ᐅ There is water on the building site.

Good drainage is important, but if the ground has been turned into a swampy bog over decades due to constant flooding, building there becomes difficult, often requiring pile foundations or similar solutions.

Drainage may also not work if an underground stream backs up during rainfall; you cannot simply redirect this water into the sewer system without proper permission.

I don’t want to be alarmist — in the end, it might just be surface water from neighboring properties that struggles to drain through the clayey, loamy topsoil and collects as puddles on the surface. Beneath this layer, there could be suitable building ground. Additional costs for extra excavation in such cases are usually minimal and not worth worrying about.

On our property, water also accumulates because the soil is interspersed with clay layers. A soil report showed no groundwater in the basement area. There was also no water in the excavation pit, which was about 3 meters (10 feet) deep. However, the original soil was not allowed to be used for backfilling but had to be replaced with compactable material, which was not exactly cheap.

It might not be a big issue, but building without a basement could be advantageous. Ask the neighbors if they have experienced major problems with settlement cracks or similar issues. Also, check if there is a soil survey available. You should plan for some extra budget to cover additional foundation work and earthworks.

I would not rely on the soil report from the neighbors. We have a relatively large plot of land (just under 2000 m² (21,530 sq ft)) and had several boreholes drilled because in the front section the groundwater was already at 2 m (6.5 ft), so we decided to build in the rear section.

If it’s clay soil, water tends to accumulate. We also live on clay. In fact, some local place names even include “Lehmberg” (Clay Hill). Infiltration isn’t possible. A stormwater drainage system is necessary, which is available here and connects roofs and drain pipes. It discharges into the lake. In that case, no basements should be built! Also, avoid sealing too much additional ground surface. It’s better to have plenty of plants or gravel paths instead of paved areas. That way, you can manage it well. Nevertheless, we preferred to avoid features like flush-mounted terrace doors and similar elements because of heavy rain and snowmelt. K.