ᐅ Leveling a sloped plot using reinforced Berlin retaining walls with steel bracing

I am considering purchasing a plot of approximately 468 sqm (5,040 sq ft) to build a single-family house. The rear part of the plot is intended to be used as a garden. However, the back section, about 10 m (33 ft) deep and approximately 16 m (52 ft) wide, slopes steeply (maximum height difference around 2.5 m [8 ft]). At the end of the property, there is a stream that is part of a nature reserve. The neighboring properties on the sides have not leveled their slopes but have either planted grass or created terraces/steps.

For me, a purchase is only an option if I can level the rear part. An acquaintance from the construction industry gave me the following recommendation: Berlin shoring system with steel infill, and greening the wall on the sides facing the neighbors.

1) Is this technically feasible?
2) Are approximate costs of €25,000 realistic?
3) Is obtaining planning permission likely?
4) Which authority should I contact to clarify the permit before purchasing?

Thank you in advance for any advice!

Bau_dus schrieb:
1) Is this technically feasible?

Sure, that’s exactly what a retaining wall built using the Berlin trench method is for.

Bau_dus schrieb:
2) Are approximate costs of 25,000 € realistic?

No, definitely not. In the worst case, costs could run into six figures, because constructing a retaining wall in a stream bed could be complicated.

Bau_dus schrieb:
3) Is a permit conceivable? 4) Which authority should I consult about the permit before purchase?

Probably multiple authorities will have a say here: the local water management agency, environmental office, city authorities, and so on.

The biggest issue will be that you’re interfering with flood protection by narrowing the potential flood channel instead of letting your rear garden flood. You might also be damaging a designated floodplain area (a red flag in any permitting process), and so forth.

Your long-established neighbors will likely become quite envious since you would end up with a great property, which is usually the beginning of the end.

Only the Berlin shoring or an additional concrete wall.
The Berlin shoring will eventually rot.
I think 25,000 euros is too low for the reasons listed by Mottenhausen.
You will also need a fence on top, so nobody falls over the wall at the back.

Check with the building authority / planning department. They can tell you if it would be approved.

Don’t forget, the whole area still needs to be backfilled. That involves a significant amount of soil, excavator hours, truck transport, and compaction time.

Thank you very much for the very helpful assessments. I will contact the authority by phone.