I understand that 1/2" ply isn't strong enough for a tile floor installation where the joists are 16" on center. But my joists in the bathroom are 12" on center. Does that make a difference? Can I move forward with 1/4" backer and then tile, or do I still need to add a layer of plywood first?


  • Backer board will do the job
    – Ruskes
    Aug 8, 2022 at 23:45
  • Should go by the installation instructions, if they do not mention 12 inch spacing ask the tile makers. Tile(depending on size) does not like any floor movement, so not uncommon to see thickness requirement of an inch plus below the tile(for large sizes).
    – crip659
    Aug 8, 2022 at 23:45

1 Answer 1


Add a layer of plywood. The cost will be minimal and it will guarantee no future problems. Use 3/4" if possible.

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