ᐅ Building a House on an Existing Basement: Issues with the Foundation

Hello everyone,

I am planning to build a new solid house on top of an existing basement (previously there was a prefabricated house on it). The basement and the old house were built in 1990. Since there is very little groundwater, the basement is quite dry. No defects are visible.

Details about the basement: strip footing with a width of 50cm (20 inches), exterior basement walls 20cm (8 inches), interior walls 15cm (6 inches).

Now, we had a structural engineer inspect the foundations and the basement. A soil report was also prepared. It turns out that the foundations were already fully utilized with the current prefabricated house. The new solid house will be taller and significantly heavier, as a concrete floor slab will be installed between the ground floor and the upper floor.

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

My question is about feasibility and cost-effectiveness. Has anyone had experience with whether it makes sense to reinforce the foundations, or if it is more practical to demolish the basement and rebuild it completely?

I would prefer to keep the basement since its basic dimensions are suitable. However, if reinforcing the foundations turns out to be too expensive, demolition would also be considered.

Does anyone have experience with this and could possibly explain how a foundation reinforcement usually works?

Thank you very much.

Best regards,
Michael

Phew, the house is younger than you [emoji2]

Is it generally economical to consider demolition?

Yes, there are several reasons, and it would be too much to explain. Half of the house is already no longer standing anyway ;-)

I have just received information that my foundation needs to be widened by 25 - 30 cm (10 - 12 inches). Perhaps this information might still be helpful.

Does anyone have any useful advice on how this can be done?

Thank you.

Only someone who could tell you that the foundation needs to be widened can give you that answer ;-)

You need a professional with detailed local knowledge who can provide you with a specific quote. Everything else is pure speculation.

In general, I wouldn’t expect you to save much.

Has anyone else had experience with how a foundation widening is carried out? Is it done entirely from the outside, or does the basement also need to be opened up?

Thank you