Hello everyone,
As mentioned above, this is currently the main question for us. I’m sure it has been asked many times before, but every construction project needs to be considered individually.
My wife inherited the plot of land from her parents.
Information about the plot:
- not yet developed
- 900m² (9,688 ft²) area
- street at the property has about a 3% slope
- the plot has the same slope where it borders the street
- the plot is located about 1.2 meters (4 feet) below street level on the north side (street side)
- the land rises towards the south/back, reaching street level towards the southeast and almost towards the southwest
- the sewer line is about 1.5 meters (5 feet) below street level
- approx. 60 meters (197 feet) west is the nearest intersection with electricity, water, and possibly sewer connection (more on this below)
- a 3-chamber septic tank is required WITHOUT a treatment pond. The pond is centrally located for the village
We have already had a soil inspection performed with two small percussion boreholes:
- Borehole one near the street at the lowest point: after 1.4 meters (4.6 feet) below the turf is buildable ground. Seasonal groundwater pressure starts at 0.9 meters (3 feet). So, 1.4m + 1.2m = 2.6 meters (8.5 feet) below street level is solid ground.
- Borehole two roughly in the middle of the plot: after 2 meters (6.6 feet) below the turf is buildable ground. Groundwater at 2.9 meters (9.5 feet). So, 2m + 0.7m = 2.7 meters (8.9 feet) below street level is solid ground.
In addition, we took some important height measurements, which allowed me to include the figures mentioned above.
The house floor plan would be about 40m² (430 ft²) larger if built without a basement. We would probably also need a garden shed or similar for the lawnmower, patio furniture, etc.
This would not be necessary if a basement is built.
A garage will also be built, but it will have a car lift, so it’s not suitable for storage.
The basement would ideally be a waterproof concrete box ('white tank') with appropriate insulation against cold.
Our estimate is that the basement would cost about 30,000 to 40,000 euros more.
What do you think?
Does having a basement make sense?
How much would you estimate the cost difference to be? (With and without basement)
Is it mandatory to install a sewage lift station with a backflow preventer? Or would it be possible to route the wastewater after the septic tank to the intersection in the west, so that a natural slope and height difference could be used?
What worries me most is the issue of wastewater and moisture in the soil and the associated additional costs.
Drainage, possibly a lift station.
Or should the 3-chamber septic tank be placed so deep that a natural slope is created?
How steep would the slope between the house outlet and the septic tank need to be?
The neighboring plots will almost certainly not be built on, so using them for excavator work should not be a problem.
I hope I haven’t forgotten anything.
Thanks in advance,
Joergi
As mentioned above, this is currently the main question for us. I’m sure it has been asked many times before, but every construction project needs to be considered individually.
My wife inherited the plot of land from her parents.
Information about the plot:
- not yet developed
- 900m² (9,688 ft²) area
- street at the property has about a 3% slope
- the plot has the same slope where it borders the street
- the plot is located about 1.2 meters (4 feet) below street level on the north side (street side)
- the land rises towards the south/back, reaching street level towards the southeast and almost towards the southwest
- the sewer line is about 1.5 meters (5 feet) below street level
- approx. 60 meters (197 feet) west is the nearest intersection with electricity, water, and possibly sewer connection (more on this below)
- a 3-chamber septic tank is required WITHOUT a treatment pond. The pond is centrally located for the village
We have already had a soil inspection performed with two small percussion boreholes:
- Borehole one near the street at the lowest point: after 1.4 meters (4.6 feet) below the turf is buildable ground. Seasonal groundwater pressure starts at 0.9 meters (3 feet). So, 1.4m + 1.2m = 2.6 meters (8.5 feet) below street level is solid ground.
- Borehole two roughly in the middle of the plot: after 2 meters (6.6 feet) below the turf is buildable ground. Groundwater at 2.9 meters (9.5 feet). So, 2m + 0.7m = 2.7 meters (8.9 feet) below street level is solid ground.
In addition, we took some important height measurements, which allowed me to include the figures mentioned above.
The house floor plan would be about 40m² (430 ft²) larger if built without a basement. We would probably also need a garden shed or similar for the lawnmower, patio furniture, etc.
This would not be necessary if a basement is built.
A garage will also be built, but it will have a car lift, so it’s not suitable for storage.
The basement would ideally be a waterproof concrete box ('white tank') with appropriate insulation against cold.
Our estimate is that the basement would cost about 30,000 to 40,000 euros more.
What do you think?
Does having a basement make sense?
How much would you estimate the cost difference to be? (With and without basement)
Is it mandatory to install a sewage lift station with a backflow preventer? Or would it be possible to route the wastewater after the septic tank to the intersection in the west, so that a natural slope and height difference could be used?
What worries me most is the issue of wastewater and moisture in the soil and the associated additional costs.
Drainage, possibly a lift station.
Or should the 3-chamber septic tank be placed so deep that a natural slope is created?
How steep would the slope between the house outlet and the septic tank need to be?
The neighboring plots will almost certainly not be built on, so using them for excavator work should not be a problem.
I hope I haven’t forgotten anything.
Thanks in advance,
Joergi
Papierturm9 Apr 2026 20:16Joergi schrieb:
- Borehole one near the street at the lowest point: buildable soil found after 1.4 meters (5 feet) beneath the turf. Seasonal groundwater pressure from 0.9 meters (3 feet). Solid ground 2.6 meters (8.5 feet) below street level (1.4m + 1.2m).
- Borehole two roughly in the middle of the lot: buildable soil found after 2 meters (6.5 feet) beneath the turf. Water encountered at 2.9 meters (9.5 feet). Solid ground 2.7 meters (9 feet) below street level (2m + 0.7m). Luckily, no one could see my face when I read this. Having buildable soil only two meters below the turf is usually not the kind of result you want.
If this is really the case, the question doesn’t really arise. So much soil would need to be replaced that you would essentially pay almost as much as for a basement.
In that case, you might as well just build the basement from the start.
(I’m usually not a fan of basements unless the plot is on a slope. This is one of the few exceptions.)
ypg schrieb:
You will get the same answers here as in the Green Forum. Normally not from me: I prefer to answer cross-postings only where direct communication is possible, and only there (to avoid duplication).
Exception: on the other channel, someone commented on an aspect I don’t want to leave unchallenged here:
Papierturm schrieb:
Ground suitable for building is normally found two meters (6.5 feet) below the turf layer. If that is really the case, then the question basically does not arise. So much soil would have to be replaced that you would almost end up paying for the basement anyway. In that case, you might as well build it right away. Replacing soil often causes new problems, similar to the expression "out of the frying pan into the fire." Soil replacement interferes with the water cycle and has become a popular measure recently, but I expect it will soon lead to serious political debates and strict regulations. There is no right to build on any piece of land you wish, even in times when suitable building plots are scarce. Whether it’s rice terracing areas or similar nonsense, these follies won’t stay popular for long (or realistically cannot).
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
Papierturm9 Apr 2026 20:37As an addition: It might also be possible to use pile foundations here. Overall, however, building on this site—whether with a basement or a slab-on-grade—will be expensive. You need to be aware of that.
Groundwater will be an issue both during construction and afterward.
Insulation... you need to understand that standard basement costs are for a utility basement, not a habitable one. The latter is significantly more expensive.
Development fees can also be considerable, depending on the municipality.
Honestly, whatever you plan to build, it will be costly.
Joergi schrieb:
The basement would ideally require a waterproof concrete shell (“white tank”) with appropriate insulation against cold.
Groundwater will be an issue both during construction and afterward.
Insulation... you need to understand that standard basement costs are for a utility basement, not a habitable one. The latter is significantly more expensive.
Development fees can also be considerable, depending on the municipality.
Honestly, whatever you plan to build, it will be costly.
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