ᐅ Special foundation due to poor soil bearing capacity

Hello everyone,

Has anyone ever had to use a special foundation method like pile foundations, pier foundations, or ground improvement (CSV) due to poor soil bearing capacity? Our soil consists of about 80 cm (31 inches) of topsoil, followed by a 4 m (13 feet) layer of weak, non-bearing soil, before reaching a load-bearing layer.

What solution did you choose, and what were the approximate costs? Soil replacement is not an option for us. How were you able to estimate the costs beforehand? Most groundwork contractors require the full structural engineering calculations of the house, including geotechnical engineering, but these are usually not provided by the builders before signing the contract, and certainly not for free. We have not yet purchased the plot, but it would be ideal for us. Now we are considering how to approach this without incurring a large amount of upfront costs while still being able to roughly estimate the total effort involved. We would appreciate any shared experiences.

Best regards

I believe you will find the best information in your local area. In SH, there are regions where you need to precisely reach the load-bearing soil layer, as it becomes difficult again below that— for example, west of the Jade Bight....

Unfortunately, there are no houses in the neighborhood so far that have experienced this issue.

Are you building on peat/marshland?

Pile foundations are not uncommon in our area. We had to drive them up to 13 meters (43 feet) deep and installed a total of 25 driven piles.
23 for the house and garage, and 2 for the terrace roof, over which a strip footing was poured.
We paid about 750 euros all-in per concrete pile.

Do you have immediate neighbors?
Due to vibrations, piling cannot be done in certain cases because adjacent buildings may be damaged.
In such cases, bored piles are usually installed. This method is almost vibration-free but unfortunately more expensive than piling.