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sleeping on a slab

therealpeter | Posted in General Discussion on December 3, 2008 03:56am

In a work/storage area later to be finished as a guest room…
*I plan to put plastic on my slab, then 1″of blue board (I know 2 would be better) with sleepers, then 1″ tongue and groove plywood.
*What is the minimum width for the sleepers (less width=less thermal bridging)
*Do the sleepers need to be attached to the floor or can the insulation and sleepers float?
*Can I get away with 2′ wide foam, meaning over 24″ centers for the sleepers?

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  1. User avater
    Matt | Dec 03, 2008 04:17am | #1

    don'know.  One Q though... Is 1" T&G plywood readily available in your area?  Just curious...

  2. FastEddie | Dec 03, 2008 04:35am | #2

    The sleepers are really only there to level the plywood and to provide something to tie the adjacent sheets of ply together.  If the floor is as flat as you want, lay down a solid layer of foam, then two layers of ply with staggered joints.  You might want to lay a perimeter of sleepers to fasten the outside edges of the ply sammich.

    "Put your creed in your deed."   Emerson

    "When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it."  T. Roosevelt

    1. therealpeter | Dec 03, 2008 04:46am | #3

      thanks QuickEd,
      The doubled ply sounds good; eliminates the concern about the foam degrading from flex.
      As to the 1" I admit to generalizing. If I go with two layers what is the thinnest sheet I can get away with? Also, with two layers of plywood is the T&G needed?

      1. MikeHennessy | Dec 03, 2008 04:08pm | #6

        I'm with FastEddie. You could also eliminate the plastic sheeting with no sleepers. I'd use minimum of 5/8" on the bottom and 1/2" on the top, unless you're planning on tile later -- then I'd go thicker. No need for T&G. I'd fasten the top layer to the bottom with screws (that's why I'd use min. 5/8" on the bottom), every 1' in the field and 6" on the edges.

        Mike HennessyPittsburgh, PA

  3. IdahoDon | Dec 03, 2008 04:51am | #4

    I just finished a floor such as you are describing.

    I cover the floor with grace ice and water then put the sleepers in with the foam as a spacer.  It's much easier to rip the foam on the table saw to what it should be rather than fight an unstandard spacing.

    I put sleepers 12" on center when they are thin, such as what you are describing, because they are too thin to hold the ply by themselves and tapcons are used joining the ply and sleepers to the floor.  The pattern I use is every 12" oc both directions, so it's a lot of screws, but less than that and the sleepers will tend to not stay tight to the ice and water and soft spots will crop up.

    I like the 1/4" hex head tapcons with at least 1-1/4" into the concrete.  A 9/16" spade bit works well to counter sink the heads into the ply.

    On hard concrete the 3/16" screws are much more likely to twist off before seating.  Also, on hard concrete the 1/4" screws go in much easier with a 7/32" drill rather than the 3/16" bit.  If the 3/16" works use it, but if you are twisting off screw heads track down a 7/32".  

    The 1/4" screws with #3 philips and tappered head work well, but my impact driver is very hard on #3 bits.

    As you drill the many holes it will save some agrivation if you vacuum up the dust as each hole is finished or the additional drilling vibration will have a lot of dust falling back into the holes.  I also drill the holes a little extra deep to prevent the screw from bottomingout if some dust does fall back in.

    Since many types of construction adhesive melt foam, getting a foam gun and using an adhesive foam designed for floor/joist use makes life go much easier.

    Even the 1" of foam will make a huge difference!

    If you go with wider spacing on the sleepers or screw them less often you'll most likely have soft spots where the connection to the floor is less than ideal.

    It's a lot of work, but the results are great, and a nail down floor feels real solid over this setup.

    Best of luck.

     

    Beer was created so carpenters wouldn't rule the world.

    1. User avater
      Matt | Dec 03, 2008 02:53pm | #5

      >> I put sleepers 12" on center when they are thin, such as what you are describing, because they are too thin to hold the ply by themselves and tapcons are used joining the ply and sleepers to the floor.  <<

      Not sure I follow you as to why the 12" OC, say, as opposed to 16" OC.  Just trying to learn something....

      1. IdahoDon | Dec 05, 2008 04:47am | #7

        When putting thin sleepers down they are notorious for not being the easiest to keep uniform since concrete is often less than flat and how we are talking about attaching them to the floor is a challenge to keep all the tapcons solid, but not so tight that they strip.  I keep them 12 oc because it's easy to do and results in a more solid feeling floor.  There's nothing wrong per se with other spacings...it's a trade off between insulation/install time and floor feel. 

        Beer was created so carpenters wouldn't rule the world.

    2. Marion | Dec 06, 2008 07:03am | #8

      Can I get by using 5/8" ply over 12" centers? I am doing two floating floors over concrete slabs. Do you screw tapcon through both ply and sleeper? Or screw sleeper and then attach ply?
      Thanks

      1. 31MdlA | Dec 06, 2008 10:37pm | #9

        I'm looking at multiple issues, warming up the floor, leveling it, and sealing out the moisture as there was no barier below the slab. Perhaps I should mention, this is in the house, not a basement.My first thought was a layer of plastic sheeting before the sleepers, foam board insulation, and then ply. But the tapcons will penetrate the sheating - eliminating a complete moisture barrier. Also, there would be no sheeting under the bottom plate, would having it elsewhere, cause the moisture to pond (and rot) the bottom plate? Aren't we inviting mold by trapping the moisture?As to leveling the floor - would appreciate hints. I have 2000sf to do and there is a number of problem areas. John

        1. brownbagg | Dec 07, 2008 12:30am | #10

          why not just stain the concrete and leave it.

          1. User avater
            jonblakemore | Dec 07, 2008 01:31am | #11

            I know that you did the stain on your own house. Perhaps you can answer a question for me.Did you have to do a lot of prep work to stain your floor? I've always been under the impression that, in order to come up with a good finished result, you either have to protect the floor very well throughout construction or you have to do a lot of work with acids and the like.Did you do anything special, or just stain your slab as it was? 

            Jon Blakemore RappahannockINC.com Fredericksburg, VA

          2. brownbagg | Dec 07, 2008 01:49am | #12

            stain as is, the worst looking slabs come out the best looking, honest, gives them charatcer. If you had slab with cracks, it would be awesome compared to a perfect slab.

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