Cost planning - core renovation of farmhouse / country house

I visited my brother-in-law on Thursday. He and his wife bought a house in the south of Munich about 2 years ago. The main house is from 1949 and the extension from 1978. Since then, they have been renovating. The ground floor is almost finished and the upper floor halfway done. They have been living there since last year. Both are from the construction industry. She is an architect and he is a master painter with his own company.

Some walls were removed and steel beams installed, the step between the old and new building was retained, a suspended ceiling with a nice lighting concept, new electrical installation with KNX, dry screed with underfloor heating, staircase kept but completely refurbished (must have been a dirty job), ...

Much was done in-house and for the rest, they had many companies on hand that they work with in daily business. Despite a lot of in-house work, quite a bit of money has flowed into the project. The most important thing from their perspective was that whenever a company worked there, they were reachable and quick on site. There are simply many uncertainties in such an old building that are best looked at together immediately and decisions made on how to proceed.

These were now just some impressions of this project. Although I work as a product manager for interior construction products in commercial building, I wouldn't know if I would dare to take on such a project. Definitely only if I lived very close by.

I have also already considered wall heating.

I already said that I would consider it leaving the bounds of proportionality if you expected the house to be durable for more than 70 to 75 years. There is a bathroom here in the extension, and I also see it likely to remain that way, with reinforced concrete ceilings on any floor. Considering the year of construction, I would have also expected the house to have integrated bathrooms; in the so-called villa segment, those were quite common already. Are you actually sure that the mentioned year of construction refers to the core building?

The problem is, if you are not painlessly willing to do urban camping with a toddler for several years, you cannot renovate such properties that thoroughly. You cannot gradually install new heating, insulation, electrical systems, windows, floors. You can do that with buildings that only need cosmetic renovations.

Honestly, I am not sure if the two of them trust themselves to do exactly these basic works (except floors). I rather assumed interior finishing.

The most important thing from their perspective was that if a company worked there, they were reachable and quick on site. There are simply many uncertainties in such an old building, so it is best to look at it together directly and decide how to proceed.

I agree 100%. If the installer wants to drill through an interior wall and the drill with 1m is not enough, then it is definitely semi-good if you have 500 km travel. Even so, a 2-hour sink installation became a 2-day project.

Even so, what was supposed to be a 2-hour sink installation turned into a 2-day project.

Yes, I can confirm this experience as well. In an old building (ours is from 1935), projects that would take just a few minutes to hours in a newer house can turn into activities that occupy you for days.
This doesn’t have to be tragic; sometimes it’s just annoying or something you have to learn to live with.

To the OP: There is a website that I found quite informative when we modernized our house --> fachwerk dot de. Here you’ll find plenty of reading material that is quite interesting and informative without aiming to turn you into an expert. There is also a forum where, depending on your questions, you can get a rough idea of what might (but doesn’t have to) come up during an old building renovation.