ᐅ Retaining wall with strip foundation and cascading formwork blocks
Created on: 30 May 2018 08:45
T
tim2111Hello everyone,
I have the following project in my garden:
There is a slight slope across our property, approximately 1.20 meters (4 feet) from the front right to the back left. To nearly level this out, I would like to build a retaining wall along the right side and the back of the property, fill it from the inside, and thereby raise the ground level. In this region, retaining walls up to 1 meter (3.3 feet) high can be built without a building permit / planning permission, so I want to keep just under this height.
At first, I planned to hire a landscaping contractor and use L-shaped steel anchors for the wall. However, based on the quotes I received and because I also want to install a double-wire mesh fence on top of the retaining wall, I am now considering doing the project myself.
I have already done quite a bit of reading and research and plan to proceed as follows:
- Excavation and installation of a strip foundation along the property boundary, approximately 80 cm (31 inches) deep to frost-free depth. The total length is about 30 meters (98 feet) on the right side and 25 meters (82 feet) at the back.
- Building the wall with formwork blocks and filling them with concrete including reinforcement.
- From a structural point of view, this should be feasible for a maximum height of 1 meter (3.3 feet) without special load requirements (no traffic or similar) and an 80 cm (31 inches) strip foundation, based on what I have read. Would you have any concerns here?
- After placing the formwork blocks but before pouring the concrete, I would set the fence posts directly in the formwork blocks and cast them in.
How should I handle the foundation considering the slope? My idea is to step the foundation in 20 cm (8 inches) increments—the height of one formwork block—so that at the front end of the property the strip foundation is at ground level (and I would cast the fence directly there). Then, as the terrain slopes downward, the strip foundation would step down in 20 cm increments following the natural slope. Accordingly, I would install the 20 cm high formwork blocks in steps with the descending terrain so that in the end I have a level wall. For this, I would need to cascade the foundation stepwise. How would you approach this? The soil is very firm and clayey, so I plan to pour the strip foundation directly into the excavated ground and only form (shape) the top few centimeters to create a clean finish.
What do you think?
Looking forward to your tips and advice!
I have the following project in my garden:
There is a slight slope across our property, approximately 1.20 meters (4 feet) from the front right to the back left. To nearly level this out, I would like to build a retaining wall along the right side and the back of the property, fill it from the inside, and thereby raise the ground level. In this region, retaining walls up to 1 meter (3.3 feet) high can be built without a building permit / planning permission, so I want to keep just under this height.
At first, I planned to hire a landscaping contractor and use L-shaped steel anchors for the wall. However, based on the quotes I received and because I also want to install a double-wire mesh fence on top of the retaining wall, I am now considering doing the project myself.
I have already done quite a bit of reading and research and plan to proceed as follows:
- Excavation and installation of a strip foundation along the property boundary, approximately 80 cm (31 inches) deep to frost-free depth. The total length is about 30 meters (98 feet) on the right side and 25 meters (82 feet) at the back.
- Building the wall with formwork blocks and filling them with concrete including reinforcement.
- From a structural point of view, this should be feasible for a maximum height of 1 meter (3.3 feet) without special load requirements (no traffic or similar) and an 80 cm (31 inches) strip foundation, based on what I have read. Would you have any concerns here?
- After placing the formwork blocks but before pouring the concrete, I would set the fence posts directly in the formwork blocks and cast them in.
How should I handle the foundation considering the slope? My idea is to step the foundation in 20 cm (8 inches) increments—the height of one formwork block—so that at the front end of the property the strip foundation is at ground level (and I would cast the fence directly there). Then, as the terrain slopes downward, the strip foundation would step down in 20 cm increments following the natural slope. Accordingly, I would install the 20 cm high formwork blocks in steps with the descending terrain so that in the end I have a level wall. For this, I would need to cascade the foundation stepwise. How would you approach this? The soil is very firm and clayey, so I plan to pour the strip foundation directly into the excavated ground and only form (shape) the top few centimeters to create a clean finish.
What do you think?
Looking forward to your tips and advice!
H
HilfeHilfe30 May 2018 23:23Hello, I did it the same way as you. I even mixed the concrete myself using a mixer. The only difference was the fence. Here, we have thuja hedges because the neighbor attached their fence to the wall.
K
Knallkörper30 May 2018 23:42Stepping the foundation is definitely correct. This should be possible with a timber formwork.
I would also include reinforcement in the strip foundation. Vertical rebar that extends 15cm (6 inches) above the top and ties into the first row of concrete blocks. This way, you transfer the torque from the earth pressure through the wall height into the foundation.
You could also anchor the fence posts onto the finished wall instead of embedding them in concrete.
I would also include reinforcement in the strip foundation. Vertical rebar that extends 15cm (6 inches) above the top and ties into the first row of concrete blocks. This way, you transfer the torque from the earth pressure through the wall height into the foundation.
You could also anchor the fence posts onto the finished wall instead of embedding them in concrete.
Great, thanks already for your answers, which are of course very helpful!
Why would you rather bolt the fence posts on? I had thought about it, but since the fence posts are usually designed for embedding in concrete and the bolting option is an "extra," I thought that since I’m working on it anyway… Or do you see an advantage in that?
Thanks again to all of you!
Knallkörper schrieb:
Stepping the foundation is definitely correct. It should be possible with a timber formwork.
I would also install reinforcement in the strip footing. Vertical rebar protruding 15cm (6 inches) at the top and tying into the first layer of concrete blocks. This way, you transfer the torsion caused by earth pressure through the wall height into the foundation.
You could also fix the fence posts onto the finished wall by bolting them instead of casting them in concrete.
Why would you rather bolt the fence posts on? I had thought about it, but since the fence posts are usually designed for embedding in concrete and the bolting option is an "extra," I thought that since I’m working on it anyway… Or do you see an advantage in that?
Thanks again to all of you!
Domski schrieb:
The version with doweling allows for better alignment. You can use shims to set those precisely vertical. When pouring concrete, that only works to a limited extent, and set is set. Good point, thanks!
What do you think about pouring concrete? Because of the length of the entire foundation, I won’t be able to pour it all at once. Is that a problem? What is the best way to handle the “joints” — bevel and roughen the edges, then pour against them at the next opportunity?
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