I don't have much basement experience, but if your house had a total fire, wouldn't quite a bit of the burn essentially fall down into the basement?
Consider covering your two new walls with two layers of firerock. Whatever you make the ceiling out of be sure it's strong and you could shield it with firerock as well. Use a good metal door and lock to secure the room. Buy a good safe and put it in the room, the room will act as a buffer to the fire while protecting your safe and buying you more time for fire protection. I've got some first-hand experience with fire and safes, I will be posting a thread about it in the future.
BTW the de-humidifier will either need to drain in a floor drain or collect in a container to be emptied by someone regularly.
Here ya go: Smith Security Vault Doors and Gun Safes .
I bought a safe from Doug Smith, the owner. He lives about 2 miles from me. He's well known throughout the US. Does outstanding work.
If you use block for the walls, make sure you paint the floor and walls with Drylock to seal out moisture.
Outer wall if block construction is a weak point. No concrete ceiling is another. Just for starters. If inner wall is block, it most be back filled with rebar and concrete.
yea, after looking into it some more i changed my mind some.
Doing a real fireresistant vault/safe is just way too much money. I think instead I will go with a general 'strong room'. Probably plywood and metal. No block, no fireproofing, and then just get a small fireproof box for the papers.
May upgrade later but for now the pricetag on a real vault is just too high
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I've considered lining a walk-in closet with some of this stuff. Doors are available too I think, have not checked that yet though.