I have a question about a hardi backer sub floor. I installed tile 8 years ago and my wife decided she wanted a diferent tile. The sub floor was laid over linoleum with a 1/4 in backer board that was installed with the house build. So feasibly I have 1/2 inch down to the original floor. I tore up the existing tile and it pulled a top layer of the hardi backer off in abouyt 40 % of the area in a small bathroom. It's kind of knarled and pieces of the top layer are loose but not severely damaged to cause the backer to come from the floor. I have screws every 8 inches so it is secured pretty well. I have gotten advice to skim it with mortar and level it all out and then lay the tile. I'm a little nervous about this, I don't want to do it twice. Also, I saw Schuleter ditra product, can I just lay that down and then commence with tiling. I think I can remove the screws and pull the whole thing with a little work but don't want to, Ha. Any advice ?

2 Answers 2


If the damage is not significant (you mention the approximate area affected but not how deep the damage is) you could just tile right over it.

If the missing layer(s) of backer-board are significant enough so as to cause the tile to not lay level and flat, you will need to do something:

  • best option would be to remove and replace the damaged backer-board
  • the Ditra product works well but also requires a flat level surface below, so again it would depend on the nature and extent of the damage.
  • I have had decent luck troweling a smooth skim coat over rough surfaces and letting it cure prior to tile application, and would probably choose this method because it is the simplest/easiest, but this is a skill. Well mixed mortar with the right consistency along with careful trowel work are needed.

I would replace the missing Hardi board. Linoleum does not provide adhesion for the mortar. Screw it to the subfloor with 1/4" thinset below and tape the joints with fiberglass mesh. It will never move

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