5/8 plywood flooring?
 

In the shop area I'm building off the back of my garage. Would it be ok to lay 5/8 plywood with 2 by 4's 12 inches off center? I got 5 sheets of this stuff laying around. I'm only gonna have my work bench, tool chest, TV, mini fridge in this area. And will be bolting compressor strait on the concrete.

I got a lip on the garage floor I want to get even with. I'm pretty sure ill kill my self if I trip over it:)

OK if you want a spongy floor. 2 X 4 will not be enough support, unless they are sitting on something

The 2 by 4's will be on the concrete slab.

Why do you want to build up the floor? Do you need to run something under there or match up to another area's floor height? Are you making it into a living space (heated/cooled)? If it's just to raise the floor, you can use pressure treated 2x4s every 16" on center. I would recommend 3/4" ply for the subfloor. If you plan to heat or cool the space, you need to prep the slab with a vapor barrier and insulation.

I am bringing the floor up to be even with the garage slab. I bought a celling mounted shop heater for the garage.

This area is only for my work bench and tools to free up space I the garage

OK--then 2 X 4 would be fine. Have to be treated though. Touching concrete - a non-treated will rot.
12 inch on center should give you a nice firm floor. Put cripples between them to strenthen, cut down noise when walking. Stagger them 4" on center.

5/8" ply is going to flex in a big way just walking on it. Even between 12" centers. If you can use at least 3/4" subfloor material. If you don't mind some flex in the floor, the 5/8" is still safe with the way you have it going in. But even a heavy tool box will make it sag between the studs. Maybe build up the area where the tool box and fridge will be with more 2xs under it.

I got a crap load of 2 by 4's so I can run cross bracing in the flooring. I just want to run the 5/8 if I can since I got it.

I wouldnt build a house with it,but it should be fine as you describe it.especially given the cost of things today.Putting a cheapo layer of plastic down first would aid in the moisture from the floor creeping up.

That's the way to do it. Just add a ton of support where the tool box and fridge will be. And like krabben1 said, use some plastic sheeting as a moisture barrier. Best of luck with it.

I'm gona pick up the vapor bariar tomorrow. And I'm using foam insulation for the walls.

Now I just need to find a good venting system for when I polish. But that's another day:)

Thanks for the input everyone!