Tile underlayment

Old 07-10-10, 11:55 AM
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Tile underlayment

I'm renovating a full bath. I intend to replace vinyl with tile. I pulled up the vinyl and found a 1/2" plywood underlayment ring nailed to the 1/2' subfloor. No problem, I'll just pull up the 1/2" stuff and replace it with 3/4".

Unfortunately, the underlayment is seriously glued to the subfloor. It looks like when the job was done someone actually spread construction adhesive on the playwood. If I can't come up with a few options I'm looking at removing the entire bathroom floor.

I'm thinking about adding 1/4" birch plywood over the existing. I would go with 1/2" but that will give me some transition problems. I also looked at tempered hardboard but I don't think it has any structural value.

My question is, will 1/4" plywood atop the existing 1" provide enough stiffness for tile? The floor joists appear to be true 2X10 on 16" centers. The span is only 8'. I have no idea what species.
Old 07-10-10, 01:51 PM
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I think you will be okay leaving the two layers of 1/2 ply. You will still need a cement board or Ditra membrane over that though, then your tile. Cement board would be 1/4 and the Ditra would be 1/8".

I wouldn't install any plywood less the 1/2", so no 1/4.

Your joists meet the spec for either ceramic or natural stone, so that's good.
Old 07-10-10, 06:42 PM
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What Mark said....................
Old 07-10-10, 07:51 PM
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What Chandler said........

Remember, you don't have an inch of subfloor, you have two 1/2" sheets. It makes a difference and is probably why they glued it. Two half inch I believe is weaker than one 3/4".

I recommend Ditra over 1/4" board. First off it's a better system all around, it's also thinner at 1/8" installed while the board will end up atleast 5/16 installed with the thin set.


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