Need Advice on Plywood and Underlayment Choices for 1967 Kitchen Reno with Ceramic Tile Installation

[Maciek]

Hello everyone,

I'm in the process of renovating my kitchen, which is on the first floor of a house built in 1967. After removing the old vinyl tile, I found a layer of 3/4" plywood followed by a paper barrier and then a plank floor with tongue and groove. I've decided to replace the 3/4" plywood but am unsure about the appropriate grade to use for this application. Additionally, I'd appreciate recommendations on a suitable replacement for the paper barrier.

To provide further context, I'll be installing ceramic tiles on top of the new plywood and barrier. What grade of plywood would be best suited for this, and what modern underlayment or barrier should I consider to ensure a stable and long-lasting tile installation?

Thanks in advance for your insights and suggestions!

 

[Snoonyb]

Welcome.
The finished height relative to adjoining floor levels would be my 1st consideration, next the soundness of the T&G subfloor.

If the "paper" is asphalt impregnated, that would lead me to believe that the ply was an interior grade and was a vapor barrier.

 

[Maciek]

Thank you for weighing in Snoonyb.

You're right, the height difference between the renovated kitchen floor and adjoining floors is a critical consideration, especially when adding layers like a backer board. This is something I'll need to measure and account for to ensure a seamless transition between rooms.

Regarding the T&G subfloor, it seems to be in relatively good condition, but there are areas of concern. This is why I initially thought of replacing the plywood layer.

As for the "paper", it does appear to be asphalt-impregnated. If this served as a vapor barrier, what would you recommend as a modern replacement if I decide to remove it? Would a modern underlayment like Ditra be sufficient, or should I consider an additional vapor barrier beneath the plywood or backer board?

Your insights are appreciated!

 

[Snoonyb]

Thanks. The material in photo #2 appears to be standard dia. sheeting, so the simplest solution will be either the Ditra or a 5/8" cement board, however if you need a layer of ply, use CDX.

 

[Maciek]

Thank you for all your input. Now, I have a question: what should I use as an underlayment between the CDX plywood and the tongue and groove planks?

 

[Snoonyb]

Nothing, CDX is assembled using exterior grade adhesive products.

 

[Maciek]

Snoonyb, thank you so much for your help!

 

[Snoonyb]

And, the price is right.

Please show the community the process, successes, failures and corrective action.

 

[Maciek]

I will definitely keep on updating my progress in this thread

 

[Maciek]

As promised, I really didn't have much time to work on the project, but I hope to be ready to lay the tile by the end of the week. See the attached photos of my progress. Any input is more than welcome.

 

[Snoonyb]

Thanks, now mark your floor joints on opposing walls, as an index.

 

[Maciek]

Hey Snoonyb,

Thanks for the advice on marking the floor joists. Quick question for you: How long should the fasteners be? Would a 2 1/4 inch long deck screw be sufficient? Also, what would be the recommended spacing between the fasteners? Do you think 8" apart is fine?

Appreciate your guidance!

 

[Snoonyb]

The spacing for the fasteners will usually be dictated by the type and thickness of the substrate employed, IE, 5/8" cement board could allow for a max. 6" OC spacing, where 5/8" CDX would allow an 8" OC spacing, but a 1/2" CDX OR OSB, would allow a 4" OC spacing, in my practice.

For the floor joist fasteners I'd use a min. of 2-1/2" and for the field I'd adjust the length to not fully penetrate the sheeting.

 

[Maciek]

When I place the new plywood on the floor do I leave expansion joints in between or butt them together?
Also if an expansion joint in-between the sheets of ply is needed what do I fill them with before the thinset?

 

[billshack]

it is very important that the floor not move at all . there was a web page that asked question about how far apart the floor joist are and how long are the joist. So that you can install ceramic tile on top with out movement
here is the page just look around for what you need
https://www.johnbridge.com/vbulletin/archive/index.php/t-109507.html

 

[BvilleBound]

First, Bill offered good advice. One key point, however: subfloors and tile floors ALWAYS move, and tile expands / contracts at a different rate than wood. So you need an 'uncoupling membrane', e.g. Schluter Ditra. See: Uncoupling (DITRA) | Schluter

Ditra provides important protection against cracks between tiles, even when the subfloor / framing flexes and the tile expands / contracts.

 

[Snoonyb]

When I place the new plywood on the floor do I leave expansion joints in between or butt them together?
Also if an expansion joint in-between the sheets of ply is needed what do I fill them with before the thinset?

In my practice I butt the joints together, fit them to the space and stager joints. I also never used a decoupling agent, except where the installed product is intended to float.

 

[Maciek]

As promised, i have screwed down the ply to the joists using 2.5" #8 decking screws and also stich ply to the planks in-between

 

[Maciek]

Also later on in the day this happened
Used modified thin set by Shluter

 

[Snoonyb]

Looking good.
The only thing that I would have done differently, is to have screwed the field a 4" OC.