Germany has more castles than the United States has McDonald’s. This is the Eltz castle, located in Wiershem. It has been owned and occupied by the same family for 33 generations over 800 years

[u/The_Love-Tap]

[u/sth128]

Are they legally obligated to keep the structure in its original material and interior design? Can they retrofit modern insulation, waterproofing, and adjust the interior so it's more like a modern home?

What's the major maintenance item for such castles?

[u/Groot_Benelux → u/sth128]

Are they legally obligated to keep the structure in its original material and interior design? 

Depends on the country. It's not unheard of that you need to fit some council or departments old expensive construction methods. Replace oak beams with oak beams ,etc

[u/orangeyougladiator → u/sth128]

You can do whatever you like to it, it’s yours and the land is as well. But it comes with lots of renovations and maintenance requirements because they aren’t rated for building houses in the new era of things. Couple that with no proper infrastructure support from your county, all the hassle it takes to live in one doesn’t equate to just building your ideal home new somewhere.

[u/Groot_Benelux → u/orangeyougladiator]

Depends on the place. In France the fact that you're supposed to keep it original (which has a huge repair pricetag) is why some of them are so cheap.

[u/215ls → u/orangeyougladiator]

Tell me you've never been to Germany without telling me. You can't even chose the kind of fence you want to have arount your frontyard. Bebauungsplan chooses for you. And with old buildings there's Denkmalschutz too. You don't want that on top

[u/ConnectionWild3381 → u/215ls]

so true

[u/Illustrious-Wolf4857 → u/sth128]

If it's a listed building, you are very limited in what you are allowed to change. I worked on one as a teen and we needed quite a few specialised craftspeople to find acceptable (and affordable) solutions. And about fifty part-time helpers for the unskilled work.