ᐅ Building a Retaining Wall in the Garden: Formwork Blocks or L-Shaped Blocks?

xMisterDx schrieb:

Your support will transfer the force to its support structure—where else could it go? And the neighbor’s support won’t be designed for that.

That could very well be the case.

BiffBiff schrieb:

How far do I need to stay away from the boundary to prevent any sliding? We want to hire a structural engineer to answer this question. To what extent is a structural engineer responsible if sliding occurs? And how about the neighbor?

LOL – what good is keeping a distance from the boundary?
Normally, for a slope cut on soft ground, a 45-degree angle should not be exceeded (without a structural calculation). So, with a 2m (6.6 ft) excavation by the neighbor, you’d need at least a 4m (13 ft) setback for the slope up to your retaining wall. Then keep in mind that the retaining wall itself will exert significant pressure from the soil behind it.
I would recommend doubling that distance for the setback and then slope it. That means your retaining wall, plus about 8m (26 ft) of slope up to the neighbor’s original ground level.
The foundation should also be sufficiently deep and made of concrete. How is the drainage planned?

Please upload some photos again. What does the site currently look like? What exactly is the neighbor planning? Have you (are you even communicating?) discussed this together? How much space do you have?

jens.knoedel schrieb:

Then it probably comes down to "We can do this together!". Everything else will be a disaster.

P.S. You can't prevent the visual disaster at the neighbor's either...

Visual disaster is the right description. Just imagining having to look at a 3m (10 feet) high retaining wall 😱
Has the neighbor already carried out the excavation as planned? How has it been secured so far?
Regarding excavating on the property, §909 of the building code specifies exactly who is responsible for what. We have looked into this as well, since our property is also on a slope and on one side we had to excavate too (although only 1m (3 feet)).

In the end, there’s no other option but to build a 3m (10 feet) high wall. The original poster probably doesn’t care what the neighbor can see. A better solution would be if both of you create a terraced garden, so that maybe around 1.5m (5 feet) remains at the boundary that needs to be supported with L-shaped retaining walls.

I also think a terraced garden is a great way to add structure. At the top, you can plant trees, one level below you can have flower beds, and then there’s a flat area with grass for the children to play on.

I also see this quite often here, where neighbors build 1.5–2m (5–6.5 feet) high concrete walls between their properties to keep the entire plot at exactly the same level.

BiffBiff schrieb:

3) How much does this roughly cost per running meter? Does anyone have fairly recent experience?

Since we are also planning a shuttering block wall, maybe the following guideline prices will help you (offer status 12.2023, all net prices):

Excavation for foundation trench 1 x 0.6 x 0.8 m (3.3 x 2 x 2.6 ft): 43.00 € per running meter
Concrete foundation C25/30 1 x 0.6 x 0.8 m (3.3 x 2 x 2.6 ft): 130.00 € per running meter
Shuttering block wall 50 x 36.5 x 25 cm (20 x 14.4 x 10 inches), including reinforcement and concrete: 197.00 € per square meter
Cap slabs: 36.00 € per running meter
Drainage:

... since the forum currently does not allow editing...

Drainage: €37.00 per linear meter
Dimple membrane: €10.70 per square meter

We will have approximately 20 linear meters, with an average height of about 1.5 m (5 feet), so similar to your situation.

However, the situation regarding the neighboring property will probably make everything more complicated and likely more expensive.