Ceramic tile installed directly to plywood

[James Norman]

This is my first post so go lightly on me.
I was recently in a house and the bathroom had been just been remodeled. The tile flooring was installed directly to the plywood. I have always heard you have to have the backer board because of the different expansion/contraction rates of wood vs. cement. Before I list this costly repair I would like some thing concrete to back my findings.(pun intended)

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[Scott Patterson]

This is my first post so go lightly on me.
I was recently in a house and the bathroom had been just been remodeled. The tile flooring was installed directly to the plywood. I have always heard you have to have the backer board because of the different expansion/contraction rates of wood vs. cement. Before I list this costly repair I would like some thing concrete to back my findings.(pun intended)

Ceramic tile can be installed on a wood subfloor, but it requires specific steps and products to work. The TCNA Handbook (Tile Council of North America) list several ways to install tile on a wooden substrate.

If you do not know how it was installed then all you can do is to inform your client that if it was not installed properly, problems could arise over time. But then this is true with just about everything we are inspecting in a home.

[Ted Menelly]

This is my first post so go lightly on me.
I was recently in a house and the bathroom had been just been remodeled. The tile flooring was installed directly to the plywood. I have always heard you have to have the backer board because of the different expansion/contraction rates of wood vs. cement. Before I list this costly repair I would like some thing concrete to back my findings.(pun intended)

I applied a 12 inch tile to a 36x16 addition directly, well kind of, the plywood.

I used a base of a roll on latex type material. I cannot remember the name at the moment. It is, was, a great product. It was my own home. I never got any separation or moisture problems at all and no cracking or lifting. I just talked to the man recently and the floor is doing great with no problems at all, 10 years later. This is over a crawl in Neptune Beach Florida 3 blocks from the ocean. Lots of humidity but plenty of ventilation. Also sandy soil so the home moves around about zip.

There are ways to apply tile to almost anything. There are tremendous products out there. If it were me, as in the kitchen and baths of that home, I would have installed a backer board (wonderboard, hardi board duroc etc) in those wet areas. That's just me.

[home london]

I think you need a water proof plywood and use flexible adhesive

[home london]

something like this, sorry I can't find a better picture

[Jeff Zehnder]

You will need to provide more information… As previous posts have stated it is possible to successfully install over plywood but the issue is in the details.

How think is the subfloor? How far apart are the floor joists? What is the span? What type of plywood was used?
Can you determine what type of mortar or glue was used.

If you are in doubt just include the details that you can observe in your report without making judgment and if you are still concerned recommend further evaluation by a tile specialist

[James Duffin]

The biggest thing is that the tile sub-floor can not flex at all or the tile will crack.

[Markus Keller]

Too many possibilities from what you've posted.
6x6 or smaller should be OK but it will depend on the things Jeff noted.
8x8 or larger probably won't last.
Plywood is Ok with mastic. However, how was it applied, was the plywood dry, was it glued and screwed or just nailed, etc.
There are lots of products out there that claim you can apply them to plywood and allow thinset and large tiles to be Ok. As a contractor, I would not do it nor recommend it. I've seen far too many failures on other people's jobs. It's helpful to remember that we use plywood forms to pour concrete foundations. After the concrete dries, the plywood pulls right off.
I did an inspection a few months back on a house. Nice new 12x12 tile floor. Tiles were started to come loose, grout was popping out of joints. I pulled the floor register to find thinset on top of plywood. Seller stated the floor was only a 2-3 months old.
Tap the tiles to hear sound variances and look at grout joints closely.
Hope that helps.