# 12x12 ceramic over plywood subfloor



## GO Remodeling (Apr 5, 2005)

I know what TCNA requires with ply but how is a Ditra installed over one layer of plywood that much better in strength than two layers with 5 ply? Seems the 5 ply would be better even if it isn't the required 7 ply. Just saying. Did Dave Gobis explain?


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## Bill_Vincent (Apr 6, 2005)

Not sure. Like I said, I'd never even seen 7 ply 3/8 multi-ply, so I wasn't worried about it. I just stay away from Multi-ply now as a rule.


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## JohnFRWhipple (Oct 20, 2009)

I got setters up here in Vancouver that love setting over plywood but I don't think they follow Bills advice.

I like Bill's comment about seeing the latex go in and the other about the Weldbond. Same theory and this binding agent is not in a dehydrated form.

The hard part I'm having trouble with Bill is the no glue between sheets of plywood. I have always done this. Glued and Screwed and never a call back. Have I just been lucky?

We glue a screw one sheet at a time and use a wack of screws. Top layer not into the joist and like you use Dap Chaulking over the seams. I have never tiled over plywood and we on most jobs are going into floor heat and then Ditra or something Equivalent like Durval or Spider Web.

What is the reason to skip the glue between sheets of plywood?

JW


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## Bill_Vincent (Apr 6, 2005)

I've also heard this brought up to Gobis, and his response was I hear that every day..... in court--" I've done it this way for years with no problems"

The problem is that once again, it creates a larger single layer, and completely negates the benefits of double layering the floor. You might as well be going over a single layer of 1 1/8" sturdi-flor (which is also NOT acceptable)


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## JohnFRWhipple (Oct 20, 2009)

All right Bill.

You've schooled me.

I'll skip the glue going forward.

Thank you sir.

JW


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