Wooden floor thickness for shop

[Dean Coss]

I’m building a 30’ x 40’ shop that is essentially going to be built on a deck frame type structure due to the shop is partially located atop an incline. I priced it out and between building it that way versus putting up a retaining wall and concrete, the deck frame is a third the price. So, my question is, what kind of thickness of flooring will I need for my shop? I’m thinking 3/4” pressure treated plywood on top of the frame, which would be pressure treated 2x8 joists, 16” on center with 2x8 spacers between the joists as needed. I have the typical machine equipment: 6” jointer, 14” bandsaw w/ riser kit, contractor table saw, floor drill press, 13” planer, etc. The point is, I don’t have anything insanely heavy that myself and a buddy can’t lift. Is 3/4” plywood enough for a floor? Do I need more? Any thoughts on this from people with experience in building a wooden floored shop would be much appreciated. Thank you.

[Jim Andrew]

I put 1x2" sleepers over my concrete floor at 16"oc, and 3/4" t&g flooring over those. Have a 12" jointer, a unisaw, 15" planer etc.

[Wayne Lomman]

3/4 ply and 16" joist spacing will do a good floor provided your joists and bearers are correctly calculated for span. You need to find out what stress grades of timber you are using and calculate from that. The Engineered Plywood Association is a good source of info. Joist and bearer span tables are easily found on the net as well. Cheers

[Jim Becker]

3/4" will likely work, but a double layer or 1" would be stiffer. 3/4" plywood covered with a "more finished" floor, such as surplus hardwood strip flooring would be "really wonderful" if the budget allowed.

[Bill Dufour]

Sounds like a house foundation and floor. Just look up what a house floor requires and maybe bump it up one thickness. I am not sure but I think code requires any crawl space to be at least 16" above ground contact. So why waste money on treated joists? If it is that damp the plywood is going to rot anyway.
Bill D

[Steve Milito]

I used 1-1/8" advantech subfloor on 16" centers. It's way overkill but I'm fairly certain I could put any machine that I could power without any issues. 3/4" plywood should be fine, I'd be more concerned with the span of the 2x8s.

[Larry Foster]

I just did a floor in my soon to be new shop.
I was on dirt so I only used 2X4 16"OC with 3/4 plywood.

It's solid but a little springy in spots

[Don Jarvie]

Don't use PT ply. Go with OSB or Reg ply. The moisture in the PT will dissipate in the shop. Dont forget plastic under the ply to keep the moisture from coming from below.

[Bill Adamsen]

Depends on the sub-floor framing and your loading requirements, need for dent resistance, and aesthetic needs. My shop floor is 2-3/4 T&G Hemlock. Were I to do it again, I would lay down 1x T&G pine (for the below ceiling) then 1-1/8" T&G plywood atop that, then some very hard (Janke test) T&G hardwood probably 3/4 or 5/8th. My floor joists are separated about 22" but they're 8x8 red oak. The floor loading is 150# per square foot.

[Eric Van Cronk]

The best bang for your buck would be 1-1/8” T&G plywood subfloor.

Since you you said that you’re using 16 OC 2x8s I would assume the span is no more than 8’.

Good luck w/ your build.

[roger wiegand]

My shop has a concrete slab with 2x 4 sleepers on the flat, 3/4" plywood subfloor, and "mixed domestic hardwood" flooring on top of that. It's very comfortable to work on, withstands rolling big machines around without any problems, and looks pretty good too!

I would have loved to have been able to run dust collection under the floor, but didn't have the headroom. I am able to pull wires in the spaces between the sleepers for power in the middle of the floor.

[Mike Cutler]

Dean

I'd personally drop the pressure treated ply for use in any occupied, enclosed, living space. There's still some nasty stuff in pressure treated products.
One 3/4" floor layer will not be enough.

[Rollie Kelly]

Don't forget insulation, cold feet are a misery.

[Steve Milito]

FWIW and somewhat off topic:
When I had my shop designed I wanted a wooden floor and originally a basement but the basement proved over budget so I went with a crawl space, The builder highly recommended slab because of cost and weight concerns but as he said, it was my money. He did insist that we have it engineered. So basically, the engineer wanted to know the footprint and weight of what I intended to put in the shop so I went big. Here's the gist of how he approached it.
The footers, posts, and beams determine the total load the structure will support. Basically, that system ended up being a grid of concrete posts, in a grid of footers, to support, in my case, oversized beams. The joist span determines the floors deflection in the that direction. I believe we went with a load of 150 lbs/ sq foot for the deflection spec he wanted, but it's been a few years. The subfloor / floor design determines the inter-joist deflection. Thicker subfloor allows wider joint spacing for the same deflection or less deflection for the same load. We went though all the options, 3/4" + 1/2", two layers of 3/4", but opted for the 1 1/8" advantech to save labor cost. That stuff is amazing and would allow 48" centers for residential code. I topped it off with utility grade oak and couldn't be happier. It's stiff and will literally support a ton. I'm sure I could drive a car on it!
Bottom line, the flooring is 'system'. The details are probably not important for your average residential shop but could be for people looking to use surplus commercial equipment.

[Richard Wolf]

I have the same situation. 30 X 34 shop on a framed floor. 2 x 8 on piers, 3/4 pressure treated ply on the floor is not enough, I am topping it with 3/4 particle board flooring. The 3/4 ply by itself is not boncey, but you can tell when you are standing between joist.