Renovation or demolition and new construction - decision support from the architect?

Renovation for 3500€/sqm must have some special features?

There is always a bit of a lack of reference as to what is considered standard and what is a special feature.
We also covered the two points you left out, for example external insulation, sealing, and insulation of the basement. Additionally, the statics. Several steel profiles were inserted because the house really has poor building fabric. I personally also found the dismantling very expensive.

We have a mix of renovated old building and new construction; I never separated the individual invoices. But I can’t think of any trade where we were cheaper in the old building than in the extension. For example, in the old building, we needed a very expensive special screed that is very thin because otherwise the room heights would have been too low. Therefore, we also needed a shallow, electric system for the underfloor heating in the bathroom. The extension just has the standard there.
We also have large-format tiles in 120x120 and partly air conditioning, which drove the price up.
On the other hand, in the bathroom, we have “only” Vigour and the staircase is a double-stringer staircase with finger-jointed oak. So some things are rather average as well.

Interesting, did you already know from the start that it would be a renovation for you?

Yes. The house was from the 1930s and almost in its original state. Also, it is a semi-detached house and shares the ridge with the other semi-detached house – you basically can’t demolish it individually. By now, many houses in the whole settlement area have been renovated (I estimate 80%), all individually, and none resembles the other anymore. We especially liked that, combined with the large plots in a central location, so we deliberately plunged into this adventure. Good that we didn’t know beforehand what all would come our way!

So we could have alternatively built in a new development area, but we definitely didn’t want that.

Here’s already a photo from outside:

That’s beautiful; I wouldn’t tear that down.

great house! I would find leaving very sad.

Exciting, did you also know from the beginning that you were going to do a renovation?

Yes. A new build of the same size would have been MUCH more expensive (200 sqm + basement --> ~750-800K € including additional costs kitchen, terrace) compared to renovation (~420K € including additional costs, kitchen, terrace) – we simply couldn’t afford that after purchasing the existing property. Additionally, the building structure was good and the renovation had the big advantage that we didn’t need a building permit (no changes to the building envelope). And I also belong to the faction that finds the spatial feeling in an old building much more pleasant.

The only thing that currently really bothers me is the relatively damp basement. That was never a problem during construction/inspection, but only this year in summer. We suspect that the groundwater level is now much higher than in 2022/23. We had the wettest winter/spring on record here, and 2022 was a drought.

Now in summer, we run a dehumidifier continuously during the day (8 a.m. to 6 p.m., keeps humidity <60%), which basically runs for free because of our photovoltaic system. In winter it’s no problem. Long term, sealing wouldn’t be bad, but financially it hardly pays off. Even if I run the dehumidifier at 300 € per year permanently, it would take ages to be worthwhile. The moisture mainly comes from below; maybe one can apply sealing slurry or something like that there, we’re still thinking about it.

Otherwise, we have a really great living standard here. Thanks to the renovated roof + photovoltaic as additional sun protection on the south side, it is really bearable in the attic even at 35° outside temperature. We have 2 full floors + attic, which I really appreciate (=children’s rooms, bedroom, bathroom on the upper floor completely without sloping ceilings) – you hardly find that in new builds. So far no problem in winter with the heat pump either. Electrical systems and wiring are up to new build standard, etc., and at the same time many beautiful old elements were preserved (oak staircase, doors and frames, old sliding doors, etc.).

There is also a thread about this here:

Only one photo, but slowly a trend towards not demolishing. Please more basics. Photos and plans.

Thank you very much for your further feedback.
I wanted to provide additional photos and also tried to draw the floor plan.
It’s my first time using the program, so the stairs are improvised with arrows...

Basement (outside stairs going up on the left):


Ground floor (three entrance steps up in front of the house):


Upper floor (with sloping roof on the west side at the top and on the east side at the bottom, going down to approx. 1.5m):


The external dimensions are correct, but there may be deviations in scale inside because the numbers on the original are hard to read. The dimensions of the external walls were apparently "corrected," so they were readable and should be accurate (in the basement 24cm, on the ground floor 28cm except on the south wall, where it’s 36.5cm. Interior walls 11.5cm.

Here are photos of the rooms from the viewing back then; the seller has since cleared out all the items.

Basement (laundry room):


Ground floor (bathroom, kitchen, living room)


Upper floor (bathroom, bedroom, child1)


What else we know:
- The roof was apparently redone about ~30 years ago.
- The ground floor bathroom was made barrier-free about ~10 years ago.
- The oil heating system is >30 years old, so a replacement will be necessary for us sooner or later.

I hope this provides enough basis for discussion. If not, please don’t take it amiss — I’ll try to provide more later.

The only thing that really still bothers me right now is the relatively damp basement. That was never a problem during the construction phase or at the viewing but only started this summer. We suspect that the groundwater level is now much higher than it was in 2022/23. We had the wettest winter/spring here since records began, and 2022 was a drought.

We now have a dehumidifier running continuously during the day (8 am–6 pm, keeping humidity <60%), which practically runs for free thanks to our photovoltaic system. It’s not a problem in winter. Long-term waterproofing wouldn’t be a bad idea, but financially it hardly pays off. Even if I run the dehumidifier permanently for €300 per year, it would take ages to recoup. The moisture mainly comes from below, so maybe it’s possible to apply sealing slurry or something there; we’re still thinking about that.

Oh, that sounds surprising. Our basement is dry, groundwater seems to be an issue here in the area too — but we were proudly told it’s never been a problem thanks to a slightly higher elevation.

Otherwise, we also have a really great living standard here. Thanks to the renovated roof and the photovoltaic system as additional sun protection on the south side, it’s quite bearable in the upper floor even at 35°C outside temperature. We have 2 full stories plus the attic, which I really appreciate (=children’s rooms, bedroom, bathroom upstairs completely without sloping ceilings) — you rarely find that in new builds. So far, with the heat pump, there have been no problems in winter either. Electrical wiring and systems are up to new-build standards, etc., and many beautiful old elements have been preserved (oak staircase, doors and frames, old sliding doors, etc.).

I’m glad to hear that you’ve achieved such a great living standard. Also, that you use photovoltaics and apparently can cover your electricity needs so that there’s something left for the basement fan is great.
Thanks for the link; I’ll read through the thread when I have time.

What I forgot (was too slow editing): The house has a 3m distance on the left and a 3m carport on the right. The garden faces west and can be accessed from the living room via a terrace.