I have a 600lb gun safe. I am think about finishing out the attic space above the garage and making it a man cave/reloading room. I will add some thicker ply wood and some cross bracing. Anything else I should do to make sure it did not fall through the floor?

That's 600# safe plus how many firearms, any ammo? Probably need to double the joist, depends on the span and what size they are. If of to one side build a closet under it in the garage to help support this area. If not done right the safe could become a hood ornament!!

Make dang sure that floor can support the weight. For me personally, I would not put a gun safe upstairs

If you're dead set on putting it up there, I would make sure it is parked on top of a second floor load bearing wall, that is parked on top of a first floor load bearing wall. Getting it up there is gonna be a trick. But give a man a lever long enough and he can move the earth.

I had a 450-lb safe in the second floor of an apartment building, but that floor was designed to support the loads that come along in an inhabited space. Your attic wasn't. Beef it up like a real floor and you should be fine.

Jason has a good idea about putting it on or very near a load bearing wall. Those areas are significantly stronger.

Mine was upstairs and 550 pounds plus guns. My daughter and I put it up there. She is so proud of how we did it.
It set on a load bearing wall so it was not a problem. My biggest concern was if the stairs could hold it on the way up.
The only problem was after a few years I needed a bigger one. It is 900 pounds and downstairs. 900 pounds is pretty simple downstairs.

That last part, yep. Leverage is awesome

You must have competed in the Worlds Strongest Man competitions if you think moving a 450lb safe upstairs is easy. Mines just a tick over 700lbs and the 3 movers we hired had a heck of a time just getting it in the garage

True, but find a woman during her special time of the month and the safe will move itself!

My 65 year-old dad and I moved my 450-lb safe up the stairs to my apartment. I did the lifting. He just guided it up. Wasn't that bad.

Problem with a 700-lb safe is that the size gets really awkward too for a safe that big and heavy. The lighter/slimmer safes are easier because of weight and profile.

I asked the same question a few years ago about putting a safe upstairs. A few firemen chimed in to let me know that it's going to go through the floor if there is ever a fire

The idea is to never lift the safe. That is just too much work.
We made a block the same height as the steps. Then we simply tipped the safe up onto the first step, then tipped it up so we could put the block under it. Now it was setting flat again. Then we tipped it up to the next step, and moved the block up another step... all of the way to the top.

Note: I would not have done this with my new safe, it was too tall. Tipping it would have been scary after it got up a few steps. I am 6' 2" so I could handle tipping the shorter safe back toward me going up the steps. And this method may not work on all stairs, or for all (shorter) people.

We had ours on a dolly. Just rolled it up the steps basically.

^^^this

I wouldn't put that safe in the attic. Pretext: I've spent some years doing structural analysis and I generally tend to be a risk averse (ie professionally I can be a wuss) engineer at work. I highly recommend you NOT doing this for the reason patriot listed. I would say the only exception is if the spot in the attic is right up again a good load bearing wall. For example, the attic above my garage obviously has 4 walls. 3 of them are simply the outer garage walls. The wall up against the rest of the house is the main support wall for the upstairs.

Since you can see the beams:
What is the foot print of your safe?
Measure the spacing between the beams in your attic?
With the above 2, figure out how many beams you safe is likely to span in the position you envisioned placing it at. Remember, that plyboard is merely a covering. The beams are going to take and transfer to the load to the wall.
I assume your safe is wider than it is deeper. So choose an orientation that has the widest dimension of the safe span across as many beams as possible. Heck, get a piece of carboard cut to the exact foot print of you safe to layout the location that will distribute the weight over the most beams.

good luck.

I had my 450lb safe upstairs for awhile. Then I decided it was stupid and put it on ground floor.

My wife is about 400lb and she's never fallen through the floor. But she is probably wider than a safe.

Archimedes is your friend.

if only 2x6 joist spanning your garage on 16" or 24" centers. no

There's more to it than even what has been mentioned. Is it a stick built house or does it use engineered trusses? Most houses with engineered trusses are not built with attics meant to hold anything more than the roof. Maybe a water heater or air conditioner at most. Hell around here, the hole would never be big enough to get the thing into the attic anyway. Plus, I'm not sure I'd want the safe in a non-climate controlled space, especially if you attic ends up as hot as mine does!

$.02

It is walk in attic space that I am going to finish out and add ac ducts.it will have trusses put in.

Check the grade of lumber to see if it's load bearing quality. If the attic space was originally built only to be an attic space, I seriously doubt the joists are the higher standard.

I added trusses in the attic space above my garage when I decked it just for storage. While the ceiling joists were 2x12's, they were not for load bearing use.

There are also specific building codes regarding finishing out attic spaces, so check with your local office.

I would honestly get an engineer involved. If that safe came crashing down and hurt someone it would cost a ton to repair the house plus the damage to the person is not worth the risk.

Yes, you buy a safe to reduce risk or the potential for loss, and not to increase it.

not all load bearing walls are equal, the wall could have been constructed with 24"oc, so, I would definitely get some professional advice, I always doubled the studs, sometimes tripled when planning for a heavy load.