Renovation costs

We have now gone through this whole story. Everything out and then new :-)
It will definitely be an exciting and thrilling time, but also very stressful.

It is important that you clarify as much as possible beforehand. And many surprises will come your way.
Make sure to keep enough money in reserve. We have easily used up our reserve :-(
But the house is now standing and we are living in it.

For example, I hadn’t questioned gas at all

You don’t have to. You also have to "learn to read" a forum when it comes to exaggerated individual statements or alleged experiences :)

Have you already talked to a bank / broker about the project?

I believe the whole financing topic is currently the smaller problem. Of course, it will then become a decisive factor, but realistically, I can't imagine any major problems. Equity capital is available in smaller amounts (after all, we are still young...), additionally some tied-up capital (for example, the kitchen in the current apartment could be sold to the next tenant for about €5000). We could contribute a lot of personal effort (also through the family – 3 of the 6 siblings live nearby), plus the entire purchase process is also supported by the family. In other words: before it fails due to equity capital, my father will buy the house himself and thus contribute equity capital again.

Since my wife is a teacher (civil servant) and as an IT specialist I’m also moving into the future with relatively low risk, I consider the financing feasible. We had financial advice for real estate about a year ago and back then established that we didn’t want to commit ourselves to €400 - 450k. But we would have gotten that with the corresponding equity capital. New advice relating to this project is expected next week.

It is important that you clarify as much as possible beforehand. And many surprises will still come your way.
Make sure to keep enough money in reserve. We easily used up our reserve :-(

Yes, I think so too... We would plan a 10% reserve, which we could spend on unimportant things (garden design or similar) if it doesn't get used. How high was your reserve?

But the house is now standing and we are living in it.

Congratulations! :-)

Since my wife is a teacher (civil servant) and I, as an IT specialist, also have a rather low-risk outlook for the future, I consider the financing feasible. We had financial advice for real estate about a year ago and at that time determined that we did not want to commit to 400 - 450k. We could have gotten that with corresponding equity, though. New advice related to this project is expected next week.

That was exactly the same for us. We first wanted to build new, but decided against it because the amount to be financed seemed too large. The bank would have financed it anyway, but I wouldn’t have been able to sleep peacefully.

Yes, I think so too... We would plan a 10% reserve, which we (if it’s not used) could spend on unimportant things (garden design or similar). How much reserve did you have?

I think 10 percent is too little. We had just over 20 percent reserve and it was nowhere near enough. But that also depends on us, as we executed many things at a higher quality than we had planned. Many ideas and wishes only arise when you are in the renovation phase and have dealt intensively with the subject. If something is to be done on the outdoor facilities, I would definitely plan for it now. Otherwise, it will be missing in the end.

I would always plan for the worst case and if money is left over, you will be happy. But a renovation is ultimately more expensive than you think.

In the end, it was still significantly cheaper for us than a new build :)

Okay, I’ll definitely take that as an idea for the financial planning.

Today, a subtle idea came to me. I originally wanted to expand the attic enough to fit either a children's room or a study (then for 2 people). Both would be super cool, but not cheap, since we would have to plan at least one large dormer, probably even a double dormer spanning the upper two floors.

As an alternative, the idea came to me to build a small annex that could serve both as a living room and as a carport/garage. The whole thing would be split-level (ground level, i.e., between basement and raised ground floor), which I think is great for living spaces.

The question is of course: Is it cheaper to attach a well-insulated prefabricated box to the house, or is a converted roof structure more affordable? That way, we would also create living space on the ground floor, which in terms of low barriers for emergencies/old age is certainly not uninteresting. From your perspective, are there any practical experiences or fundamental considerations that speak for one or the other?

I don't want to discourage you, but since March 21st, the clocks are ticking a bit differently.

Before it fails due to equity, my father will buy the house himself and thus bring in equity again.

You shouldn't approach the whole thing too naively. Taxes/fees might potentially be due twice, and banks prefer the owner as the borrower. Furthermore, there should be an open discussion about who has to bear which risks or takes on obligations.

A tip. Don’t just get advice from one banker. Especially because apparently your situation is not standard; they are not liable for tax matters.