Post-Apocalpytic Video games with world creation?

Looking for a post-apocalypse sandbox type game. Something similar to Minecraft but looks and plays more like Fallout. I want to be able to build my own bases, upgrade buildings for safe houses, that sort of thing. Anything out there?

From what I know, there are usually only Post Apocalyptic games with the ability to upgrade yourself and weapons. If you're interested there's this one game called Xsyon. It is Post Apocalyptic and sandbox. I'm sure you can upgrade things, but not to sure about doing the same with bases and safe houses.

There's state of decay. It's zombies. A little bit like both.

Sadly there aren't any games like that. I've been wanting this game forever