We use a key-locked 1 hour rated "safe" inside an antique fire-and-burglary rated large safe. The large safe is old enough that the original fire rating is questionable but it will pretty much eliminate the possibility of water damage to the modern papers "safe". But we really need to add a couple of fire-rated "safes" as the volume of items archived has grown exponentially over the kid years. Plenty of room for them in the big antique safe - it's just a piece of furniture not used for valuables storage, although no ordinary burglar would be able to crack it without a lot of time and neighbor-alerting noise and it's hardly portable at over half a ton weight. A safe-cracker would have it open in 10-20 minutes, but we're hardly a target for that sort.

But we also archive some important information electronically and copies of those are off-site.

There is no perfect answer.