Flooring over a crawl space

[Bryan Rocker]

I am getting ready to pull the trigger on a 22x36 shop over a crawl space. I have not compromised on much of anything, I have go to 2 beams instead of 1, the beam are running the 36' span and are triple 2x12's or similar. I am going with 2x12 joists and rim boards. After I was reviewing the build list with Carter Lumber, I got to thinking, why am I using just 3/4" T&G OSB flooring? I have done some looking and now I am leaning towards 1" or more T&G plywood (plytanium) or 1 1/8" OSB. I have even considered the advantech flooring. My question is this, I already have a 20" planer, a 10" cabinet saw, and other smaller cast iron. I hope to eventually obtain a nice size jointer and a shaper or two. My question is this, is the 1" over kill or do I need to go to 1 1/8" flooring here?

PS I am going with a crawl because it will only be about 6-10 feet from the house and its on a crawl as well......Don't really like concrete because it just doesn't last and the clay here in Ohio heaves a lot!!!!

[phil harold]

Osb flooring is Sub flooring

the thicker you make your sub floor the stiffer your floor will be

consider adding a a finished floor or at least put 1/4 underlayment down on top of sub floor

[Todd Burch]

I have 1 1/8" T&G ply on the 2nd floor on my house - I would never go thinner again.

I'm faced with a similar scenario when I build my shop, but it will be ~32 x 56. I want to use wood floors. My jointer/planer is 1200+ pounds.

[Sam Murdoch]

Depending on your budget - I would not hesitate to use no less than a 3/4" advantech sub floor with a 1/2" or 3/4" layer of foam insulation board topped with a 5/4 T&G wood finish floor. The finish floor could be an advantech type sheet product but I think the solid wood would be much nicer. Also, if you have access to the ground I would lay down a seamless plastic barrier directly on the ground before closing it all in.

If you can only do one layer of flooring I would definitely go thicker (or 2 layers of 3/4" with perpendicular seams) and cover the ground below.

[Bryan Rocker]

Thanks for your input, my crawlspace will be 40" deep and I will definitely be laying plastic down followed by pee gravel to keep it in place and to control moisture and radon. I priced 1" 1/8 T&G OSB @ Menard's for almost $48 a sheet. Carters, whom I will probably be buying the kit through has 3/4" T&G OSB for $15 each. I can run 2 layers for 3/4 for way less than the thinner stuff. I had planned on doing 16" on center since the span for 2x12's will be less than 8'. I have also considered shrinking them down to 12" OC to ensure I can move my 700lb planer any where I want it. or my 500lb rolling tool box, not to mention any other cast iron I may add to my collection in the future.

Todd, if you do some searching out there you will find some good tables that show you the loading needed for many residential things. I estimate that with 2x12's 16"OC, that the floor will be rated around 150 lbs/ft. which exceeds what is required for residential (40 lbs/ft)

I know so many folks say well just build it to code....my reply is that code is the minimum....if you were in school it would be a "C"....I don't want to get it built and go I wish I would have added X.......my other constraint is height....I have to have it no taller than 16' to the peak from the ground. I am very close with the 12" joists which is why I didn't go with the open web trusses, they would have added another 1' to my height.......

[Scott T Smith]

Depending on your budget - I would not hesitate to use no less than a 3/4" advantech sub floor with a 1/2" or 3/4" layer of foam insulation board topped with a 5/4 T&G wood finish floor. The finish floor could be an advantech type sheet product but I think the solid wood would be much nicer. Also, if you have access to the ground I would lay down a seamless plastic barrier directly on the ground before closing it all in.

If you can only do one layer of flooring I would definitely go thicker (or 2 layers of 3/4" with perpendicular seams) and cover the ground below.


This is what I would advise as well. Much nicer shop floor, plus the added value of insulation.

[Justin Jump]

I was in the same boat here, plus, I plan on wanting the option to wheel in ATV's and Motorcycles to work on them if I ever need to work on them for extended periods of time, i.e. total overhaul or something.

I ened up going with the 3/4" AdvancTech, and 12" o.c. for the joists, HOWEVER, be careful if you are thinking about doing this and insulating the cavities......The normal R-30, which is what I used, my shop is above my garage, is meant to go into cavities that are 16" o.c., not real friendly for 12" o.c., kind of starts to bunch up, now, if you go with spray foam, you better coverage, but defintely more expensive, my quotes were $1500 more than fiberglass.

[Mike Sorge]

Bryan, your timing may be excellent as I have 28 sheets (4'x8') of 1 1/8" Advantech tongue and groove flooring; it's the best flooring for any purpose especially for wood shops with heavy equipment. I was fortunate to find it on sale at $15 p/sheet (1/2 off list price). My wife and I have property out in the country, was going to use the Advantech on the new build once we sold our Westerville (OH) home, but the housing market took a dive and we've changed our plans. If you haven't purchased flooring for your shop yet, you're welcome to it. Also, you can check out my woodturning web site at www.mikesorge.com. Best, mike


Thanks for your input, my crawlspace will be 40" deep and I will definitely be laying plastic down followed by pee gravel to keep it in place and to control moisture and radon. I priced 1" 1/8 T&G OSB @ Menard's for almost $48 a sheet. Carters, whom I will probably be buying the kit through has 3/4" T&G OSB for $15 each. I can run 2 layers for 3/4 for way less than the thinner stuff. I had planned on doing 16" on center since the span for 2x12's will be less than 8'. I have also considered shrinking them down to 12" OC to ensure I can move my 700lb planer any where I want it. or my 500lb rolling tool box, not to mention any other cast iron I may add to my collection in the future.

Todd, if you do some searching out there you will find some good tables that show you the loading needed for many residential things. I estimate that with 2x12's 16"OC, that the floor will be rated around 150 lbs/ft. which exceeds what is required for residential (40 lbs/ft)

I know so many folks say well just build it to code....my reply is that code is the minimum....if you were in school it would be a "C"....I don't want to get it built and go I wish I would have added X.......my other constraint is height....I have to have it no taller than 16' to the peak from the ground. I am very close with the 12" joists which is why I didn't go with the open web trusses, they would have added another 1' to my height.......

[Mike Sorge]

Bryan, your timing may be excellent as I have 28 sheets (4'x8') of 1 1/8" Advantech tongue and groove flooring; it's the best flooring for any purpose especially for wood shops with heavy equipment. I was fortunate to find it on sale at $15 p/sheet (1/2 off list price). My wife and I have property out in the country, was going to use the Advantech on the new build once we sold our Westerville (OH) home, but the housing market took a dive and we've changed our plans. If you haven't purchased flooring for your shop yet, you're welcome to it. Also, you can check out my woodturning web site atwww.mikesorge.com (http://www.mikesorge.com/). Best, mike

[Jim Becker]

I would not use OSB as the wear layer for a floor. It's an underlayment product and will flake off. Personally, I'd put down a subfloor and then use "liquidator" wood strip flooring for the shop floor--un-finished or oiled. Or just a second layer of plywood if the strip flooring isn't practical.

[Bryan Rocker]

Mike that sounds great, I shot you a PM with my phone #.....Look forward to talking to you.


Jim, I assume you mean lumber liqudators cheap flooring for down around $1 a foot. I am ok with that but I am not sure I want SYP as my flooring....maybe oak.......If I am off base please let me know..

PS, my wife bought me one of those EarlX 5000 tonight.....Man I need to get this shop going......will move forward while on vacation this week.

[Jack Wilson50]

Bryan:

I would go with 12" centers, it make a btg difference in the feel of the floor. I am sure your calculations are correct; but you will notice the difference. Just my 2 cents worth.

Good luck with the build. Building a structure or having one built can be both fun and frustrating.

[John Lifer]

I would not use OSB as the wear layer for a floor. It's an underlayment product and will flake off. Personally, I'd put down a subfloor and then use "liquidator" wood strip flooring for the shop floor--un-finished or oiled. Or just a second layer of plywood if the strip flooring isn't practical.
Times 2 on Jim's comment. OSB is fine for subfloor, but you DON"T want it for your final upper layer.

[Jim Andrew]

Something else, try driving a nail in whatever subfloor you are considering using. OSB doesn't have a lot of holding power when you nail into it. If you lay a wood floor over it, be nice if the nails held the flooring down.

[Phil Maddox]

It sounds like you are willing to spend a little more to get it right. If I were in your position, I would use 3/4" plywood, not OSB and nail white oak hardwood over it. A bit of oil/poly or whatever and call it a day. You have plenty of strength with the framing you are using. I have nothing against OSB I just don't think it holds nails as well as plywood. Sumber liquidators has utility grade Oak near $1/SF - thats only $32 for the same area as plywood.

Good luck.

[Sam Murdoch]

I don't know if you guys are lumping Advantech into the OSB category but there really is a world of difference. Advantech is a an excellent subfloor and I think equal to plywood as a shop floor. Both will start to come apart eventually (20 years?) of rolling heavy equipment all around, but for a one person shop they will stand up for a life time. Now having said all that - a wood floor on top of either substrate is my choice if one can afford the extra expense.

[Jim Neeley]

If your plan is to place a 1,200# planer on a wooden floor, I suggest checking the planer base to see if/how the load is distributed at floor level to see if you should place a piece of steel plate under it to distribute the load. If the load transfers to 4 "small feet" at the bottom, your PSI loading may be very high. I'm not talking general floor failure here but could cause problems under the feet. Meh..

[Bryan Rocker]

Had a great visit at Mike's place today while we picked up the Advantech....boy is it heavy.....Mike's basement workshop is the bomb......and he makes some amazing and beautiful things. Thanks for the flooring Mike, my hats off to you and your man cave ;)

[Alan Schaffter]

As I posted in another thread, my shop floor is Advantech subflooring. That stuff is strong, rigid, dense, etc., etc. etc.- much better than OSB. It is the only shop flooring I have and it supports a Unisaw, 20" older style, heavy (1400#) planer, dual drum sander, etc. etc. with little or no flex. The shop measures 25' X 38' and is above my 3 car garage. There are two 25' X 16"(?) microlam beams between each garage bay and no columns. 2 X 12" X 12' joists @ 16" run between the microlams and between the microlams and end walls. The floor is holding up well with little to no flex. The only negative is I painted it with enamel porch/deck paint which is holding up well, but is too slippery. I will eventually lay hardwood from LL over the Advantech.

[Bryan Rocker]

Have any of you guys used plain on 2x4's for flooring? I am asking this because there is a listing on Craigslist for almost 800 4'ers. That's enough to do my entire shop floor. I am asuming I would need to pick a thickness and run them all through the planer to make sure they were all the same.......

On a side note I am definitely looking into an additional layer of either plywood/oak/pine as my top layer. As to the point loads for plywood/osb, once you get down to 12"OC, the PSF they floor will hold is very high, I think 1" is around 5K psf.......