Is the soil report for construction also usable for basement construction?

Hello everyone,

we had a soil investigation report conducted for our new build of a single-family house. The plan was to forgo a basement and build on a slab. This has now changed and we are planning with a basement. Unfortunately, the boreholes were only drilled 3m deep due to the planned slab.

Now my two questions:

1. Can I still use this report for planning a basement or do I have to bite the sour (more expensive) apple and have another one done?

2. Is the soil suitable for a basement or is it better to avoid it due to high additional costs? I really can't interpret all the key values.

No one has an idea or advice?

You will have to dig deeper than 3 meters for the basement. Either a new survey, which also won't give you 100% certainty, or simply take the risk. In my experience, I would do it without an additional survey.

You will have to dig deeper than 3 meters for the basement. Either a new expert report, which also doesn't give you 100% certainty, or just take the risk. In my experience, I would do it without another expert report.

Thanks for the post. Do you mean I have to dig deeper than 3 m during the excavation or when drilling for the soil survey? Why would you do it without another expert report in my place? As I said, I have no knowledge of all the geological parameters at all.

Think that you have to dig at least 4 meters. One story height + ceiling + floor + floor slab + substructure. If you want to drill again, then 5-6 meters for safety. Why I would take the risk: how likely is it that it changes compared to the 3 meters? How many drillings do you have? We drilled at 3 locations, made 5 test pits, and still had a hole from the old house. In the end, a lens of clay ran across the construction window. We had not found that with any inspection. That’s what I meant that another drilling does not give you 100% certainty. Your soil is Z0 max. Z1.1. So easy to get rid of. Maybe you can also use it on the property for modeling. Soil class 4-5 is also easy to remove with smaller machines. If you are willing to bear the costs for a basement, your soil is no problem.