what it is.
I’ve uploaded two pictures that clearly show what it’s about. I also made some colored markings to get a better overview.
Regarding the issue:
We bought the house together with a rather large carport that serves as a porch roof and storage area (the building permit / planning permission has been approved, and the house is already scheduled for production, so no changes are possible anymore). Above the carport, there is a wall made of planter stones (visible on the right side of the first picture). Along the entire length, the civil engineer will now build a retaining wall, ensuring that neither the carport nor the existing wall will be affected—essentially a retaining wall for the retaining wall. This will be done before the house and carport are built, otherwise it wouldn’t make sense.
On the left side of the picture, you can see a retaining wall made of L-shaped concrete blocks about 2m (6.5 feet) high. You can see from the photos that the civil engineer has already excavated earth up to about 2m (6.5 feet) before this wall. He hasn’t dared to go closer yet. Another problem in this area is two large roots that almost certainly extend beneath the foundation of the L-block wall.
The civil engineer is now understandably worried that if he works closer to the wall and cuts these roots (he does not want to remove them because he and we believe they extend under the L-blocks), the roots will die, which could eventually cause the L-blocks to settle.
As you can see, we definitely need more maneuvering space to be able to get a vehicle under the carport and also back out again. Currently, there is about 2m (6.5 feet) to the edge of the house, which is definitely too little space. Leaving it as is would also waste too much space on the property. While we want to plant something along the wall, a 2m (6.5 feet) wide strip is too much.
Now we need your advice. Do you have any ideas on how to support this L-block wall if these two roots need to be removed?
We have time to proceed this way—the house construction will take the entire year and certainly the driveway won’t be paved immediately after that, probably not even next year. Nevertheless, I would appreciate your opinions and ideas because it is important to us to do this correctly, well, and safely. Money is naturally tighter than it might have been a few years ago, so we are also interested in your cost-effective suggestions.
Thank you very much for any ideas…
Best regards,
Paul
C
Costruttrice14 Mar 2023 10:22haydee schrieb:
I can’t find the pictures anymore. We also had to dig deeper than the old retaining wall extended. The wall was divided into 1.5 m (5 feet) sections:
Dig 1.5 m (5 feet) and pour concrete, leave 3 m (10 feet) standing, dig 1.5 m (5 feet) and pour concrete, leave 3 m (10 feet) standing, and so on.
1.5 m (5 feet) already poured, 1.5 m (5 feet) dug, 1.5 m (5 feet) left standing, etc.
3 m (10 feet) already poured, 1.5 m (5 feet) dug, and so on.
This way, a small retaining wall was built in front of the old one.
This was determined by the foundation contractor, the architect, and the expert after a brief consultation with the structural engineer and geologist. This is how it was done in our case after coordination between the foundation contractor and the structural engineer. Unfortunately, I don’t have photos where this is clearly visible. But if you search for “underpinning,” you will find examples. I quickly attached a photo from the internet showing the principle. As @haydee describes, the wall to be secured is divided into individual sections. You dig out the first and third sections, leaving the middle one standing. Then, the first and third sections are poured (or built up with masonry, depending on the situation) up to the existing wall. Once this has cured, work moves to the section that was left standing, which is then excavated, and so on.
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hanghaus202314 Mar 2023 10:32The L-shaped concrete blocks are at least frost-protected, with foundations about 80 cm (31 inches) below the finished ground level. I suspect that the support of the L-block extends into the neighboring property. If you want to dig one meter (3 feet) deeper, the foundations of the retaining wall will also need to be lowered by one meter (3 feet). This can be done step by step, as mentioned before. Do you know why the excavator initially said to stop at this point and not go further? That will result in a significant additional cost. If you want to proceed this way, I strongly recommend handling it before the main construction begins, otherwise it will get even more expensive.
Show us your plans. Where is the driveway located, and why is the carport placed in that corner? It can't get more expensive than that, can it?
Show us your plans. Where is the driveway located, and why is the carport placed in that corner? It can't get more expensive than that, can it?
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hanghaus202314 Mar 2023 10:37Get a copy of the neighbor’s retaining wall plans. Using L-shaped blocks may make underpinning more difficult in some cases.
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Costruttrice14 Mar 2023 10:41hanghaus2023 schrieb:
That will be a substantial additional cost.
If you want to do it that way, I can only advise you to take care of it before starting construction. Otherwise, it will become even more expensive. I can confirm both points.
Focus on this thoroughly now and have it done right away as a priority!
H
hanghaus202314 Mar 2023 10:48Be sure to consult a structural engineer for the design of the underpinning beforehand. The attached image is very optimistic. Usually, the sections are only 1.25 m (4 feet) long. Try searching for BGBau foundations next to footings and underpinning.
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Hausbau7514 Mar 2023 10:54@Costruttrice
Thank you for your explanation, I think I understand it now. For me, it’s quite different... We don’t yet have a price for the right side wall behind the carport, but it would have to be done the same way there... It sounded so easy at the construction site...
Let’s continue with the L-block wall on the left side, now that we have a solution for the wall. But how do you see the issue with the roots? If we grind them away, they will eventually die off. Could it then really happen that the L-blocks don’t tip forward but instead settle downward?
@hanghaus2023
I still need to obscure the site plan a bit, I’ll provide it later...
There are no documents for the existing retaining wall, we already asked. It was built before the current owners moved in.
Thank you for your explanation, I think I understand it now. For me, it’s quite different... We don’t yet have a price for the right side wall behind the carport, but it would have to be done the same way there... It sounded so easy at the construction site...
Let’s continue with the L-block wall on the left side, now that we have a solution for the wall. But how do you see the issue with the roots? If we grind them away, they will eventually die off. Could it then really happen that the L-blocks don’t tip forward but instead settle downward?
@hanghaus2023
I still need to obscure the site plan a bit, I’ll provide it later...
There are no documents for the existing retaining wall, we already asked. It was built before the current owners moved in.
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