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Discuss Floorboard Substrate Preparation in the Tiling Forum area at

  1. DazJWood

    DazJWood Active Member

    I am currently redoing a bathroom. Floor is to be tiled with porcelain tiles.

    The floor is 22mm wooden T & G floorboards. There are a fair amount of boards that have been previously taken up, presumably for access for electrics maintenance/ changes, etc.. Some of these boards have been badly cut for access and also had their tongues removed (I'm sure there's a joke in there somewhere). Some of the boards are also damaged or split. I can make these boards good by either reinforcing them underneath, by way of noggins between joists/ additional supports screwed to adjoining floorboards or replacing them with plywood completely.

    If I repair/ replace as suggested, can I then overboard with 6mm tile backer board (Hardie, marmox, or equivalent) and then tile over? Or should I overboard first with 18mm WBP plywood, then 6mm tilebacker board, then tile, for additional structural strength.

    Another option is to remove all the floorboards and replace with ply but this would be a bigger job as the floorboards span rooms outside the bathroom and the breeze block walls also sit above them. Not only this but 75% of the floorboards are in good condition.

    I would appreciate your thoughts and recommendations.

    Many thanks,

  2. Andy Rhodes

    Andy Rhodes Active Member

    you could replace all the damaged floorboards with new floorboards fix the down with screws the overboard with 12mm plywood then fix backer boards on top of that or the way you've said ,but be wary of the board that run from outside the bathroom as they might be rocking so check them also |& screwed them down if they are rocking
  3. CJ

    CJ Professional Tiler

    If boards are bad, take up, reboard with 22mm ply, then overboard with 6mm Hardibacker or similar. Tile

    If boards are ok.......just Hardi, then Tile
  4. Bond

    Bond Addict

    If the boards are structurally sound, screw ,glue or repair loose boards to joists, when you bed your backer board down the adhesive will lock the boards also.
  5. DazJWood

    DazJWood Active Member

    Thanks for all the advice.

    I've now just finished the pipe work so about to embark on making the floor structurally sound.

    There do seem to be differing views on the need to overboard with ply or not. Any other views are greatly appreciated.


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