You might also consider some lags into wall studs as well as the floor.
You might also consider some lags into wall studs as well as the floor.
Just because something is legal to do doesn't mean it is the smart thing to do.
There are 2ft by 3ft cement boards meant to be installed with/under tile, I am drawing a blank as to their name but will have some limited fire resistance, not be harmed much by moisture and can be as thin as 1/4 of an inch to reduce the amount of space between floor and safe in regards to avoiding pry bar attacks. Also a bit more durable than drywall, but if you can protect its edges or protect that space between the safe, the cement board, and your floor you will have a relatively safe option that protects safe from floor and vs versa. I am sure there are more durable alternatives, but the cement board should be less than 10$ for a sheet if not less than 5$. I know you can go crazy over the top with Kevlar/fiberglass 4x8 sheets but that's not cost realistic or necessary. Especially if you can find a way to protect the seam between safe and floor, maybe mount some angle iron 1/4" thick straight to the floor with the angle riding up to the bottom of the safe, I guess the big thing is making it take long enough that it isn't worth the time/risk.
Beware of some pressure treated wood. That stuff + steel can equal rust/corrosion.
Never, under any circumstances, consume a sleeping pill and laxative on the same night.
Very true, and applies to some OSB board adhesives as well. Regular plywood 'painted' with linseed oil (to prevent board rot) has worked well for over 25 years under several safes I have moved recently.
Pry bar issue seems to be theoretical, rather than real. Should be fairly easy to drive a pry bar shoe under a safe sitting directly on the floor, or at least not much more difficult than driving a pry bar shoe under a safe mounted on a board. Millwrights usually elevate the edge of a heavy object by hammering a cold chisel in to create space for the pry bar shoe or toe jack.