Floor prep for Tile on old wood floor *Help before I mess it up!* :)

Discussion in 'Floor Preparation' started by Petrinad1, Nov 22, 2017.

  1. Petrinad1

    Petrinad1 New Member

    I am renovating an old cottage built in 1925 and am installing a new bathroom on the first floor. However, the original flooring is about 2 1/2 inch thick old wood that is very rough cut and kind of lumpy and uneven with some small holes (1") from old pipes etc.? There are some spots a little worse than the picture I have but this is the general idea.

    My question is would this be an adequate sub-floor to screw the concrete board to before tiling or should it be a smoother more even surface so the board wouldn't crack from any small air pockets?
    Some suggestion have been...
    - Primer & self leveling before the concrete board? (but I'm afraid the self leveling will crack?)
    - 1/2 plywood and then concrete board

    My other concern would be raising the height of this floor too much higher than the hallway floor. I currently have about an 1/2 inch between the existing and hallway hardwood.

    ANY Professional advice would be greatly appreciated. This is all new to me and I would hate to approach this wrong and have many worse and expensive problems in the future!!

    Thank you so much for your time.

    Attached Files:

  2. Mark Brown

    Mark Brown On The Surface Flooring I Support TFP

    Oh the good old days. Site cut timber floor boards are wonderful. Not so fabulous for us here in the 21st century.

    First step I would take is to screw every board back into the joists. 2 screws in every board at every joist. Did this a lot for old ship lap and it sucks for sure :)

    Sand down the existing floor so it isn't so lumpy and bumpy then sheet it. If you can manage the additional plywood that would be ideal. If the structure is as solid as I would imagine it to be, you might get away with just cement board. Joists are 16 centres?

    Would never recommend self leveler on that... nope
    • Agree Agree x 1
  3. Kman

    Kman Tile Expert I Support TFP Senior Member Published

    Cement can only be installed over plywood or OSB. You would have to have a minimum of 1/2" plywood screwed to the subfloor.

    Before that, the floor needs to be flat, and you should check the joist system underneath to make sure it will support ceramic tile, which has to be L/360 or better. There's a span calculator here.
    • Agree Agree x 1
  4. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    I would use exterior grade plywood after sanded, screwed the hell out of, then use a crack suppression membrane, and forego the cement board.
  5. Mark Brown

    Mark Brown On The Surface Flooring I Support TFP

    I personally have never understood cement board, or used it. I do not have the knowledge in my wee little head to tell my why it is good.
  6. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    Op may not realize cement board is set over thinset to fill voids underneath.

    It was used to get better bond, kinda the mud bed technology mindset.

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