Old building renovation (1966): Two-family house - floor plan sketch

In my opinion, a facade renovation would be pretty much the first thing I would do.

For a multi-family house from 1966, it is probably sensible to tackle something like that, but not the first measure, as there are other measures that are cheaper, easier to carry out, and more efficient.

Much more important:
Windows (are from 1998, so already done)
Insulate the top floor ceiling for €12/m² non-walkable or €40/m² walkable -> peanuts and little work, the U-value drops from 1.5 to 0.1-0.2 W/m²K
Insulate the basement ceiling for €20/m² -> peanuts and little work, the U-value drops from 1.5 to 0.2 W/m²K
Depending on the age, convert the heating to renewable energy technology -> 10-30% savings

Facade renovation: significantly more difficult to do yourself than insulating the floor and basement ceilings. Material probably around €30/m², but a lot of work and therefore expensive. Professionally done costs €100-150 /m² and the U-value only drops from 1.5 to 0.2 W/m²K
1960s multi-family houses sometimes already had U-values around 1.0 depending on the wall construction - so the benefit is even less.

There are nicer things than explaining to a single child (whose two siblings do not yet exist, in a house with room for four more children): vacation (except on the balcony / rooftop terraces) is out of the question, mommy and daddy find tenants so annoying that they prefer to heat a half-empty three-family house.

The little additional costs (please imagine them sung in the mind's ear by Johanna v. Koczian) add up to the equivalent of a great family year's vacation at its finest.

And it stays with the old jalopy because the leasing rates for something new are not affordable.

Even with a million inheritance plus extra payment, I would never think of living in a threefamily house with three persons.

Not all tenants have a rat on their shoulder, cook spoiled meat, and tear off sinks at night ;-)

In principle, I can understand if someone wants to live alone in their house. What I don’t understand at all in this context is why someone then buys a three-family house.

Wait a minute: I could still understand if someone says: awesome plot, I’ll tear down the shack and build myself a top-notch single-family house! But doing an elaborate renovation (even if the layout now does make sense), accepting a fortune in additional costs, and then in the worst case not even managing with one child? And honestly: the house isn’t even that nice that I would suspect a spontaneous love at first sight as the trigger...

But whatever, the OP wants it that way, we don’t have to understand that. I find Till’s suggestions very valid and would definitely go for that. For me, the façade before moving in would rather be because it’s really terrible to live in the building under renovation during a façade renovation (I speak from experience, I’ve had to spend a summer behind plastic sheeting...). And something like that isn’t done in two or three weeks.

... does it always escalate this quickly here? ;-)

So basically, this was about the constructive criticism of the floor plan ... You guys have somewhat strayed from the topic. The reasons for taking over the house / property are rather family-related and have no place on the internet. The whole house also has a great emotional value. But I would prefer not to go into that in the vastness of the internet.

Rather to the facts. Correct - the stairwell is indeed quite difficult to integrate into the living space, but we can manage that. I don't see that as a problem. Of course, the entire project will never be able to "keep up" with a perfectly planned house when it comes to all these topics. The charm will come from a completely different direction. The basement is in great condition - like basically the entire house! In principle, my parents lived in it until recently and you could just redo some wallpaper and laminate flooring and move in - done. But we are now taking the opportunity and investing some money in the renovation. The attic floor has already been insulated - we are now refining that a bit in connection with the new roof and making a proper separation between warm and cold areas. At the same time, the insulation of the basement ceiling is also planned. The heating system is now almost 15 years old but throwing it out would currently still be a waste of money. The boiler was replaced 4 years ago. We are now renewing the pipes and the old radiators will be removed. Heating niches will be bricked up. All glass blocks will be removed and replaced by new windows or bricked up in the stairwell and windows installed. Along with a new front door. But now I have somewhat strayed from the actual topic of the floor plan.

The additional costs are quite high - that is correct. I have calculated these with the mentioned 750€. You can find more details here -> And yes - very likely the number is somewhat overestimated, but it is always better to calculate a bit more. What all this about the floor plan has to do with our vacation plans, cars, etc. I don’t know - I would prefer to leave that uncommented here.

So - is there any more constructive criticism of the floor plans now? The previous critiques were very well received at our home!

... does it always escalate so quickly here? ;-)

I would say: YES. ;)
As they say: high involvement product.

What has been annoying me all this time is the passage between the newly chosen bedroom and the new baby room to the terrace. It is simply stupid. But so far, I haven’t come up with anything elegant for it... *keeps pondering*

Currently, this hallway does not even exist. Currently, the planned bedroom is still a living room, which simultaneously serves as a passage room to the terrace. We find a passage room to the terrace bothersome in all constellations – therefore, we have tried to redesign the corridor and thus create access to the terrace. However, we do not find this solution all that bad ...

Creating access from under the terrace or outside is simply too complex.