Hardwood over OSB?

Discussion in 'Remodel Forum & Blog' started by Erico, Jan 27, 2011.

  1. Erico

    Erico Member

    Nov 17, 2007
    Chicago, IL
    My previous post of Hardwood over concrete is kaput since I hauled 1500 pounds of concrete down 3 flights of stairs. It was too compromised to go over with hardwood. Hj was correct - the tiler who set the tile did it the old fashioned/right way.

    Now for the new dilemma.

    I have to make up a differential between the hall/dining floor of 2.5 inches (there was a previous step down to the kitchen which I would like to avoid).

    The floor, as it stands, is fairly level. About an inch differential over 18 feet. I don't think I need to run sleepers and shims to level - I can live with a slight diff. Besides ,sleepers - 2x4s on the flat - would put me too high with 3/4 ply and 3/4 flooring. ANy other ideas for sleepers? I'm thinking anything less than the 1.5 inch would be weak between the shims.

    I'm thinking I might sandwich a layer of 3/8 between 2 layers of 3/4 ply or MAYBE OSB?????? To get me to 2.5 inches with the hardwood (including the 16th they short you on the 3/4 ply).

    I guess I have a couple questions:

    Is hardwood over OSB kosher? I don't need it for strength. It's just being used for shims over the subfloor.

    If not OSB, would CDX be good enough? I know CDX is no good for tile work due to the voids in the ply but will it be acceptable for wood flooring.

    I'm trying to avoid the 33 dollar a sheet for two layers of b/c sanded. A combination of OSB and ply might work.

    Any ideas or suggestions?
  2. Erico

    Erico Member

    Nov 17, 2007
    Chicago, IL
    Narrowing down my question after doing a little googling I think hardwood over OSB directly is not a good idea.

    Now I'm thinking two layers of 3/4 osb with a good layer of b/c plywood.

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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    Not all OSB is created equal. Advantec has a 50-year warranty and claims the same or better nail holding ability as ply. I think I'd try 2x4 sleepers that I trimmed so that the floor would end up at exactly the desired height AND level. If you put down a lattice to hold them upright, you wouldn't need to attach them to the concrete, although you could use some construction adhesive if you wanted. You'd set a level string line at the desired top of the 2x, set a 2x beside it, trace the level line on it (you could snap it if it was a chalk line), then rip along the line. Flip it over, and you'd have a perfectly level shim and the factory edge on top. Put these things at 16" OC, glue and ring-shank nail the subflooring to it, and it would be very solid.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    OSB is NOT dimensionally stable if it were to get wet, so I would not use it as substrate for ANY flooring. One inch in 18 feet is NOT almost level, but might not be too objectionable as long as you do not drop marbles on the floor and have to chase them to the low side of the room.
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