ᐅ Building a Prefabricated House on an Existing Basement – Any Experiences?

Hello everyone,
I’d like to get your opinion on a topic—maybe someone has dealt with this before.

We have purchased a plot with an existing old building. The house is old and we don’t like it, so we want to demolish it.
However, the basement is still in great condition, so we’re considering keeping the basement and building the new house on top of it.
Does anyone have experience with this? What should we keep in mind? Do you think it’s worth it?
This would also save us the site development costs as well as the demolition of the basement.
We haven’t consulted an architect yet; that will be the next step.

Thanks a lot for your feedback!
Best regards

I am generally in favor of reusing the basement: foundation, house connections and penetrations, storage room – everything is already there. Removing all of this just to rebuild it again doesn’t make much sense on its own; after all, "architecture" is not the main focus of a basement. Does the height relative to the terrain also fit your plans for how the new building should be positioned?

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Yes, that's a good point.
The basement raises the whole structure quite a bit, and we actually wanted a ground-level entrance. That will now be dropped, but in return, we save money and gain living and usable space. Otherwise, we would have built without a basement.

This will be a calculations exercise to determine which option is ultimately more cost-effective. I’ll just write down my thoughts without knowing the situation on site:

- Demolishing the house without damaging the basement is more complicated and expensive than removing everything completely with an excavator.

- Are renovations needed for the basement? Waterproofing, insulation, etc.?

- Exterior dimensions: Forcing a prefabricated house to fit the existing basement dimensions can become very costly. With fixed modular sizes, it may even be impossible; the house would have to be smaller, and the exposed basement would need to be sealed from above.

- Does the basement ceiling support load-bearing walls, or does wall-on-wall construction have to be used, which would mean the basement footprint already dictates the future house layout?

- Are existing cable and pipe penetrations usable, or are new openings required?

- Does the staircase exit in a suitable location?

There are certainly more points that would have to be worked out in the calculations.

Theoretically possible, but in most cases not a good idea in practice.
In addition to the points made by @Mottenhausen, the structural stability of the foundation and the connection/transition between the existing structure and the new building must also be considered.
Overall, the savings are likely to be small or non-existent.
I would recommend demolishing the basement as well.

I do not share the pessimism of the previous speakers (and hopefully will find time this evening to explain why).

The question here was specifically about a prefabricated house, where the structural conditions differ and where the basement often does not follow the floor plan of the living area.

Perhaps the original poster will still upload some pictures, first of the existing building from the outside and of the site, which would help clarify some of the speculation.

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