Anyone consider a "floating plywood slab"

[jumbinidaho]

Planning a 16x48 pole barn/post frame build. It will be partitioned in half, with one half slated as a home gym, and the other will be a shop/gear storage. We will have a door big enough to get a car in on the shop side, but the intention is not to have indoor parking, and I do not particularly like working on cars but will begrudgingly do repairs when necessary and want an indoor space for that since we have long harsh winters.

In researching the pole barn builds, I came across an option i've never heard of - "floating ply slab". It's two layers of 3x4 t&g ply of advantech, cross layed and glued and screwed. If you check out youtube there are a few home builds that utilize it. In terms of construction, for me it would be the exact same process as i'd use for a slab pour, as I plan on insulating sub-slab. I feel like it has a potential number of advantages for my use case:

1. On the gym side I plan on laying padded open cell foam flooring over part of it (about 150 sq ft) Ply would eliminate the need for a moisture barrier inbetween the floor and foam flooring and help with potential moisture issues (right?).
2. Easier to heat - at least thats what i've read in a number of threads here. In case of a slab pour I would put foam around the slab edge for a thermal break, but from what info I could find the ply is a more energy efficient option.
3. Easier on the feet/body. A lot of threads i've read here people seem to strongly prefer wood to concrete floor for shops.
4. I could do it myself and wouldn't need to pour concrete. I'm a carpenter and I really don't enjoy anything about concrete honestly in terms of process. I also have really only poured little landing type slabs myself (and helped on slab and wall pours), so I would probably lean towards hiring someone to make sure I didn't screw up such a large pour.

In my area concrete and ply are both still very high - total cost between the two floors would be similar enough to not bother cost differential between the two (unless I paid someone to help with the slab pour which would make the plywood option cheaper). One concern I have is about the plywood slab on the shop side and driving a car onto it. Again, not planning on doing that often, but wondering if it would be a problem? Another approach , since I plan on partitioning the sides, would be to do 1/2 in plywood, and pour slab on the shop side, but then I would lose the "easier on the body" pro for the shop, which will be predominantly used for projects and not working on the car. Thoughts? Thank you!

 

[billconner]

I have read of it and would consider for a house. It will outlast most people alive today. I think your problem could be overhead door and convincing building department it is in no way a garage. I think non-combustible flooring - code required for parking vehicles - over wood is not an easy find.

The half and half idea makes sense.

 

[jumbinidaho]

I have read of it and would consider for a house. It will outlast most people alive today. I think your problem could be overhead door and convincing building department it is in no way a garage. I think non-combustible flooring - code required for parking vehicles - over wood is not an easy find.

The half and half idea makes sense.

Thanks for the reply. We are continuing to discuss and may just ditch the overhead door and indoor parking options entirely. I really like the idea of the floating ply slab since we'll be primarily wanting to use the space for storage and projects. I was also planning on doing the floor after the pole barn is complete - you can have pole barns out here with dirt floor and overhead doors (so i've been told but need to confirm.)

 

[duneslider]

You can have an overhead door on a house into living space, that doesn't mean you will drive a car into the house but I have seen people put cars in their houses...

Anyway, I would think the floor would hold up to occasional cars just fine. I would be more concerned about putting some sort of layer down in the shop area to protect the plywood when you are in there working on cars. Some sort of durable flooring option would be needed I would think.

I don't think I would want tractors and big rigs on the wood floor but it should be fine for occasional passenger cars and trucks.

 

[jumbinidaho]

You can have an overhead door on a house into living space, that doesn't mean you will drive a car into the house but I have seen people put cars in their houses...

Anyway, I would think the floor would hold up to occasional cars just fine. I would be more concerned about putting some sort of layer down in the shop area to protect the plywood when you are in there working on cars. Some sort of durable flooring option would be needed I would think.

I don't think I would want tractors and big rigs on the wood floor but it should be fine for occasional passenger cars and trucks.

Yah, good points. For how often I actually work on my car I could even lay a tarp down.

 

[kngelv]

16' deep is pretty shallow. You should at least go to 20'.

James

 

[jumbinidaho]

16' deep is pretty shallow. You should at least go to 20'.

James

Unfortunately I am trying to maintain the ability to have a 10' gate so that I can easily drive vehicles and trailers through the property. The building started as a 200 square ft shed, so there's that lol!

 

[Lassen Forge]

We have to do something like that as any ourbuildings MUST be temporary construction, unless you go through the 3 year, maybe you can and maybe you can't semi approval process. I already did something similar using 2x12s on a framework of PT beneath, sitting on gravel, and learned enough lessons there that I feel comfortable doing it here. Being wood, they consider it "temporary construction" so for me its a win win.

I'll probably top it with plywood. Amd if they *****, well, we'll have a bonfire!!

 

[billconner]

I am at least intrigued by ply (or OSB per the linked article) "slab". I think with proper base and drainage it would be fine.

You might consider an inexpensive concrete paver on car half. Should be less expensive than a slab.

I have just gravel in my build (last summer) and debating now gravel, pavers, or slab. Slab is by far most expensive. HD has some pavers around $1.25/sf. Even with sand, etc, a lot less than slab at $12 or more /sf. Pretty pleased with how compacted gravel has stayed in place over fall and winter. Sure solves ponding problems.

 

[jumbinidaho]

I am at least intrigued by ply (or OSB per the linked article) "slab". I think with proper base and drainage it would be fine.

You might consider an inexpensive concrete paver on car half. Should be less expensive than a slab.

I have just gravel in my build (last summer) and debating now gravel, pavers, or slab. Slab is by far most expensive. HD has some pavers around $1.25/sf. Even with sand, etc, a lot less than slab at $12 or more /sf. Pretty pleased with how compacted gravel has stayed in place over fall and winter. Sure solves ponding problems.

$12/sq ft! Jeez! I was told we're at $175cu yd here and i'd need 10 for just the slab, so $1750 for a 785 sq ft slab at 4". I was thinking of doing all the prep myself, so it's really not that bad, but I do really like the idea of a wood floor since they'll both kind of be "hang out" spaces in their own ways and I just am not that big of a fan of concrete.

 

[billconner]

$12/sf bought, placed, and finished. I might find it for less. I wouldn't think about doing it myself.

 

[WisJim]

I know a couple houses with that kind of flooring system and I would seriously consider if I built a new house. We did something similar in a sunroof a few years ago, using used white foam board from a commercial building retooling project and 2 layers of t&g waferboard and we really liked it.

 

[barndobuilder]

Was looking to open a new thread but I think my question might have a good chance to get a answer here.I am about to start the build of a barndo in Texas. I have plans approved from the city but the foundation/slab is needing a lot of hands and it is pretty much just me and my wife.So I am trying to work with my foundation engineer to change it to the point where there is no slab(concrete),you can think of like a horse arena or some building with no concrete slab and instead just have some packed rock and some 4 inch XPS boards with floating 3/4 osb in 2 layers over which I would install some laminate vynil flooring .And now the question: do you think I can drive a car(tesla)over that ?No work on the car would be performed as I will build another building for garage.This is a open concept barndo where the living and kitchen areas are open and so you can drive in your electric car and sort of park it in the living area to charge it.i have never dealt with xps and have no idea if it is strong enough. What I don't want is over time the floor to sink due to the weight of the car.And yes there would be all the proper steps under the xps so there is no water from the rain or other things getting into the sub floor .Thank you all for you input.

 

[billconner]

XPS is plenty strong. At 15 psi, that's over 2000 psf, and double OSB will spread that out more. And 25 psi is available - 3600 psf.