pros and cons of putting a osb floor in over cracked un even concrete

[cody michael]

I am considering putting a floor in over my cement floor in my wood shop, it is an old barn, the floor is pretty messed up, I was thinking 2x4's on the cement, shim them with wood or quickcrete where there is decent gap, then 3/4 osb, I probably have enough 2x4's so should only cost 150-200. the benifits I see are, I could put some insulation down to make it warmer, hopefully prevent some moisture condensation on tools (I have had this really bad in past years, but I have the wall insulated so hopefully that will help) smooth surface for walking and rolling tools. easier cleanup of wood shavings etc. also I may put a few runs for the dust collector in between the 2x4s, this would increase cost, but be very handy.

are there any cons I am missing? I have about 11ft ceiling so height should be okay.

[roger wiegand]

When I converted my barn to woodworking the floor was a nasty mix of concrete, asphalt, and dirt, all saturated with 100 years of oil. I dug that out, disposed of it properly, then poured a new concrete slab (with vapor barrier and foam insulation), put down 2x4 sleepers on their sides, 3/4" plywood subfloor and hardwood flooring. Having a wooden floor has been a delight after years of working on a concrete basement floor. Aside from a little time and money there are no downsides. I didn't have the overhead clearance for dust collection under the floor, but I did run wiring to floor outlets.

I'd worry about one layer of 3/4" OSB being stiff enough to properly support heavy tools.

[Don Jarvie]

3/4 OSB can carry plently of weight. If there's an area where there wil be heavy tools add some extra sleepers.

use wooden shims instead of cement. The cement could crack and grind up over time. A wood floor made my shop 100% warmer. Before I could feel the cold coming up from the concrete.

[cody michael]

my current heaviest tools are my 20 inch planer, around 7-800 and my unisaw, At some point I am planning on putting the planer on casters, if I did would that cause any issues? to have 200 pounds on 1 wheel? it will mainly be in one location so I could easily add extra 2x4's in that spot

[Jim Andrew]

You are going to lay the boards flat, so at 16" oc, you would have 12 1/2" between the boards. OSB flooring is made to span 24" in a house, so you could go with wider spacing realistically. If you could lay out and put a few extra pieces under the planer and saw, should be good. I laid my flooring at 19 3/16" oc, in my addition. Used 1z6 barn flooring, and is plenty solid. I laid extra pieces of 2x4 under the pallet rack where my plywood is stored. The spacing I used takes 5 boards per 8' versus 6 for 16" centers.

[cody michael]

I may do the 2x4 upright, to make space for a few runs for dust collecter, to other side of shop, maybe one to near the tablesaw so I don't have to step over it.

[Jim Andrew]

Does this barn have a foundation, with a sill plate? If so you could use joists to build a platform floor and not have to support it off the uneven concrete. You would have to build it heavy enough to support your machines, but not all that hard. Then you would have plenty of room to go under it with your dc system. I assumed you would go overhead with your dc piping, as I have.

[cody michael]

Does this barn have a foundation, with a sill plate? If so you could use joists to build a platform floor and not have to support it off the uneven concrete. You would have to build it heavy enough to support your machines, but not all that hard. Then you would have plenty of room to go under it with your dc system. I assumed you would go overhead with your dc piping, as I have.

the foundation is rather messed up, I think they pour a slab, then in some spot had 2ft upright pieces of cement (on top of the slab), on some walls the slab has sunk 3-4 inches, I had to shim my lathe and shelving unit so they stand straight.

also money is a major concern, if I can do this for under or around 200$ I may go for it, but much more then that is not realistic for me.

[Nick Coffelt]

Cody,

You appear to be fighting the same dilema I had. My floor was concrete that was cracked and heaved on two ends (8' slabs each end) then with a dirt floor middle. I ended up spanning the entire length with 2/10's. I placed them on 16" centers. I'm an engineer and I designed the spacing to meet the requirements for spacing my plywood as well a a 40 psf Live Load. I used 2/8s as spacers between the joists and set them 1.5" below the top of the 2/10's. This allowed me to install 1.5" styrofoam insulation panels between the joists, my local box store sells them precut for the width. Then I sprayed foam around the edges, used liquid nails on the joists and dropped 3/4" BCX plywood on top. I'd really recommend the plywood over the OSB. It withstands water better and has much better spanning capabilities. In all I went 9' wide by 32' long and ran me about $300. I spread the cost out though.

[Jim Andrew]

You could snap a chalk line on the wall to get the joists even.

[Lee Schierer]

Personally I would not use OSB. Over time it will begin to delaminate and you will get snags and pieces sticking up. OSB doesn't like moisture and tends to come apart back to wood flakes. For a floor like you are talking, I would lay down a 4=5 mil vapor barrier first and then lay down your 2 x 4 stingers. You could use leveling grout or self leveling cement to take care of the low areas. You may need to apply a bonding agent first. Put T&G plywood flooring over that. You can cut foam insulation to fit between your stringers before you lay down the plywood. Use construction adhesive and screws to lay down the floor and you will never have squeaks. Be sure to stagger your joints with the plywood sheeting.

[Gary Yoder]

I don't see any problems with your idea- either level the floor first with concrete,and then lay down a vapor barrier, or first do a barrier and shim 2x4s with wood shims. A carefully laid out piece of 4 mil plastic would be very high on my list of "must do's". If you do go with OSB, use Advantech- much much more water resistant and higher quality than any other I've seen, though you also pay for it... Good luck!

[Mike Heidrick]

Your $200 budget defines this upgrade. Give it a shot. Worse comes to worse you remove it and redo something. Your time is your biggest expense if you can in fact do it for $200. Best of luck and keep us posted.

[cody michael]

thanks for all your advice, I will have to try to save enough penny's and see if I can swing it, first there are some roof repairs I need to take care of, but if I can get them done I will be looking into the flooring.

[Bryan Rocker]

I would suggest that if your going to put down OSB and have heavy shop equipment go with the bigger stuff, 1 1/8". I know for sure Menards carries it.