Opinions on subfloor?

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Old 02-02-16, 10:53 AM
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Question Opinions on subfloor?

Wondering about the best sub-floor material to use in my situation.
Details are I am laying new 12”x12” tile in my kitchen and hallway in a 1960 era house.

The floor before I started had five layers, first diagonally laid ¾” shiplap, ¼” fir plywood, vinyl tile, ½” plywood and finally ceramic subway type tiles.

I removed the subway tiles and the ½” plywood, the floor was quite rigid before I did this but now seems to have a bit of bounce and squeak. I was going to lay ½” cement board and then tile but am now wondering if I would be better off using plywood in the hopes of regaining the rigidity. Or should I just add a ton of screws to the floor now and then lay the cement board?

I have read that you shouldn’t tile over plywood but I’m not sure why, my original tile was done on plywood and I was literally tearing out chunks of the plywood when I was removing the tile so adhesion doesn’t seem to be the problem??
Appreciate any thoughts
 
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Old 02-02-16, 11:02 AM
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Let's start even more basic - what's the size, spacing and unsupported span of the floor joists?

You can rip up the 1/4" plywood and everything above it to start, tile should not be installed over vinyl or 1/4" underlayment.
 
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Old 02-02-16, 11:11 AM
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am not a tile pro - but here is my opinion.

If you are using a thinset mortar the plywood might absorb some of the moisture from the thinset and reduce the adhesion. At least that's what I have been told. I also believe that some modern thinsets have additives to prevent this and they can be used directly on plywood although that is not the ideal substrate.


IMO the 1/4" plywood has to go. It's used to provide a smooth surface for vinyl but can cause problems with tile. If your finish floor height isn't a problem I would strip it down to the plank and lay 3/4" plywood on top. Above that a 1/4" cement board will provide an ideal surface for tile adhesion.

If you are using a premix tile adhesive you can do away with the cement board. That's assuming the plywood substrate is smooth. If the plywood seams aren't perfect it could cause problems.

Did your floor move/squeak with the old tile? If not, your joists are probably OK. A quick check will tell you if the span/spacing is OK for tile. There are span tables on the internet.

You can lay tile over vinyl but I would be 100% positive that the vinyl has a perfect bond. I have never done that before. You can Google a dozen sites that provide info including the TCNA site. As I said, if it were me I would rip it up down to the T&G subfloor (which could well be where your squeaks are coming from.
 
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Old 02-02-16, 11:41 AM
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Answer some questions about the joists first, but prepare to take the floor down to the original diagonal planks. It is there that you screw off and remove offensive noisy nails. Tongue and groove 3/4" avantech or equivilent would then be screwed to the planks. On top of that you would trowel thinset and set 1/4" cement board into the thinset and screw that off. The thinset fills any dips and voids and supports to cement board which is not structural but a superior bonding surface for the thinsets and tile. Tape and thinset all seams on the cement board and then tile.

All the other layers of your mix are strictly for different types of flooring and are not compatible with a tile installation. If you ask enough people, you will find someone to tell you it is OK, but it is not. So I have to disagree with some of CW's direction.
 
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Old 02-02-16, 03:08 PM
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Thanks for the replies!

So the joists are 2x8 on 16" centers and span 12' unsupported. Cross braces are installed down the middle of the span.
It doesn't look like tongue and groove 3/4" avantech is available in my area.
 
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Old 02-02-16, 05:10 PM
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2x8's at 12' are at the extreme limits of the span tables. So, we need to beef where ever we can.

What part of Canada are you from. Do you have Home Depot or Lowes in the area. Check with lumber yards for the correct subflooring. Add blocking where you can to tie the joists in with the adjacent ones. T&G is a must and let us know what you DO have available at your disposal.
 
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Old 02-04-16, 06:36 AM
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I am going to be using plywood and then topping it off with a product called Schluter®-DITRA
matting. Seems to be the thing to use, expensive, but better than cracking tiles.
Thanks for the help!
 

Last edited by Buzz; 02-04-16 at 06:54 AM.
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