What wood for shop floor ?

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Forum topic by pdxrealtor posted 05-26-2015 07:16 PM 1060 views 0 times favorited 16 replies Add to Favorites Watch
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104 posts in 1191 days

05-26-2015 07:16 PM

I’m building a shop, outside on piers so the bottom of the floor will be exposed to outside.

I’m looking for a 3/4” product.

Can you guys provide some suggestions?

Tongue and groove preferred-
Advantech OSB (

or ??

Any treating I should do to the underside for longevity?


16 replies so far

View Bluepine38's profile


3379 posts in 3052 days

#1 posted 05-26-2015 11:37 PM

Tlhe Advantech flooring is a product I have heard good things about, have not actually used it, but they do
have a wonderful web site with all sorts of information on installation which should answer your question
about any coating to be used on it.

-- As ever, Gus-the 79 yr young apprentice carpenter

View pdxrealtor's profile


104 posts in 1191 days

#2 posted 05-27-2015 12:01 AM

Thanks. I just caught this on their website -

It seems using this product as a floor only (not top layer) would result in 1) gaps in my floor or 2) buckling and uneven layout on a 16×24 floor. The sheets are just less than a full 4’x8’.

View TravisH's profile


573 posts in 1902 days

#3 posted 05-27-2015 02:22 AM

I used ply with 2×6 joists on hangers when I redid the floor in my shop 14 years ago. I have pulled sections of the floor up in two different areas (one last year and one this past weekend) while correcting issues related to the ding bats that built the shop. The ply underside honestly looks brand new. I am sure treating it would increase the life span but after 14 years no issues so far. The floor is about 9 inches above substrate and my shop sits on a wood foundation (no idea why one would go this route besides cost) so gets no air flow.

View TheWoodenOyster's profile


1313 posts in 1902 days

#4 posted 05-27-2015 12:43 PM

I have searched CL with some success finding sheet goods like T&G plywood and osb. I think those will be your cheapest solution and involve the least amount of headache. Of course you could use 4/4 oak or maple or something if you really feel nostalgic, but I think ply and/or osb would work just as well. I’ve been planning a shop too and have been thinking about the same question. If you roll heavy machines on top, 3/4 osb might not like it much, but I bet 3/4 ply would be fine. You could always do two layers of osb if you felt it wasn’t strong enough.

As far as treating the underside, I would maybe put a vapor barrier or rigid insulation below the ply to slow the absorption of moisture from the raw earth below. It probably isn’t that big of a deal though. Lots depends on your climate.

Good luck

-- The Wood Is Your Oyster

View Hermit's profile


186 posts in 1292 days

#5 posted 05-27-2015 03:26 PM

I would use pressure treated plywood available almost everywhere. A little pricey though at about $35-$40 a sheet. Can also be found in tongue and groove but is 1-1/8” thick and even more pricey.

-- I'm like the farmer's duck. If it don't rain, I'll walk.

View Richard H's profile

Richard H

489 posts in 1648 days

#6 posted 05-27-2015 04:03 PM

In my dream shop I would build the floor joists 12” on center and cover with plywood than a solid hardwood flooring like oak so someday it could be refinished easily. I have worked in a shop with hardwood floors and they add a lot of warmth and comfort to the space. I know that’s also a very expensive option which is why I call it a dream workshop option.

Practically I would think anything that could stand up to the traffic of the machines would be a good option. I don’t like exposed pressure treated lumber myself as it irritates my skin and I hate the look of it but that’s me. OSB and plywood are left exposed to the ground often in subfloors and as long as they don’t contact the ground I think it’s generally ok but it also might be dependent on where you are. You could always ask your building inspector office? They are usually willing to answer questions and I found them pretty helpful overall.

View dhazelton's profile


2756 posts in 2264 days

#7 posted 05-27-2015 06:39 PM

If you have good airflow and put down a vapor barrier first regular plywood will hold up fine. May be some flex in it though, so two layers (run perpendicular to each other) or another flooring type on top of that would be preferred. If not I’d put the joists 12 inches on center.

View pdxrealtor's profile


104 posts in 1191 days

#8 posted 05-27-2015 07:16 PM

Advantec is not readily available in full face sheets, and I planned a 16×24 floor for ease of building/cost savings from the floor up. I’m not about to buy sheets that are a 1/2” short so I went with a 3/4” t/g plywood.

The height above ground at the lowest point is ~4-5”, and higher over the majority of the floor. Add to that height 11.5” because I’m using 2×12s as my 3 beams. I’ll tie those together with 2×6 joists 16” OC, so I’ll have a pretty solid floor and plenty of air flow.

View splatman's profile


586 posts in 1366 days

#9 posted 05-27-2015 07:58 PM

Lay polyethylene plastic sheeting on the dirt, wall-to-wall, to stop moisture vapors. No need to use PT lumber in the floor. Make sure the crawl space gets good airflow. Add vents if there are none/too few.
Keeping moisture vapor at bay has many benefits: easier to control the humidity, cast iron surfaces do not rust, finishes dry faster, mold won’t grow, etc.

View firefighterontheside's profile


17955 posts in 1824 days

#10 posted 05-27-2015 08:04 PM

I built my shop in a similar fashion. It’s 12×24 and similar distances to the ground. I used all treated 2×10’s for joists and then laid in panels of corrugated plastic on cleats at the bottom and then put in some blocks every four feet to help support the seams of my non t&g plywood. My only wish is that I would have insulated. I didn’t plan on heating and cooling in the beginning.

-- Bill M. "People change, walnut doesn't" by Gene.

View bigblockyeti's profile


5096 posts in 1688 days

#11 posted 05-27-2015 08:29 PM

I would use 3/4” T&G PTS and glue 2” blue styrofoam between the floor joists before laying the floor to act as insulation and a vapor barrier.

View Blackie_'s profile


4883 posts in 2480 days

#12 posted 05-27-2015 10:11 PM

pdxrealtor take a look at my blog on my shop addition, the original building I used 3/4” ply the addition I went with OSB and wish I had used OSB on the first build.

Treated lumber is not needed nor do you need to treat untreated lumber, just be sure your exterior wood and skirting has a nice good coat of paint on it and as some have mentioned be sure to glue in between the tongue and grooves, once after the floor has been laid be sure to put a sealing paint down with a high gloss finish for outdoor porches that comes in the gray color, you can use either tar paper or plastic for the barrier, I didn’t use the barrier on my build as the paint on the floor I think is sufficient but if you want to use it I’d put it between the floor joist and the flooring.

-- Randy - If I'm not on LJ's then I'm making Saw Dust. Please feel free to visit my store location at

View Woodknack's profile


11482 posts in 2347 days

#13 posted 05-28-2015 04:22 AM

My shop is on piers and has a plywood floor, it was built in the early 70’s, floor hasn’t rotted out yet. If you can afford it I would put an oak floor atop your subfloor and you’ll be good forever.

-- Rick M,

View pdxrealtor's profile


104 posts in 1191 days

#14 posted 05-28-2015 05:51 AM

I should name this shop build something like the minimum needed to get the maximum benefit.

I’m not doing insulation in the joists, no vapor barrier either.

I am doing PT for the 2×12 beams, and for the 2×6 floor joists. It might cost a bit more vs. painting bare wood but it’ll be quicker.

It’s high enough off the ground where it will get tons of airflow. If I cover the gap at all it will be with lattice.

I tilled the ground up tonight, and soaked it with grass/weed killer. Got the entire floor being dropped off tomorrow.

I do need to read up on proper T/G installation. Rick M – I’ve read in a lot of different places, and been told by several different people that plywood will do just fine. I figured if I could get Advantec for a similar cost and it was better then why not. But…. it turner out to go against this builds theme of minimum for maximum. haha.

View pdxrealtor's profile


104 posts in 1191 days

#15 posted 05-28-2015 05:54 AM

@Firefighterontheside – how are you heating your shop?

I plan to install a 9k btu mini-split (ht-pump/A/C unit)

Walls and open ceiling will be insulated.

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