Is a strip foundation necessary at all for a small wall?

Hello everyone,

we want to build a wall from these "Lego concrete blocks." 40cm thick, 2 blocks each 80cm high, and about 25m long in total. I think you know which blocks I mean. Linking is not allowed in the forum and I am sticking to that.

The ground is currently a gravel layer that was compacted 3 years ago when construction took place there, and opinions differ somewhat regarding the ground:

- Recompact the soil, level/plan with gravel, place concrete blocks directly on it.
- Excavate (how deep?) and put in a lean concrete foundation, place concrete blocks on top.
- Recompact the soil, make a lean concrete foundation (is 13cm enough here?), place concrete blocks on top.

What would you do or recommend? Is reinforcement needed? I would make the foundation slightly wider than 40cm, or does it not matter if it is exactly as wide as the wall thickness?

Best regards, kanuddel

What might still be relevant: The wall is intended to serve as a slope retention. We have a terrain difference of 3-4 meters and want to save at least 1.6 meters here.

The background is, we have built a hall there and around the hall, so also where our future garden is supposed to be, there is first 3 meters of flat area and then a 45-degree slope up to the natural terrain profile. We lose a lot of garden space there. Therefore, we wanted to build this wall 1 meter away from the hall (so that some repairs could possibly still be done if necessary). And the excavated material from the house construction can also be stored there. After that, it continues steeply up to the natural terrain profile and is then secured at the top so that no one falls down.

Hello kanuddel

You probably mean the concrete formwork blocks.
I am not familiar with 40s. 30s. And 80 high per block? I know 20s and 25s.
But imagine, they have to withstand the earth pressure of 160 cm of soil. They can only do that if a "foot" helps. So: dig 80 cm deep, fill in 15 cm of well-compacted RCL. Then make a foundation (1:4, not lean concrete) about 100 cm wide with rebar. On that, you can build the concrete formwork blocks to absorb the pressure. Of course, vertical rebar (at least 12 mm) from the foundation up to as close as possible to the top of the wall. Horizontally, two rows of rebar. Fill to the top with concrete 1:4. Otherwise, it won’t work.
Or take L-blocks right away, which are designed for that.
Otherwise, the wall will lean toward the abyss.

Steven

: I think he means concrete block stones and not formwork stones.

Exactly, concrete block stones, not shuttering blocks.
80x80x40cm and 900kg heavy per piece

1m³ of soil weighs between 800-1400Kg, so there is still a lot of earth pressure against the wall. Without anchoring the stones (steel + concrete foundation) or actually assembling them in a Lego-style (interlocking) way so that the wall becomes 80 deep, the wall will "fall over" (it doesn’t simply fall over, but shifts, tilts, or something similar depending on local conditions.

At 1.6m height, certainly some things need to be considered:
• Is this allowed?
• If yes, is structural proof required? (I believe so at 1.6m)
• A picture of the situation might help to find alternatives to the probably very expensive stones