New construction - now or wait? Experiences?

It means that you need to excavate and replace about 2m (usually recycled gravel and sand) to create a load-bearing layer. It sounded very similar for our soil. For us, this was additional costs of 25k. That was in 2016.

It says "should" or "ought to" because it is only a partial picture of the ground and ultimately just a recommendation. Two meters further it can look better or even worse. Exactly how, only the excavator driver will see when he digs the pit. Ultimately, the expert cannot force you to follow his recommendations. We also have poor soil here and had to replace a lot or additionally add a lot of gravel. Some thought that was too expensive and actually found a structural engineer or house builder who simply dumped and compacted 50cm of sand without major replacement. By the way, I haven’t seen any recycled gravel here at the foundation anywhere. I have heard that you are not allowed or should not use it because it does not have defined properties or does not compact very well. When I look at the "fresh" 0/45 gravel from the foundation, it is quite sharp-edged. The recycled gravel that the contractor dumped in the driveway for me... that is much more rounded, as it had already been under railway tracks or somewhere else for many years. Whether that’s true, no idea. But it is not much cheaper compared to fresh gravel either. Okay for a driveway or garden shed. For a house, better not.

By the way, I haven't seen any recycled gravel here during the foundation work. I have it in my mind that one shouldn’t or isn’t allowed to use it because it doesn't have defined properties or it doesn’t compact very well. When I look at the "fresh" 0/45 gravel from the foundation, it is quite sharp-edged. The recycled gravel that the civil engineer dumped into the driveway for me... that is much more rounded, as it had been lying under railway tracks or somewhere else for many years. Whether that’s true, no idea. But it’s not that much cheaper compared to the fresh gravel anyway. Okay for a driveway or a garden shed. Better not for a house.

We had to get approval for the use of recycled gravel with certificates and all that goes with it. So the whole thing has to be proper and thorough from an environmental perspective. Since we have a well-known plant nearby, getting the approval was quite easy.

and Thank you for your assessment! If that cost 25k back then, we are probably at at least 30k by now.

So I paid €11 net for a ton of crushed concrete (recycled gravel) at the beginning of 2024. I think that was a very good price. That is just the material without costs for placing, compacting, etc. Geographically, I am about 50 km south of you, so it is probably similar for you. For one m² you need about 1.3-1.5 tons of material. You can calculate if you know the dimensions of the pit.

sorry typo: m³ not m²
Addendum:
Then you of course also have costs for excavation. You might be able to at least partially spread the excavated material on the property. The property is large. Disposal of the excavated material is quite expensive; I was quoted €28.50 per m³ net in 2024. The excavated volume is also significantly more than the pure pit volume since it is no longer compacted. We then spread our excavated material on a private field.