ᐅ Building plot with buried old cellar

Hello everyone,

We have now reserved the plot mentioned in the https://www.hausbau-forum.de/threads/3-geschossig-nach-34-baugb-gerechtfertigt.12413/ and are focusing more intensively on building the three-story house (more on that in another thread). The housing company from which we would buy the plot had a multi-family house on it that was demolished. During this, the basement was excavated and then backfilled. However, the walls (I assume the exterior walls or all load-bearing walls?) were not part of that and probably remain. Buyers of other plots, where demolition of the existing houses had also been commissioned at the time, were already surprised to find construction debris deposited there. For this reason, they advised us to have a soil survey (or a shallow investigation => what exactly is this?) carried out (already during the current reservation phase).

What should be considered regarding this? From what I have read, a standard geotechnical site investigation does not necessarily include a contamination survey. However, that would certainly be advisable in this case, right? It is generally recommended here, especially since arsenic and heavy metal content are often elevated due to historic mining activities.

So far, we have no (specific) idea exactly where our house will be located (but quite close, as we are supposed to build directly adjoining the multi-family house on the neighboring plot). Does it make sense to clarify this first, so that the boreholes can be made exactly along their outline, or does the exact position not matter that much in the end and we could already commission the investigation?

Regarding the neighboring plot, another question. From what I have read, when building on or very close to a boundary line, you need the consent of the owner of the neighboring plot. Does this also apply in our case, even though the city (without a zoning plan or planning permission) requires a closed building structure?

Thank you in advance.

globetrotter schrieb:
One more question regarding the neighboring property. From what I have read, when building on a property boundary, you must obtain the consent of the owner of the neighboring property. Is this required in our case, even if the city mandates a continuous building line without a development plan?

No. If the city requires a continuous building line, the neighbor’s consent is not necessary, unless this continuous building line conflicts with existing planning regulations. If your neighbor objects to your building permit application or to the continuous building line, they must take action themselves by filing an objection or lawsuit. Such legal action would not be directly against your permit application but against the city’s justified and general regulation mandating the continuous building line, as this requirement applies not only to your project but also to other construction proposals, should you decide to withdraw yours.

In principle, it is theoretically possible that in five years, the city might decide that the continuous building line is completely inappropriate and instead require a detached building style—then you or other prospective builders would have to ask the neighbor for permission to build attached. However, given the existing development, this would be quite unusual. For me, this would immediately and significantly decrease the property value to the point where I would either have to acquire the land under the condition of a detached building style for very low cost or look for another property.

Best regards
Dirk Grafe

Hello everyone,

thank you for the response. Are there any recommendations regarding the general procedure for soil investigation? For example, should a preliminary soil report with estimated values be prepared before purchasing the plot, based on the likely location of the house? And in addition to the standard geotechnical survey, is it advisable to also carry out a contaminated land assessment (which apparently is not always done)?

Best regards

The soil survey should always be conducted BEFORE purchasing the property.
If there might actually be a partially buried basement containing hazardous materials like asbestos and similar contaminants, the plot could quickly turn from a bargain into a money pit. Such hazardous waste removal is expensive. If you already know where you want to build, the soil survey can be more detailed, and you can receive foundation recommendations. I would also recommend a contamination assessment. It’s better to invest around 1000 € (approx. 1100 USD) here and possibly withdraw from the contract than to have to deal with potential risks later on.