Interpretation of soil investigation for construction

Hello everyone,

we have a report on the geotechnical investigation for a possible plot of land. Since I am not a geologist, I find it somewhat difficult to assess the whole thing. Are there experienced people here who can draw conclusions for construction from such a report? Who does a layperson usually discuss such a report with before buying a plot of land?

Especially regarding the topic of foundation and infiltration, there are statements in the report that read very negatively to me as a layperson.

a) Infiltration: Due to poor soil permeability, it is recommended to provide overflow devices for heavy rain events.

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b) Foundation: Clay horizons with weak geotechnical properties:

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Thanks and regards

Infiltration is common for clay soils. I would avoid a soakaway if possible; if one is senselessly required, it should have an overflow to the sewer. Under the driveway, it is better to gravel generously, especially if permeable paving is used.

Regarding the foundation, I don't see anything particularly negative at first. Soil replacement is probably not necessary (only if weak layers are encountered). According to the report, you will need a thicker floor slab, which is not a big deal. Actually, only 30-40 cm of gravel under the floor slab is recommended.

To me as a layman, this looks okay at first, similar to our subsoil. In such an area, I would only construct a basement with a [weiße Wanne], and I would not skimp on gravel. For outdoor areas, pay attention to the slope; water can run downwards under the driveway in the gravel.

I don't know much about it either, but it sounds very expensive. That is probably something to discuss with a [Erdbauer], [Statiker] or [Architekt].

Does not have to be expensive, nothing is mentioned here about pile foundations or the like. However, it is important to be aware that with the same ground conditions very different foundations are possible and that soil can change within just a few meters. Therefore, also the question of where the soil survey comes from and exactly where on the property it was conducted.

No, there is nothing about pile foundations. However, it also says that a foundation with strip footings is not recommended because they settle too much. So that only leaves:

It looks like they would suggest a gravel cushion, lined with a textile to keep the gravel from washing away. That is something I would not want.

The foundation with _independent_ strip footings is not recommended because they can settle at different rates. So what is usually done with prefabricated garages: pour in 3 strips and put the concrete garage on top. But this is completely uncommon for single-family houses. A beam grid, on the other hand, is also just strip footings, but all well connected so that they settle evenly. Geotextile under gravel is also absolutely common with clay soil; everyone in this settlement has it.