My house was built in 1952 and it has a wood floor that is around 2"-3" thick w/crawl space that I can easily access - with about 4' of space between the ground and the floor.

I have the safe in the closet and I plan on bolting it down with grade 8 bolts and using 2x6's under the floor with about 6" or so extending past the safe on both side like so...



My main question is and perhaps I am over thinking this but... Should I bolt it down with the threads facing up or down? Meaning should run the bolts from the floor up - tighten the nut inside the safe or run the bolt facing down from inside the safe - tighten the bolt from under the floor?

Any other ideas on how I should re-enforce the area I bolt the safe to under the floor... I thought cross sectioning the 2x6's kinda like the pic below or using about 4x4's but thought that was maybe a but much. I am not worried about the weight of the safe however as it is somewhat light... Probably a bit less that 500lbs loaded.



Thanks!

Where are the existing floor joists in relation to that closet?  If it was me, I would run 4 lengths of all thread to a cross member under the floor joists and washer / nut them in place there, and again inside the safe.

It would be harder for someone to unbolt it if the nuts are inside the safe.

I would recommend using sections of angle iron (actually A36 steel) instead of 2x6 dimensional lumber. Softwood simply doesn't have much pull out / crush strength over the small area under a washer. It would also be fairly easy to saw apart the boards or split them apart the 2x6s with a framing hammer. If you don't want to use angle iron then consider 4x6s or at the minimin large washers. Also as leo84 pointed out, run the bolts up and put the nuts inside the safe.

In your situation, I used angle iron and all thread with nuts welded onto the bottom end of the all thread. I also sleeved the all thread in steel tubing to make it harder to cut with a reciprocating saw.

That is a great idea with the angle iron! I believe I am going to go that route.

Weld a blob of bead on the threads.  Google welding with batteries if you have no welder.  You could even beat on the bolts to booger up the threads too. Grade 8 is more brittle than grade 5. I'd use grade 5 bolts.  

I would add a seismic sensor on the safe connected to an alarm system. That way if anyone tries to move the safe, cut the bolts, etc the alarm will be triggered.