House construction on an existing basement, problems with the foundation

Hello everyone,

I plan to build a new solid house on an existing basement (previously a prefabricated house stood on it). The basement and the old house were built in 1990. Since we have hardly any groundwater, the basement is quite dry. No defects are visible either.

Data on the basement: strip foundation with 50cm width, basement exterior walls 20 cm, interior walls 15 cm.

Now it is so that we have had the foundations and the basement checked by the structural engineer. A soil report was also created. It turns out that the foundations are already fully utilized with the current prefabricated house. The new solid house is also supposed to be higher and significantly heavier because a concrete ceiling is to be installed from the ground floor to the upper floor.

I have now heard and learned that foundations can be subsequently widened and reinforced.

My question is economical. Are there experiences whether it is worthwhile to reinforce the foundations or whether it makes more sense to demolish the basement and build a completely new one?

I would like to keep the basement itself since the basic dimensions actually fit. However, if the foundation reinforcement turns out to be so expensive, demolition also comes into consideration.

Does anyone here have experience with this and can maybe also explain to me how such a foundation reinforcement takes place?

Thank you very much

Regards Michael

Phew, the house is younger than you [emoji2]

Is it generally economical to talk about a demolition?

Yes, there are various reasons and it would be too much to write. The house is already half gone anyway ;-)

I have now also received the information that my foundation needs to be widened by 25 - 30 cm. Maybe this information will still help. Does anyone have a helpful tip for me on how to proceed? Thank you

That can probably be told to you by the person who could tell you that the foundation needs to be widened ;-)

You need a specialist with precise local knowledge who can give you a concrete offer. Everything else is pure speculation.

Generally, I would not expect that you can save significantly.

Does anyone else have experience with how such a [Fundament Verbreiterung] is done? Is it done entirely from the outside or does the basement also need to be opened?

Thanks