Hello and thank you for reading.
We are currently in the middle of building our house. The basement (garden level) is already completed, and starting the week after next, we will begin backfilling. In the process, we realized we forgot an important detail in the planning, and I am now looking for a good solution.
Specifically, we are building on a sloped plot of land (with a fantastic view). The land slopes down from the street at the front into the valley. The street itself is on a slope, so we will be building higher than the neighbors next to us. For various reasons, this results in a boundary construction. While the neighbor’s garage driveway slopes down about 100cm (40 inches) from the street, our driveway rises about 50cm (20 inches) from the street.
This means that our garage entrance is up to 150cm (60 inches) higher than the neighbor’s at the property line. Therefore, we need to build a retaining wall directly at the boundary. The neighbor already has a wall at the boundary, but naturally, it is only as high as their driveway (our land was previously at a lower level). Our building permit for the retaining wall has been approved, but the exact type of wall has not yet been decided.
The retaining wall will be 6 meters (20 feet) long in total; it starts at the same height as the neighbor’s wall and rises slightly in height, while theirs slopes down:
-----------------------------------
(higher) Street (lower)
-----------------------------------
Same height | Same height
..................... | v
50cm (20 in) higher | 100cm (40 in) lower
-----------------|--------------
Our house | Neighbor’s house
..................... ^Retaining wall
The best solution would probably be to simply use concrete L-shaped blocks. However, we are facing delivery time issues with these. L-blocks apparently take about three weeks to deliver—and unfortunately, we don’t have that much time. I have not yet found a concrete plant that has stock available for immediate delivery.
Another idea is to use gabions (wire cages filled with stones). We personally find this option more visually appealing. If 30cm (12 in) wide gabions are sufficient, the slightly narrower driveway to the double garage would also not be a problem.
Does anyone have experience using gabions as retaining walls?
Since our driveway will be directly adjacent, the soil behind the gabions would need to be compacted. I have researched this already. Some say this is absolutely crazy because compaction can cause the gabions to bulge and become a hazard. Others say that compacting the soil in layers (while simultaneously filling the gabions with stones) is not a problem.
What is correct? Can 30cm (12 in) wide gabions be used as a retaining wall with the front yard/driveway soil compacted behind them without the gabions bulging? Do the gabions need a concrete foundation, possibly reinforced with embedded metal pipes, or is a 40cm (16 in) gravel bed sufficient (I have found contradictory information on this as well)? Is there a particular type of stone that works especially well for this application?
I appreciate any advice. Please no questions about why we are only dealing with this now. The wall was actually overlooked during planning. Although it was included in the building permit, we never requested it from any contractor, so it only became apparent just before Christmas that it would actually need to be built in January. We have an architect, but only for the house itself, not yet for the exterior landscaping. Hence (and due to holiday/vacation schedules), I am reaching out to experts here.
Best regards and many thanks,
tabaluga
We are currently in the middle of building our house. The basement (garden level) is already completed, and starting the week after next, we will begin backfilling. In the process, we realized we forgot an important detail in the planning, and I am now looking for a good solution.
Specifically, we are building on a sloped plot of land (with a fantastic view). The land slopes down from the street at the front into the valley. The street itself is on a slope, so we will be building higher than the neighbors next to us. For various reasons, this results in a boundary construction. While the neighbor’s garage driveway slopes down about 100cm (40 inches) from the street, our driveway rises about 50cm (20 inches) from the street.
This means that our garage entrance is up to 150cm (60 inches) higher than the neighbor’s at the property line. Therefore, we need to build a retaining wall directly at the boundary. The neighbor already has a wall at the boundary, but naturally, it is only as high as their driveway (our land was previously at a lower level). Our building permit for the retaining wall has been approved, but the exact type of wall has not yet been decided.
The retaining wall will be 6 meters (20 feet) long in total; it starts at the same height as the neighbor’s wall and rises slightly in height, while theirs slopes down:
-----------------------------------
(higher) Street (lower)
-----------------------------------
Same height | Same height
..................... | v
50cm (20 in) higher | 100cm (40 in) lower
-----------------|--------------
Our house | Neighbor’s house
..................... ^Retaining wall
The best solution would probably be to simply use concrete L-shaped blocks. However, we are facing delivery time issues with these. L-blocks apparently take about three weeks to deliver—and unfortunately, we don’t have that much time. I have not yet found a concrete plant that has stock available for immediate delivery.
Another idea is to use gabions (wire cages filled with stones). We personally find this option more visually appealing. If 30cm (12 in) wide gabions are sufficient, the slightly narrower driveway to the double garage would also not be a problem.
Does anyone have experience using gabions as retaining walls?
Since our driveway will be directly adjacent, the soil behind the gabions would need to be compacted. I have researched this already. Some say this is absolutely crazy because compaction can cause the gabions to bulge and become a hazard. Others say that compacting the soil in layers (while simultaneously filling the gabions with stones) is not a problem.
What is correct? Can 30cm (12 in) wide gabions be used as a retaining wall with the front yard/driveway soil compacted behind them without the gabions bulging? Do the gabions need a concrete foundation, possibly reinforced with embedded metal pipes, or is a 40cm (16 in) gravel bed sufficient (I have found contradictory information on this as well)? Is there a particular type of stone that works especially well for this application?
I appreciate any advice. Please no questions about why we are only dealing with this now. The wall was actually overlooked during planning. Although it was included in the building permit, we never requested it from any contractor, so it only became apparent just before Christmas that it would actually need to be built in January. We have an architect, but only for the house itself, not yet for the exterior landscaping. Hence (and due to holiday/vacation schedules), I am reaching out to experts here.
Best regards and many thanks,
tabaluga
To begin with: Gabions are purely decorative or visual elements that serve as screens against wind and, in water management areas, as protection against sand-laden winds and similar conditions. They have never been intended as retaining walls.
The structural demands for a freestanding gabion measuring 150 cm (59 inches) high and 30 cm (12 inches) wide are considerable. A foundation with appropriate drainage must be constructed according to the specific requirements to ensure the gabions stand firmly and stably and do not sink or shift at any corner or side. For each linear meter, two supports must be concreted in place at the center (e.g., steel pipes or steel posts) that should be about 10 cm (4 inches) shorter than the height of the gabion so they remain invisible. Gabions over 100 cm (39 inches) high are not stable on their own and there is a risk of tipping over.
The steel mesh cages (usually supplied as kits) must be filled by hand; post-compaction is not possible because they are not designed for this, and the connectors between the sidewalls are also not intended for this purpose.
The infilled soil would push the gabions outward. Furthermore, as I understand it, you might not even see the gabions because your property is situated higher than that of your neighbors, correct?
Regarding gabions, I would recommend contacting the company Unger and Bultmann in Ahrensburg; they can provide very good advice and might have a suitable solution. Keep in mind, however, that gabions usually have a delivery time of about one week plus assembly time. Filling them is very labor-intensive, and the foundation curing time should not be underestimated.
L-shaped retaining walls (angle walls) are the best choice. There are many manufacturers in your area, such as Siemsen in Schwarzenbek, Rekers Concrete Works in Spelle, Westerwelle in Herford, Seling Concrete in Melle, possibly Hacon in Rellingen, and depending on their flexibility, Berding Concrete.
For the load case of car traffic (5 kN/m² or 104 psf), these walls are usually kept in stock, at least this is my experience with Siemsen and Westerwelle. Unless you want chamfered edges on top, which are always custom orders.
I would gladly sell you some (I work in building materials trade), but unfortunately, I can’t get into your area *g*
The structural demands for a freestanding gabion measuring 150 cm (59 inches) high and 30 cm (12 inches) wide are considerable. A foundation with appropriate drainage must be constructed according to the specific requirements to ensure the gabions stand firmly and stably and do not sink or shift at any corner or side. For each linear meter, two supports must be concreted in place at the center (e.g., steel pipes or steel posts) that should be about 10 cm (4 inches) shorter than the height of the gabion so they remain invisible. Gabions over 100 cm (39 inches) high are not stable on their own and there is a risk of tipping over.
The steel mesh cages (usually supplied as kits) must be filled by hand; post-compaction is not possible because they are not designed for this, and the connectors between the sidewalls are also not intended for this purpose.
The infilled soil would push the gabions outward. Furthermore, as I understand it, you might not even see the gabions because your property is situated higher than that of your neighbors, correct?
Regarding gabions, I would recommend contacting the company Unger and Bultmann in Ahrensburg; they can provide very good advice and might have a suitable solution. Keep in mind, however, that gabions usually have a delivery time of about one week plus assembly time. Filling them is very labor-intensive, and the foundation curing time should not be underestimated.
L-shaped retaining walls (angle walls) are the best choice. There are many manufacturers in your area, such as Siemsen in Schwarzenbek, Rekers Concrete Works in Spelle, Westerwelle in Herford, Seling Concrete in Melle, possibly Hacon in Rellingen, and depending on their flexibility, Berding Concrete.
For the load case of car traffic (5 kN/m² or 104 psf), these walls are usually kept in stock, at least this is my experience with Siemsen and Westerwelle. Unless you want chamfered edges on top, which are always custom orders.
I would gladly sell you some (I work in building materials trade), but unfortunately, I can’t get into your area *g*
Hello bauXpert
and thank you very much for your detailed feedback. Last week, I sent quite a few emails to the companies and also spoke with Unger/Bultmann by phone.
A good solution is now emerging (thanks to you as well). I’d like to share our probably final version here for future readers with a similar problem:
- Angle supports are actually much easier to get than my excavation contractor made me believe. He mentioned a delivery time of 2-3 weeks. In the end, I could have gotten the supports within a week from about 40% of the suppliers. Shipping costs, however, should not be underestimated (we needed 6 meters in heights between 80cm and 150cm (31 inches and 59 inches) and would have paid between €375 and €620 in freight) – certainly justified due to the weight of 4 tons, but still quite a hefty amount. We finally found a local building material supplier who could pick up the supports from another dealer about 50km (31 miles) away and deliver them for €15 (we are located in southern Lower Saxony).
- Angle supports have the advantage of a standardized structural design, so no additional engineering calculations are necessary. They come in standard heights (130cm (51 inches)) and then in 25cm (10 inches) increments higher or lower. In width, they are available in 50cm (20 inches) and 100cm (39 inches).
- For the entire stepped wall, we would have paid about €3000 in total.
- Unger provided us with excellent and dedicated advice: Gabions are also possible as retaining walls in these dimensions. However, the costs become quite high. The gabions would likely be more than 1 meter (39 inches) deep. They are anchored with a geogrid that extends about 1-2 meters (39-79 inches) into the ground from the gabion. This provides the necessary stability. Since there is no standardized structural design for this, the engineering must be calculated individually, which makes this option quite expensive and time-consuming.
- After further research and based on the current situation, we will implement a different / third option: We will use natural stone bollards set in concrete. The costs for this option are about 25% lower than for the angle supports (including labor costs), the color can be selected (sandstone colors, various shades of gray and red), and we also like the appearance much better than the bare concrete supports. We also found out that there is a dark concrete variant for the angle supports, which would look almost like anthracite and thus much more modern. According to the landscape gardener, the natural stone option also allows for wall heights over 150cm (59 inches), and the steps can be finer due to the narrower width (20cm (8 inches)) of the stones.
Thanks again for the great help, which really brought us forward a lot, and I wish you a successful new year
tabaluga
and thank you very much for your detailed feedback. Last week, I sent quite a few emails to the companies and also spoke with Unger/Bultmann by phone.
A good solution is now emerging (thanks to you as well). I’d like to share our probably final version here for future readers with a similar problem:
- Angle supports are actually much easier to get than my excavation contractor made me believe. He mentioned a delivery time of 2-3 weeks. In the end, I could have gotten the supports within a week from about 40% of the suppliers. Shipping costs, however, should not be underestimated (we needed 6 meters in heights between 80cm and 150cm (31 inches and 59 inches) and would have paid between €375 and €620 in freight) – certainly justified due to the weight of 4 tons, but still quite a hefty amount. We finally found a local building material supplier who could pick up the supports from another dealer about 50km (31 miles) away and deliver them for €15 (we are located in southern Lower Saxony).
- Angle supports have the advantage of a standardized structural design, so no additional engineering calculations are necessary. They come in standard heights (130cm (51 inches)) and then in 25cm (10 inches) increments higher or lower. In width, they are available in 50cm (20 inches) and 100cm (39 inches).
- For the entire stepped wall, we would have paid about €3000 in total.
- Unger provided us with excellent and dedicated advice: Gabions are also possible as retaining walls in these dimensions. However, the costs become quite high. The gabions would likely be more than 1 meter (39 inches) deep. They are anchored with a geogrid that extends about 1-2 meters (39-79 inches) into the ground from the gabion. This provides the necessary stability. Since there is no standardized structural design for this, the engineering must be calculated individually, which makes this option quite expensive and time-consuming.
- After further research and based on the current situation, we will implement a different / third option: We will use natural stone bollards set in concrete. The costs for this option are about 25% lower than for the angle supports (including labor costs), the color can be selected (sandstone colors, various shades of gray and red), and we also like the appearance much better than the bare concrete supports. We also found out that there is a dark concrete variant for the angle supports, which would look almost like anthracite and thus much more modern. According to the landscape gardener, the natural stone option also allows for wall heights over 150cm (59 inches), and the steps can be finer due to the narrower width (20cm (8 inches)) of the stones.
Thanks again for the great help, which really brought us forward a lot, and I wish you a successful new year
tabaluga
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