Build a single-family house suitable for absence - what should be considered?

Yes, drainage to the outside is always the most cost-effective solution. Since you also mention that there is a lot of greenery present, insurance coverage over the areas should not be a problem.

Note to self. Learn a martial art before the next trip to Berlin.

I was there last week - I have never felt so safe. Without a fight. And it was very quiet everywhere, hardly any car city traffic, lots of public transport and hybrid taxis :)

Berlin is actually quite okay. Most people here get along pretty well with each other. But in a big city, stupid things can happen sometimes, and if you can protect yourself from that as best as possible, you should definitely do it.

Matthias

I have felt safe in Berlin so far, only now I am slowly having doubts.

Heating failure. A modern house does not cool down so quickly and anyway someone comes at least every other day to empty the mailbox and water the plants. That person can take care of it then.

With a pitched roof there is no stagnant water. Flat roofs are also watertight. The gutters should perhaps be regularly cleared of leaves.

If the sewage system cannot handle heavy rain, you probably can’t do much. There are flaps for the drain pipes that close when pressure comes from the wrong direction. Otherwise, there should be no wet feet, at most a stream nearby that likes to overflow its banks.

The discussion reminds me somewhat of the Safe House by Robert Konieczny.

I think one simply has to recognize here that the location and nature of the project do not match your need for security (whether this is even feasible at all, I doubt). Especially since the building is only intended to be occupied for a few weeks a year.