Ceramic tile over unknown subfloor

[ScottKerber]

A friend of mine is doing a kitchen makeover (only refacing cabs). He would like to remove old ceramic tile floor and put down a new ceramic tile floor.

I'm afraid the old sub floor may be plywood (I've only ever laid floor tile over backer board). My house had several layers of lauan as a subfloor for ceramic, which I've since removed.

My concern is not adding height to the floor since they are only refacing cabs and how it will affect appliances. So I'd prefer to help him tile over old subfloor. The existing tile looks like it was done in the 80s and only has a few cracked areas.

Question is, if the subfloor is plywood should I cutout what I can for backerboard or just clean up and tile over? Trying to keep it simple for him. Thanks.

 

[FloorMaven]

Is the existing tile actually on the sub-floor or on underlayment? You can pull an underlayment out and install a backer board or an uncoupling membrane like ditra which adds little height. If your removal destroys the sub-floor then you'll have various other problems. Remember you're going to need a stiff structure to reduce deflection.

 

[Isola96]

Well you can add backer board but a membrane to be honest it will be pointless in this case since its a kitchen.

A backer board might give you a better hold on your thinset and tile other then risking it trying to adhere tile to the old plywood.

the best method would be to replace your existing ply with new either BC sanded or cdx sanded but you will need to prep cdx 1st.

 

[BudCline]

You would think a pro-site such as this would be putting out better information containing industry-approved methods !!!

 

[FloorMaven]

Can you be more specific?

 

[BudCline]

CDX plywood in a tile foundation? Are ya kiddin' me?

Why would a "membrane" be pointless in a kitchen?

 

[Isola96]

CDX plywood in a tile foundation? Are ya kiddin' me?

Why would a "membrane" be pointless in a kitchen?

Because its a kitchen not a walk in shower, membranes are for wetbeds and for that purpose.
If the op wants to add a filler then use a cement board.

CDX?.... Sanded of course has little to no knot holes if there are fill them with thinset skim coat.

 

[BudCline]

CDX?.... Sanded of course has little to no knot holes if there are fill them with thinset skim coat.

Now see...that right there is the problem. Mis-informed!!!
CDX is the junk of the junk, the cheap of the cheap, even tho you may not see the interior knot holes and cut-outs they are there. Knot holes are voids, voids are movement, movement is disaster.

This has been common knowledge throughout the installation industry for decades.

CDX plywood has NEVER been recommended to be used for a ceramic or stone tile underlayment.

Show me in any of the published standards where it says to use CDX plywood as a tile backer. Show me in any of the published standards where it says it is okay to use CDX plywood anywhere in the build-up of a tile installation foundation.

Installing tile atop any plywood can be problematic and risky enough (but it can be done). Using CDX however is out of the question totally.

 

[Ernesto]

Wow, this is an intense discussion.

Just wundering....because I don't go there on wood substrates much but....don't you have to build it up with something besides PB or OSB....then add your CME or Ditra or what ever?

BudCline You would think a pro-site such as this would be putting out better information containing industry-approved methods !!!

Well hmmm, I got no answer for that.

 

[Floorist]

You would think a pro-site such as this would be putting out better information containing industry-approved methods !!!

That's why we count on you.

 

[Isola96]

Lol I completely understand that no one will suggest using cdx and this discussion has been thrown around alot in these forums but I don't care it has yet to fail me.

@ bud show me voids knot holes.

 

[Isola96]

I knew it was going to put me in hot water when I was typing "CDX"

 

[Ernesto]

Now see...that right there is the problem. Mis-informed!!!
CDX is the junk of the junk, the cheap of the cheap, even tho you may not see the interior knot holes and cut-outs they are there. Knot holes are voids, voids are movement, movement is disaster.

This has been common knowledge throughout the installation industry for decades.

CDX plywood has NEVER been recommended to be used for a ceramic or stone tile underlayment.

Show me in any of the published standards where it says to use CDX plywood as a tile backer. Show me in any of the published standards where it says it is okay to use CDX plywood anywhere in the build-up of a tile installation foundation.

Installing tile atop any plywood can be problematic and risky enough (but it can be done). Using CDX however is out of the question totally.

I am just wondering about the "movement". If the hardwood industry approved CDX for wood floors why would that be an issue for tile with an approved CME over it?

What are we talking about, 12" voids or what? I think much of this is over zealous speculation on the part of the ASTM committees.

 

[FloorMaven]

...or an uncoupling membrane like ditra...

I believe ditra is in fact an uncoupling membrane. I didn't reference A waterproof membrane like Kerdi.

 

[Ernesto]

I knew it was going to put me in hot water when I was typing "CDX"

Most of this is free, all you gotta do is register and hope they like you.

http://www.apawood.org/level_c.cfm?content=pub_ply_libmain

 

[Isola96]

I believe ditra is in fact an uncoupling membrane. I didn't reference A waterproof membrane like Kerdi.

Yes
There both waterproof So if you add the Kerdi to the sides you have a shower pan.

 

[Isola96]

Most of this is free, all you gotta do is register and hope they like you.

http://www.apawood.org/level_c.cfm?content=pub_ply_libmain

Thanks Ernesto I guess I should keep to the laminate side of the forum on here lol eek!

 

[Ernesto]

http://www.apawood.org/level_c.cfm?content=pub_searchresults&pK=e178&pT=Yes&pD=Yes&pF=Yes&pubGroup

 

[FloorMaven]

Because its a kitchen not a walk in shower, membranes are for wetbeds and for that purpose. If the op wants to add a filler then use a cement board.

Link if you want to familiarize yourself with an [ame="http://youtu.be/f6FyWs2WZ1k"]uncoupling membrane[/ame].

 

[kd89]

I love shulter. I just still don't see how kerdi is waterproof. And a membrane wouldn't be pointless. There are different membranes... waterproof crack membrane. I wound use ditra mat and go over the existing tile. Skuff up the existing tile and lay the mat over it. Don't forget to use unmodified thinset