Bathroom remodel.

I'd like to consider:

R30 // subfloor // Schluter®-DITRA-HEAT Underlayment // tile


I want to do it structurally correct and not have it squeak or rot, but also want to keep the costs down.

Which is the best for a floor over a cold garage?


Notes: Schluter

  • 2
    It doesn't matter that it's over a cold garage. It's on the warm side of the building envelope. Use whatever suits your flooring plans best. OSB isn't suitable as a bond layer for tile. It's fine below other layers. If any subfloor rots you have other problems.
    – isherwood
    Feb 10, 2021 at 20:57
  • If you are waterproofing the seams with kerdiband there's no problem going over osb. It would be very difficult for water penetration to occur. Just make sure you bond the ditra to the tub skirt or shower curb with kerdifix
    – redlude97
    Feb 10, 2021 at 22:44

1 Answer 1


First that subfloor should be packed with insulation. Second if you are not sure what flooring you are putting down - go with plywood.

If you want to reduce squeaks then glue your plywood down first and then screw it in. Advantech may be better than OSB but glue sticks to plywood the best and plywood conforms to your joists better over time after glued/screwed.

I have put in a lot of flooring and here is what I think when building...

  • if I am building someone a new home I might choose Advantech because ease of installation and maybe it doesn't get ruined before all structure is up...
  • if I am building my home then plywood

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