Basement construction at high groundwater level (2m)

Nordlys had it like that too:

Nordlys had it like that too:

And even as a hip roof. However, even a man sees the difference to the almost decorative attic of :-)

Ah, yes, here is Steffi's floor:
https://www.hausbau-forum.de/threads/aufbewahrungsboxen-fuer-kaltdach.37546/post-460073

thanks for the tag.

Unfortunately, the topic of groundwater lowering was unavoidable for us as only 300sqm of land is available and the groundwater level is at -2.4m.

But back to you. Please provide me with the following values:
- kf value from the soil report
- borehole depths
- depth of waterproof layer (if available)
- distance of the excavation pit to neighboring plots
- distance of the excavation pit to neighboring buildings

How big is the plot? Could you live with raising the house including the basement by 2-3 steps?

Some important keywords have already been mentioned.
It is also interesting to know that no natural hazard insurance covers damage caused by permanently standing groundwater because it is simply not insurable. A properly constructed basement according to the state of the art stays watertight for many decades even when standing in water and can, if executed in pure cast-in-place concrete construction, be subsequently renovated with injection methods as desired. Experts (and tests) say this is not possible with element construction (prefabricated parts). When building in groundwater, I would definitely include an expert in the planning phase, as serious mistakes can only be corrected in the worst case by demolition.
The costs for (y)our basement can hardly be specified exactly in a lump sum.
Many say that a square meter of basement is cheaper to build than a square meter of ground floor, for example. This has, among other things, the following reasons:
- lower story height = less material
- no lintels, shutters/blinds
- usually no walk-in shower/toilet/fittings
- usually significantly cheaper floor coverings
- usually less electrical installation
- partial or no underfloor heating at all
- less plastering effort since concrete walls usually remain unplastered
- etc.

Groundwater lowering would have cost us upwards of €40,000 which is why I carried it out myself. However, if you allocate these 40k to the basement, you come to a similar price per sqm as for the living area and the whole thing looks different again.

Really many great answers and ideas here already, thank you very much for that!

wow thank you very much for the detailed answer. We could make the house bigger, but since the plot is rather narrow, and also for the reasons you mentioned, I would prefer to have everything "under one roof." And I’m afraid that if things like the sports and hobby room are planned in the upper floors, they will rather be rationalized away than if they are in the basement.

However, the negative points are also significant, for example I hadn’t considered the insurance aspect.

Did you consider back then choosing a closed water management system? I would initially think that this would lead to fewer surprises like suddenly higher groundwater levels.

Regarding the values you requested:



Drilling depths were 2x7 meters (same conditions). And a ram probing of 4m.

Distance to the neighboring plot would be 2 or 3 meters respectively. To the buildings 5.5 and 6 meters respectively.

How big is the plot? Could you live with raising the house including basement by 2-3 steps?

The plot is >1000 sqm but as mentioned narrow, the building width of approx. 9 meters we already fully use.

I had also already considered raising the building. Theoretically, the building regulations allow the basement to protrude up to 1.4 m, but as others have already pointed out, the ground floor is somewhat blocked by this. And to heap everything up to a hill might also look odd or probably be expensive.

Does the development plan specify a maximum number of storeys? So, for example, can you build two full storeys and then an attic, or does the development plan put a stop to that? If necessary, the classic with a larger garage and storage space there.