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Thread: Ordered insulation for my shop floor, but....

  1. #1
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    Ordered insulation for my shop floor, but....

    My shop is a 12x16 shed. The floor is 3/4" tongue and groove sheets over 2x6 joists at 16" on centers. In the winter the floor gets very very cold even when I leave my heater on 24/7. So today I was at Lowe's and ordered some Dow XPS 1" UtilityFit insulation boards with an R value of 5. I plan to put that on top of my current floor and then another layer of 3/4" tongue and groove over that. Basically the 1" XPS insulation boards will be sandwiched between 3/4" flooring.

    The XPS boards have a compression rating of 15 psi. Is that sufficient for my cabinet table saw, bandsaw, drill press and more importantly, my Robust American Beauty lathe (approx. 800 pounds)?

    The flooring I ordered is 23/32 CAT PS2-10 Tongue and Groove OSB. Was this a good choice for a floor, or is plywood a better choice?

    Any suggestions on what to cover it with? I was thinking outdoor deck paint.

    Delivery is scheduled for Thursday so I have a couple days to make changes if needed.

    Thanks.

  2. #2
    If it were me, I'd use ply instead of OSB for heavy loads, and use 2/3's laid flat and nailed/screwed in place directly over the existing joists that are under the first layer. It would create a small air gap, keep the insulation from compressing and add a bit more strength to the floor. Insulate between those "furring strips".

  3. #3
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    144 in * 15psi =2160lb sq/ft = your fine lol.

    Tyvek tape the seams.
    Glad its my shop I am responsible for - I only have to make me happy.

  4. #4
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    Maybe it's too late for this, but couldn't you just get someone to inject foam into the spaces between the existing joists?

  5. #5
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    Just make sure any point loads are spread out with little pads under the feet. Like a short piece of 2x4. Or some scraps of the flooring plywood.
    Bill D.

  6. #6
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    I would put in sleepers that are 1" thick at 16" OC spacing with the insulation between them to provide adequate support for the new top floor surface. I would not personally use OSB of any kind for an exposed floor surface. This material is not meant to be subjected to constant "touch" and it will splinter. Use T&G plywood or see if you can find some inexpensive strip flooring at places like Lumber Liquidators.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  7. #7
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    I agree with others that are say no to OSB. By putting sleepers directly over top of the joists, you will effectively increase their size, which wouldn't hurt. But if your doing all that work, why not go with 2" insulation? Same amount of work.

  8. #8
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    Quote Originally Posted by Frank Pratt View Post
    I agree with others that are say no to OSB. By putting sleepers directly over top of the joists, you will effectively increase their size, which wouldn't hurt. But if your doing all that work, why not go with 2" insulation? Same amount of work.

    I had thought about 2" insulation but then I would lose almost 3" of headroom. I'm only willing to give up no more than 2".

    My original plan was to use sleepers but from everything I had read I understand that sleepers create a thermal break allowing cold air back through the floor (sleepers have none to minimal insulation properties). I know where the lathe will go and will do sleepers or a pad for the feet instead of insulation under the subfloor. I may still consider sleepers if I can find 1" boards.

    I leave my shop heated 24/7 at about 68 degrees. Last winter the floor was in the 30s on the coldest days, 40s the remainder of the winter. I have Raynauds and neuropathy in my feet so cold floors are very painful. I think that even a little bit of insulation is better than what I have right now.

    Thank you for all your thoughts on the OSB. I'll take a look and see if they have t&g plywood. I saw some inexpensive laminate flooring that I could put over the OSB. Currently I have sheet vinyl on the floor and its held up remarkably well over the past three years so I may just reuse that.

    Spraying under the shed between the joists would have been ideal but there is minimal access (4" height at most). And I would have been concerned with rodents, squirrels and skunks tearing it apart for nesting material.

  9. #9
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    So I did some calculations. My shop is 196 square feet. With the OSB tongue and groove subfloor panels and inexpensive laminate flooring on top it would cost about $320.

    If I go with tongue and groove plywood subfloor which is twice as expensive as the OSB the cost would be $228. Would I need to add something on top of this or could I paint this with a durable deck paint? Valspar solid deck stain is about $40 for one gallon.

    Cost is important but I'm willing to spend a little extra for a floor that would be more durable in the long run.

    If I decide to use some sleepers is there anything commercially available at the big box stores that is 1" thick or will I need to rip some 2x4's down?
    Last edited by Damon McLaughlin; 10-23-2018 at 12:21 PM.

  10. #10
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    If the AB leg pads are 4"X4", your static load is 12.5 psi under the pads, in my estimation. The flooring will allow for some load distribution across the insulation. The dynamic loads associated with turning unbalanced blanks (unless your AB doesn't shake) would be higher. It would be the dynamic loads that would give me pause on using OSB from the leg pads contacting the floor. When you start bouncing 800 pounds on OSB....you get the picture.

    FWIW, my AB has walked off the little rubber pads that came with it while turning out of balanced blanks on occasion. Also, when it shakes the AB's legs will move (change height vertically) as they are only clamped at your height setting, not pinned or screwed.

  11. #11
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    Thank you Eugene. Do you think that I would have the same issues if I used plywood instead of OSB? Where the legs of the AB are placed instead of having the 1" insulation under the plywood if I were to put a wood pad under the plywood what size would you recommend? I was thinking 12" square but I would have to find something that is 1" thick.

  12. #12
    If you glue (construction adhesive) the foam down and then the plywood on top you are essentially creating a torsion box and it will be very stiff including under the lathe. If you found that it still moved a touch you can always bolt a steel plate to the floor under the entire machine and bolt the lathe to it. If that didn't do it then you have to get under the shop and put more support beneath the lathe. I seriously doubt you will ever need go beyond the gluing. Easier to better shape the blanks before mounting so they aren't badly unbalanced.

  13. #13
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    If you go with the plywood, then you wouldn't "need" the laminate. But if you are using the laminate, then the OSB would be fine, IMHO. You just don't want "exposed" OSB for the floor, even painted.

    Yes, sleepers might slightly compromise the insulation quality, but that would be balanced by a stiffer floor. A mid-range solution would be to use some in the areas where you KNOW you'll (permanently) have a heavy machine while floating the rest of the floor just on the insulation.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  14. #14
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    Thank you all for your input and advice.

    I changed my order and replaced the osb with tongue and groove plywood. And instead of going with laminate flooring I decided to get a gallon of oil based polyurethane specifically for floors. Its enough to do two coats with a little left over. I couldn't find 1" thick sleepers for where I know the lathe will be but I'll rip some 2x4s or run some oak boards that I have through the planer. Rain is forecast on and off for the next week and I'll need to move a lot of my equipment outside to get the floor done, hopefully I'll have it done quickly.

    I bought some tubes of adhesive specifically for xps foam board insulation. I am thinking of using it to tack down the foam boards. Should I use it to glue the plywood on top of the foam? I had originally planned on using wood screws to screw through the plywood and foam into the original osb subfloor.

    The nice thing about having such a small shop is that it shouldn't take very long to complete the job.

  15. #15
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    Dennis, your local home center and/or lumber yard should have 1" thick trim material available. (sometimes labeled 5/4 but "finished" to 1", give or take one of those proverbial hairs)
    --

    The most expensive tool is the one you buy "cheaply" and often...

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