ᐅ Demolition or Renovation? Seeking Advice for Basements from the 1970s!

Hello everyone,

We are in the process of purchasing a house built in 1973 and are now facing the question of how to handle the basement. The house itself is not worth preserving. We are wondering whether to rebuild completely or if it makes more sense to keep the basement and build on top of it. We hope that renovating will be more cost-effective and allow us to gain more living space.

Since we are not experts, we wanted to ask for experiences and advice here in the forum:

• Check the condition of the basement:
At first glance, the basement looks solid, but of course, this is just a non-professional assessment. From your point of view, what are the key steps to get the basement’s condition professionally evaluated? Should we contact a building surveyor or a structural engineer directly?


• Renovation or demolition:
Does anyone have experience with whether it is more economical to renovate the basement or to demolish it completely in such a case? Are there typical issues with basements from the 1970s that we should be aware of (e.g., structural concerns)?



• Experience with similar projects:
Who among you has faced a similar decision before? What was decisive for your choice – and in hindsight, would you make the same decision again?

I look forward to your experiences, advice, or tips on what else we should consider. Any idea helps us make the right choice for our project!

Thank you in advance and best regards

Skyhawk172 schrieb:

We are in the process of purchasing a house built in 1973 and are now considering how to deal with the basement. The house itself is not worth preserving. We are wondering whether to build new or if it makes more sense to keep the basement and build on top of it. We hope that renovating will be more cost-effective and allow us to gain more living space.

I’m happy to respond to your three questions—ideally after you share the existing basement plans from the building file (even if you don’t intend to use it) along with the details of the house standing on it.

To save you from searching through my many posts on the keyword “existing basement,” I have compiled a library for you—partly sorted by relevance, partly including links to multiple related posts and threads:

https://www.hausbau-forum.de/threads/fertighaus-ueber-alten-bestandskeller-bauen.24346/
https://www.hausbau-forum.de/threads/grundstueck-mit-altem-haus-zum-abriss-kosten.25642/
https://www.hausbau-forum.de/threads/grundrissentwurf-fuer-220m-einfamilienhaus.24702/page-17#post-213746
https://www.hausbau-forum.de/threads/angebot-ueber-ytong-bausatzhaus-bau-auf-bestehenden-keller.39957/page-2#post-514506 https://www.hausbau-forum.de/threads/neubau-massivhaus-auf-bestandskeller.41443/#post-531551
https://www.hausbau-forum.de/threads/abriss-eines-alten-keller-1970-kosten.41457/#post-531857

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In most basements, structural issues are unlikely. There are two common problem areas:
* Moisture caused by missing or damaged waterproofing or drainage – this can be fixed by excavating.
* Lack of insulation – this can be addressed on the exterior walls by excavating, but not under the slab.

The main question is whether the floor plan and ceiling height are suitable and what you plan to use the basement for. Demolition will probably be more expensive than building a new house on a greenfield site.

Grundaus schrieb:

In most basements, there is unlikely to be any structural problem. There are two main issue areas:
* Moisture due to missing or damaged waterproofing/drainage — can be fixed by excavation
* Lack of insulation — can be fixed on the exterior walls by excavation, but not under the slab.

The question is whether the floor plan/room height suits your needs and what you want to do with the basement. Demolition will probably be more expensive than building a new house on a greenfield site.

I assume a structural engineer is still necessary? What costs should I expect for that? I have seen figures around €5,000 (approx. $5,400) for a structural review here on the forum.

I am not aware of any damp spots. The basement is not insulated, typical for its construction year.

• Exterior wall is 30cm (12 inches) thick
• Sits on 40cm (16 inches) strip foundations
• The shell height should be about 2.50m (8 ft 2 in), rooms about 2.40m (7 ft 10 in) - I would make them higher in a new build, but this seems acceptable.

I now believe that demolition and rebuilding will be significantly more expensive.

• Demolition costs at least €20,000 (approx. $21,600)
• Only makes sense if it’s a habitable basement, including finishing around €2,000 (approx. $2,150) per square meter (sq m)
• New connection fees and potential surprises, higher incidental building costs, and the garden/land may be affected…
• For 140 sq m x €2,000 = €280,000 + €20,000 demolition + X = €300,000 + X
• Added value: Higher ceilings, everything from a single source, lower heating costs, current standards.
• €300,000 versus renovation, possibly adding external insulation and new windows — I claim I would come out considerably cheaper this way.
• Saving €100,000 corresponds roughly to a monthly loan payment reduction of €400 (approx. $430), which you would never spend on heating costs anyway.

Is there a flaw in my reasoning?

A key point: What needs to be done to the basement ceiling before new construction can be placed on top? Insulation — anything else? Costs?

Is it possible and allowed to continue using the "old" oil heating in the basement while installing a heat pump in the upper floors?

11ant schrieb:

I am happy to address your three questions—ideally after you have shared the existing basement from the building file, as well as the house built on it, even if you do not intend to use it.

To save you the effort of searching through my numerous posts on the term existing basement, I have compiled a library for you—partly sorted by relevance, and some include links to several other related posts or threads:

https://www.hausbau-forum.de/threads/fertighaus-ueber-alten-bestandskeller-bauen.24346/
https://www.hausbau-forum.de/threads/grundstueck-mit-altem-haus-zum-abriss-kosten.25642/
https://www.hausbau-forum.de/threads/grundrissentwurf-fuer-220m-einfamilienhaus.24702/page-17#post-213746
https://www.hausbau-forum.de/threads/angebot-ueber-ytong-bausatzhaus-bau-auf-bestehenden-keller.39957/page-2#post-514506 https://www.hausbau-forum.de/threads/neubau-massivhaus-auf-bestandskeller.41443/#post-531551
https://www.hausbau-forum.de/threads/abriss-eines-alten-keller-1970-kosten.41457/#post-531857

Attached are the house, basement, and foundation. I still need to review the building file.

Thank you very much for the compilation; I am working my way through it. It would be interesting to learn how the actual implementation went.

Skyhawk172 schrieb:

The house itself is not worth preserving.

Isn’t it an AB Elementhus, for which there is a thread here with good discussions among buyers renovating similar models? What is the reason, in your case, to avoid this approach?

Skyhawk172 schrieb:

Attached are pictures of the house, basement, and foundation. I still need to review the building file.

Picture 2 of the basement and the cross-section would benefit from including the upper dimension line as well as higher contrast on the dimension lines in general.

Skyhawk172 schrieb:

It would be interesting to hear how the project was carried out.

@Seven1984 completed a house https://www.hausbau-forum.de/threads/rohbaukeller-fundament-steht-10-jahre.33055/, although their case was different since the basement was not attached to an existing house; @OlliQueck https://www.hausbau-forum.de/threads/grundstueckskauf-auf-dem-vorher-ein-haus-abgebrannt-ist-was-beachten.35388/ bought a plot with a basement and a cleared burned-down wooden house; and @Mal Bauen https://www.hausbau-forum.de/threads/grundriss-neubau-auf-bungalow-bestandskeller-1-5-geschossige.44686/ had a basically good used house, but its extension was not economically viable due to structural weaknesses (of the house, not the basement). As far as I know, his project is not finished yet but he has decided how to proceed with the new construction. So, one case (33055) is completed, one case (35388) I’m not sure how far it has progressed, and one case (44686) might be well advanced but is not fully documented here yet.

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