Assessment of soil report: Basement or not?

The OP actually wants to build without a basement.

Sorry, I had already forgotten by the time I reached the end of the OP’s text. You are of course right with your remark. The soil report says, besides a lot of technical gibberish about the foundation recommendation of a 2m gravel support layer (bedding) which must comply with a certain standard. That says everything for me. Fortunately, there is already a big hole which needs to be slightly enlarged and afterwards it can be filled layer by layer. Up to a certain height. This must be determined in the planning process. Do you want a ground-level entrance to the house or go up 1, 2, 3, etc. steps. The question whether a general contractor or architect is better must be answered individually. What I would not do without in either case is the building surveyor who supervises the project from the beginning.

The soil report basically only indicates the removal of fill and replacement with gravel. The soil underneath is not good (clay is always problematic) but it is sufficient for a single-family house. Due to the planned height and the morphology of the plot, more fill is of course necessary (so that the house is not floating in the air).

A basement becomes cheaper if the soil excavation has to be done anyway. For example, up to 4 m below ground level there are layers of peat/meadow lime/fill etc. that definitely need to be replaced. For a slab foundation, 4 m of gravel must then be filled again. If you build a basement instead, you save the filling.

In this construction project, it does not look like a basement would "pay off."

Regards

I paid 50 EUR per m³ for delivering, installing, and compacting gravel. Taking a pit of 120m² and 4m depth... sums up to 24,000 EUR, financed at 3.5%. A basement, white tank, costs? 80,000? Financed at 3.5%... It hardly “pays off” if you don’t have the money and don’t need the 80m² large basement. It also needs to be heated, furnished, etc.

Building a house "never really pays off" anyway. Of course, in the described case, you already have the finished pit for a basement, which you would otherwise fill back in for €24,000.

Of course, in such a case, you can also use special foundations (piles or vibrated displacement columns) to avoid having all the excavated material that you have to dispose of expensively. But it was only a theoretical example.

In this case of Araknis, none of that applies and the cheapest option is a normal slab on the gravel cushion.