Special foundation due to poor soil bearing capacity

Hello everyone,

Has anyone had to carry out a special foundation such as pile or caisson foundation or soil improvement (CSV) due to poor load-bearing capacity of the soil? Our soil consists of about 80cm of topsoil, then a 4m poor layer of non-load-bearing soil, and only after that comes a load-bearing layer.

What did you decide on and what were the approximate costs? Soil replacement is not an option for us. And how did you manage to roughly estimate the costs beforehand? Most civil engineering companies want the complete structural calculation of the house including the civil engineering statics for this. However, construction companies usually do not provide these before signing the contract, and certainly not free of charge. We have not yet bought the property, but it would be ideal for us. Now we are considering how to approach the matter without causing a huge amount of costs in advance and still be able to estimate how high the total effort will be in the end. We would appreciate an exchange.

Best regards

I think that you will find the best information in your neighborhood. In SH there are areas where you have to hit the load-bearing layer exactly, because below that it becomes difficult again - e.g. west of the Jadebusen....

In the neighborhood, there are unfortunately no houses that have had such a problem yet.

Are you building on peat/marsh?

Pile foundation is not unusual in our area. We had to drive them up to 13m deep and installed a total of 25 driven piles. 23 for the house and garage. 2 for the terrace roof and poured a strip foundation above them. We paid about 750 euros all in per concrete pile.

Do you have immediate neighbors?
Due to vibrations, piling is not allowed in certain cases because adjacent buildings could be damaged.
In this case, bored piles are usually installed. This method is almost vibration-free. However, it is unfortunately also more expensive than piling.