ᐅ Constructing a Cost-Effective Retaining Wall / Slope Stabilization

Hello everyone,

The weather is steadily improving, so it’s time to start planning the outdoor area. Parts of the property will need to be filled in. The site has already been surveyed, and leveling at the lowest point would require approximately 2 meters (6.5 feet) of fill soil.

There are gardens adjacent to the property on all sides, so I will need to build a retaining wall accordingly.

I have already spoken with the local building materials supplier. He suggested simply making a foundation by excavating 1 meter (3.3 feet) deep, then adding a 20 cm (8 inches) layer of crushed stone, followed by 80 cm (31.5 inches) of reinforced concrete. On top, concrete blocks would be placed, reinforced with rebar and filled with concrete. He recommended using blocks sized 26 cm or 29 cm (10 or 11.5 inches), but said he could not provide structural calculations or any official advice. He quoted me a material cost of about 3,500 euros.

Nothing was mentioned about installing drainage. I’m also unsure where the water would be directed since all sides border neighboring properties. Or did I misunderstand the purpose of drainage—is it to carry water away from the retaining wall to somewhere else?

Now my question is whether there might be other, possibly more cost-effective ways to do this? Precast L-shaped concrete elements are available here, but they cost about three times as much and require a mini-excavator for installation.

Another option I considered is to reduce the wall height to 1 meter (3.3 feet) and create a steep slope up to the fill level. However, I’m not sure how steep the slope can be without causing sliding. The property will later be enclosed with a dense hedge for privacy. As far as I understand, the wall must be set back 2 meters (6.5 feet) from the property boundary to avoid problems with height restrictions, especially because the ground has already been raised by 2 meters (6.5 feet).

I want to minimize the amount of space lost to make the most of the property, but I also want to keep costs relatively low since there are many other projects planned.

Since I can’t see the wall from my side and the neighbor is a daycare center, appearance is not a major concern for me.

Maybe you have some ideas or tips on the best way to approach this.

Thank you in advance for your help.

Webmaster-uk schrieb:
...not to build the wall up to 2 meters (6.6 feet) but only 1 meter (3.3 feet) and then create a steep slope up to the final fill height. The question here is how steep the slope can be without slipping.

Less than 60 degrees and planted will hold.

Hello, sounds like what we had. Our deepest point was 2 meters (6.5 feet). We then used hollow concrete blocks, added steel reinforcement, poured concrete, and extended it about 35 meters (115 feet) to the left and right in total.

On both sides, the depth became shallower.

Basically, we don’t go 1 meter (3.3 feet) into the ground unless the soil pressure is very high.

I would have chosen a maximum of 40 degrees. The slope needs to be maintained occasionally, even with ground cover plants. At 40 to 47 degrees, this is already hard work.
I would also install an erosion control mat.

Privacy screen: you are adding 2 meters (6.5 feet) of fill. First, test how much can actually be seen from below.

Thank you very much for your answers.

I looked it up online because I apparently can’t figure out how to convert the slope into exact numbers, but I’m still confused about this :-/

How much land do I lose at a 60-degree slope, meaning how many meters (feet) of distance do I need from the wall to the highest point?

@HilfeHilfe
Did you build the wall yourselves and pour the concrete mixed in a mixer, or did you have a concrete truck with a hose deliver it?
I’d like to mix the concrete myself to save costs but I’m not sure if I’m underestimating the work.
It would be about 45 meters (150 feet) of wall to build.

What thickness of stone did you use, and did you have a structural engineer or someone calculate the load to make sure you chose the right size stones?

Do I generally need to install drainage here, or can I skip that?

At 60° it would be 60cm (24 inches).
At 40° it would be 120cm (47 inches).

Our new wall, which is also an exterior wall of the house, has drainage, unlike the old walls.
I have deliberately not seen any drainage with all the L-shaped blocks being installed everywhere at the moment.

Do you have a concrete mixer? Using just a shovel, it will probably never feel like you’re finished.