Normally for plank subfloor one is supposed to add 1/2 inch of plywood plus cement backer board for underlayment. For a small area say 4 feet by four feet is all of this necessary?

  • It really depends on what is already there but there should be at minimum a another layer over the planks. I have seen jobs where mastic was used to glue tile directly to the sub floor that held up fine. I have also removed tile that crumbled because the floor flexed. It all really depends on the base and how sturdy it is. Just a note backer board makes the tile much stronger if something is dropped on it it is less likely to bullseye. – Ed Beal Aug 14 '17 at 21:21
  • @ Ed Beal can i use 1/4 inch plywood? plus 1/2 inch cement backer board? – joe Aug 14 '17 at 22:05
  • If the plywood feels firm once down the backer board will add and give a nice base. On jobs I want to be solid I trowel some thinset On top of the subflooring and screw the backer down before it sets this is a little more work but it increases the strength. – Ed Beal Aug 14 '17 at 23:54

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