Loess Loam & Shell Limestone as Building Ground: Unexpected Expenses / Costs

We were quoted construction costs of 1000€/m2 for a basement about 2-3 years ago (that was without underfloor heating). Of course, it depends on the fittings, whether it is a utility or a living basement. Excavation and disposal costs are added on top of that.

The costs for the basement are difficult to estimate so far due to the unknown dimensions of your construction project (size, equipment?). The same applies to the associated incidental construction costs. If things go badly, they might even double the basement price.

How are we supposed to know what the basement will cost? We don’t know the conditions of your plot, nor the size of the basement, nor its equipment.

Of course, it depends on the equipment, whether it’s a utility basement or a living basement. Excavation and disposal will be added on top of that.

The house will have an exterior area of approximately 12m x 7.5m. We envision the basement as fully underground, but only as a utility basement.

If the municipality already announces difficult soil conditions, I would be cautious about buying the property without my own soil survey given a limited construction budget.

And exactly on this point we are uncertain whether the points mentioned in the documents are merely standard provisions or not?!

And exactly at this point we are unsure whether the points mentioned in the documents are merely standard specifications or not?!

Even here, without a soil survey, one can only speculate. The municipality surely knows the local (construction) ground and therefore - certainly also for its own safety - provides these notes. They will be specific to your region but general in the sense that no one can specify the extent of the listed properties specifically for your plot without having obtained a geotechnical survey. In times when plots are selling like hotcakes, your municipality will save the money for a survey and stick to such general but region-specific notes. Regarding cellar costs, I can give you our current prices (the cellar has just been completed).

Residential cellar, floor slab area 10x12m + 1x4m bay window, clear room height 2.66m, KFW 55, waterproof concrete exterior walls + KS interior walls, black coated + 16 cm XPS insulation on the earth-contacting parts.

Additional costs approx. 30k, shell construction costs approx. 70k, insulation and sealing approx. 22k, interior finishing I can only estimate roughly and will probably add another 60k.

Hello Doomonti,

there is almost everywhere geogenic arsenic in the area. Our soil was quite similar. The proof that the arsenic is geogenic would be more expensive than just disposing of it right away. You should expect that. You have it everywhere in that area anyway. Have Z.1.1 arsenic and Z1.2 surcharge offered. Then take Z1.2 as the worst case. Especially with the excavation, the differences in the offers are huge. Therefore, definitely inquire with several companies. The soil is stable. Gravel layer and then normal foundation construction. 60k including cellar and excavation will not be enough. It is an expensive area to build in. I estimate you're about 20k-30k down for excavation and disposal with setup, etc. What the municipality writes is more or less an excerpt from the soil assessment. They just protect themselves with that. Soil is always the builder's risk. If the location and price are right, that would not deter me in the slightest. The description is like that almost everywhere in new development areas in the region.... A soil report will come out exactly as the municipality writes. That doesn't make the soil better or worse. If you want to avoid the risk, skip the cellar and build wider/higher.