ᐅ New Basement Beneath the Foundation of an Existing House

Hello everyone,
I’m new here and have a feasibility question. It concerns a house that already has a basement and a foundation about 1 meter (3 feet) thick. The house was built in 1964. My question is whether it would be possible to expand the basement below this building, more specifically beneath the foundation (which I think is a better option than breaking up the foundation), potentially adding two underground levels. At the rear, there is plenty of green space adjacent to the property, and behind that are houses we also own and rent out. If this is possible, how would you estimate the costs?

Chris-Cross schrieb:

If this is possible, how would you estimate the costs?

Anything is possible. Financially sensible? Definitely not...

I had already considered that, but purely out of curiosity, how much additional cost would there be compared to if I were to basement the greenfield area directly under the house at the ground level, up to the edge of the house (per m²)?

So you don’t want to add a basement to the existing house but rather build a basement as an extension?
Why not an above-ground extension?

How can you provide an estimate without any information?
Groundwater? Soil type? Area? Use of the basement?

But just if you dig deeper than the existing foundation, you have to underpin the old structure. That alone will already cost a lot (the deeper you build, the more expensive the underpinning). But no one here can give an estimate for that either.

So I believe if you get a number here, it will be wrong.

Best regards

Chris-Cross schrieb:

I’m here and have a feasibility question right away. It’s about a house that already has a basement and a foundation about 1 m (3.3 ft) thick. The house was built in 1964. My question is, would it be possible to expand the basement under this building, more precisely under the foundation (which I think is a better option than tearing up the foundation), possibly with two underground floors. Adjacent at the back there is a large green area and behind that, houses we also own and rent out.

A foundation one meter (3.3 ft) thick does not indicate a problem-free ground to begin with. And now the plan is—using horizontal drilling, FlowTex style?—to insert a two-story (second and third) basement under the building, even extending beyond its footprint. No further honors, your questions (or whatever that is)—to me, this sounds like a top-tier fake alarm. We’ve been missing a “smile” section here, thanks for providing it!

---

https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/