Soil survey before purchase or before construction

I have now found plots of land for sale nearby.

An acquaintance said that I should have a soil survey done before the purchase, even if it costs money, to avoid unpleasant surprises later.

1. How was it for you, did you do it or not (and maybe regretted the decision)?

2. Costs: 400 to 1000 euros, says Google, is that about right?

3. Who does a soil survey and what should one pay attention to?

We had it done for about €900 including soil analysis by the laboratory before the purchase. This was also recommended in the information letter from the city. The drilling should be sufficiently deep, it certainly also depends on whether there is a basement or not. Unfortunately, we did not pay that much attention to this back then. Only 2 drillings were carried out. One at 3.20 m, the second was aborted at 0.70 m due to an obstacle. The latter, however, was a mistake. Our current architect would like to have a new report made with drillings at the corresponding depth (2-3). It is another €1000, but we don’t want to experience surprises during construction or even later. We are building without a basement. The first report was made by a geologist.

Soil reports should be prepared, if possible, before purchasing the property. They contain essential information regarding the scope and thus the costs of the excavation, foundation, site drainage, and waterproofing of the building. The costs for a soil report for a single-family house with 3 dynamic probing tests are approximately between € 1,000 and € 1,500 gross. They are carried out by engineering firms for geoconsulting/geotechnics, geologists, etc. For the scope of the soil report: see attachment. If necessary, the report should be formulated and tendered by a geologist/engineer/architect as a specification sheet in order to obtain comparable offers from several engineering firms on a uniform basis.

I have read the following on the topic of soil surveys: "The surveyor must have at least the rough plans from the surveyor so that he can see where the house will be built later. He then carries out so-called small drillings at 2 diagonally opposite corners (or at all corners, but that increases the price) to a depth of 6 meters."

But if I want to have this done before purchasing the property, I do not yet know where and how the corners of the later construction will be located. Or is it simply irrelevant exactly where the drillings are done?

You need a site plan from the surveyor quite early for the planning! We sent this site plan along with the first draft to the geologist. We also had the site plan and soil report done before purchasing the property.

That is not possible if you have to decide on a plot within two weeks like we do; we can only conduct a soil survey after the purchase.