Outbuilding as a basement replacement, are there legal issues?

I am currently planning a new building. For several reasons, I want to do without a basement (groundwater, costs, avoiding stairs). Therefore, I naturally need compensatory space. For this purpose, I have thought about an extension.

The extension should contain: laundry room, storage, if possible a technical room (is that legally possible?), and possibly a hobby room.

Now, an extension of the same quality as the main house is simply too expensive for me.

I have considered alternatives: For example, I contacted a dealer for concrete prefab garages. According to him, he also often sells outbuildings that are also insulated and can be used for this purpose. The "building" would then be thermally separated from the main house (by a door) but connected to the house. It would be equipped with 10 cm of styrofoam insulation. It has a flat roof that should be greened and possibly also partly serve as a roof terrace. It should also be equipped with windows, electricity, and heating from the main building.

If you ask a house-building company, they usually advise against it immediately and hold the opinion: "It won't be cheaper if you add the interior fittings."

I think that since basements can also be offered for well under 1000€/sqm and the quality regarding thermal insulation etc. does not have to meet the same standards, this should actually be a cheaper alternative.

My questions regarding this are:

[*]Is this legally and/or technically problematic?
[*]Is an outbuilding a privileged building, is it allowed to be built in the building setback areas?
[*]Would other technical solutions pay off, such as concrete prefabricated parts (individual walls instead of a finished "box"), in-situ concrete, massive prefabricated house parts like expanded clay, normal masonry, etc.?
[*]What are your experiences/opinions on this point?

I have already searched but have not yet seen a thread dealing with this topic. I would have thought this is a common problem when you want to build without a basement.

Thanks in advance,
Andreas

Hello,

The extension shall contain: laundry room, storage, if possible a technical room (is that legally possible?), and possibly a hobby room ... Now an extension of the same quality as the main house is simply too expensive for me ... For example, I asked a dealer for prefabricated concrete garages ...
When you ask a house building company, they usually advise against it immediately and hold the opinion: "It won't be cheaper if you add interior finishing."

The opinion expressed is correct. You can "only" save in this area if you build the extension yourself; for that your supplier has to pour the foundation slab, provide the structural engineering, and the rest is no rocket science ... if you forgo accessibility, which - by the way - is not allowed in the required 3.00 m setback area anyway, and you don't place it on the boundary.

I think you can also get a basement offered for well under €1000/sqm ....

Yes, I remember the advertisement ... there are then 4 unconnected walls (total of 50 sqm footprint) and nothing else ....

Is an outbuilding a privileged building, is it allowed to be erected within the building setback areas?

Since the extension must be insulated mandatorily, it is not allowed to place it on the building boundary. In case of uncertainties, the respective state building code provides information.

I have already searched but have not yet seen a thread that deals with this topic.

But you should already have learned a lot about setback areas

Rhineland regards

Hello,

the room is to be considered as a living space in terms of building regulations as you described and is therefore not privileged.

Therefore, the room itself must have a 3m distance to the boundary or must be secured by a building encumbrance on the neighboring property.

Exceptions confirm the rule, for more information I need plans from the builder.

Best regards
Dirk Grafe

Okay, thanks already for the information. Constructing the extension as edge development may not be so important and practical, as you then also have restrictions regarding windows etc., which would again counteract the purpose of better lighting.

After flipping through the building regulations, I only came to the conclusion that a building that does not contain living rooms falls under the category of a privileged building.

But even if I forgo the edge development, the problem of the very high requirements for insulation etc. of the extension remains. This does not necessarily make much sense for purely utilitarian space. Since you usually have to make financial compromises when building a house, I still see potential savings here if you can live with certain restrictions. Especially since in the targeted building area, basements are rather not recommended due to high groundwater pressure.

The mentioned precast concrete supplier also said that he frequently offers this solution. It makes sense from the consideration that I was offered a developed basement that is twice the size (of the house’s footprint) and costs far less than half, so the question for me is: a) Is such a solution permissible, b) if yes, what restrictions would such a solution involve — which rooms, facilities would not be allowed to be placed in the building, and c) what other cost-effective alternatives would there be?

I understand that if you want a living space like in a residential building, you have the same costs, but does that also apply to less demanding utilitarian space?

I have come to the conclusion after leafing through the building regulations that a building that does not contain any habitable rooms falls into the category of a privileged building.

If you want to know exactly, you have to look into the Landesbauordnung BB. In NRW, non-privileged rooms include, for example, technical rooms (heating) or an unauthorized use, i.e., if something is (permanently) stored in an attached garage that is not allowed to be stored there, the garage strictly speaking loses its privileged status due to the changed/not permitted use.

But even if I forgo the boundary development, the problem remains of the very high requirements for insulation, etc., of the extension. This does not necessarily make much sense for pure utility space.

That probably depends on what you want to store there.

Best regards Dirk Grafe