ᐅ Excavation pit dug too deep due to change in finished floor level

Hello everyone,

First of all, here are the key points of my house construction project:

We want to build a single-family house (prefabricated house, timber frame construction).
This includes a prefabricated basement, which according to the soil report must have waterproofing against rising seepage water according to DIN 18 195 section 9.
The foundation slab and basement are scheduled to be installed at the end of July.

A soil report has already been prepared; after 20cm (8 inches) of topsoil there is clay, heavily silty.

Now to my somewhat difficult to explain problem:
I have already had the excavation done because I could dispose of the excavated soil cheaply (otherwise the cubic meter would cost about €8), and the civil engineering companies in the area are very busy.
To avoid water problems in the excavation pit, we did not dig down to the required depth but left about 25cm (10 inches) of soil in place, planning to remove this 2-3 weeks before the basement installation. After that, a 15cm (6 inches) capillary-breaking layer would be installed and that would be sufficient. I have already uncovered the wastewater sewer and connected it to the excavation pit so it cannot fill with water.
Since I now have some time, I marked the finished floor height and realized that this would be about 50cm (20 inches) below the top edge of the topsoil. The finished floor height in the development plan is correct. Based on this, I contacted the municipality with this issue, and now the finished floor height has been raised by 60cm (24 inches).
Now I have the problem that I am too deep, and the earthworks were not done with a smooth-edged excavator bucket but with a toothed bucket (soil class 5-6).
To gain the 60cm (24 inches) in height, I now need to compact the subsoil again and fill it up by 20cm (8 inches) plus the 15cm (6 inches) capillary-breaking layer.

Can someone help me with how and with what material I can refill these 20cm (8 inches)?
Or how I should proceed further.

Thank you in advance for your help.

Best regards

Tobias

Hello Tobias,

tobi-hausbau schrieb:
Can anyone help me with how and with what material I can refill these 20cm (8 inches)? Or how I should proceed further.

This should actually be described in the soil report; what is noted there?

Kind regards