Arguing with my dad

Hey,

I am in the middle of my tiling planning and was shooting the breeze with my dad as he likes to do stuff himself as well. He has tiled some of his houses and does good work. Anyway, I was showing hmi my plans for the kitchen and estimation of how much it costs for what I want to do, and noticed that I was spending x amount of dollars for floor prep which includes adding to the sublfoor some BC plywood and some backer board like DensShield. He says why not just tile to the plywood that you add and it would cost less overall? He told me about some plywood made to tile directly on and this would save me money and labor by just adding one layer of floor. I am like, because I read you shouldn't! HAHA. I couldn't reason with him and said "that I read from flooring guys who are knowledgeable about actual tiling standards and not some jack who does something that works and who do it everyday; they all add plywood and a CBU regardless if its a wet or dry area or they won't guaruntee their work or the tile to last." I told him I haven't read anything or heard of the plywood he's talking about that can be used to be tiled directly on.

So what is your answer to this? Why is he wrong which I believe he is but can't make an argument. I did say that I thought the CBU won't have as much expansion as the plywood "would" and this would cause problems for the tile adhesion.

[Curt Durand]

Professional installers who are trained and experienced will usually do a professional quality install that exceeds minimum requirements. Tiling over double layers of plywood can be done but is not the first choice of everyday professionals. Tiling directly onto a DOUBLE layer plywood subfloor is permissible per Tile Council of America TCA Latex-Portland Cement Mortar specifications F147-02 or F148-02 which were written to detail installation over wood subfloors over 24" o.c. or 19.2" o.c. joist spacings (I am sure that 16" o.c. would be OK also) with the use of an uncoupling system - like Schluter's Ditra membrane. Specification F149-02 covered installation over a DOUBLE layer plywood subfloor without an uncoupling membrane - directly onto the plywood. This basically states: over structurally sound EGP (Exterior Glue Plywood) subject to residential traffic with 24" o.c. or less joint spacings, dry areas only, defelection of 1/360 or less, face grain of plywood should run perpendicular to joists, double layer must be 2 layers of 23/32" EGP plywood with 1/8" gaps between sheets and top layer of plywood fasteners should not penetrate into the joists below. Install the tile with latex portland cement mortar ANSI A118.11 spec or better and grout which is ANSI A108.10, A108.6 or better. It can be done and works for many. I've done this with Mapei's Kerabond/Keralastic mortar many times.
Mapei calls for:
Exterior-grade plywood for interior residential floors and countertops in dry areas only. Plywood must be Group 1, CC-type, conforming to APA classification and U.S. Product Standard PS 1-95 or COFI exterior plywood “Select” or “Select Tight Face” conforming to CSA-0121 standard for Douglas fir.
Lots of technical stuff. Sorry.
In short, you can use a double plywood base with the correct mortars and flexible grouts if you want.

Ah, the devils in the tech details...juicy stuff.

I know you pretty much briefed me on this but I am hoping someone can email me TCA's F149-02 so I can read it...I can't find it on the 'net

I am curious, you just pull all of those standard numbers off the top of your head? haha...mad tile setter

So I now realize that this can be done when the standard is followed but it must be a rare breed of tile setter that does it in regular practice. I was reading another forum www.floorstransformed.com and there's this one guy only who seems to prefer that practice of tiling without an uncoupling membrane and everyone else prefers some sort of backer or membrane.

My question is...why is the direct tile to plywood not as popular if in fact it is accepted by the TCA? I sort of guess with my limited knowledge maybe because it appears using a backer or membrane is more forgiving to flaws or nonideal conditions? Not many houses meet the criteria of having a 23/32" original subfloor to begin with?

Mine has a 5/8" subfloor but I would think I would be better off in rigidity by adding 23/32" to that instead of 3/8 or even 1/2" ply with a 1/4 CBU while at the same time avoiding the labor/cost of adding the backer. But I wish to read the spec to see what else is involved and make a decision between the two. I realize the tile on plywood method is riskier in my situation regardless.

I hope I get my plan all sorted out by nest weekend when I plan to purchase everything. I thought I had it all figured out untiil my dad got me thinking about this method. haha...

Brian

[TFP Admin]

Brian,

I removed your email address before approving your message. If you register, other members can email you and you don't have to worry about being spammed or revealing your email address unless you reply to an email. Registering will also allow you to by-pass the approval process and your messages will appear on the forum as soon as you click the submit button.

The TCA publications are quite expensive, I think, and I haven't found them available for free download. There are strict copyright limitations on dispensing the information contained in them, but excerpting portions for purposes of discussion on our forum should be acceptable. Maybe a member who has access to the parts applicable to your situation would be willing to help here.

Thanks,

TFP Admin

[Curt Durand]

Actually the TCA publications are available for a minimal charge. Basically $10 to $20. I use a CD version and can not just copy from it's PDF files. Some information is available online through the Mapei USA website under PRODUCTS, TILE & STONE INSTALLATION SYSTEMS, MOARTAR SYSTEMS| FLEXIBLE MORTARS, KERABOND/KERALASTIC, DATA SHEETS. Specs out the plywood specs and they also have CAD drawings CA2E21, CA2E22, CA2E23 & CA2E24 showing various ways to install tile over plywwod subfloors. These are available online and free.

[TFP Admin]

Thanks for that info, Curt. I was under the impression that some of the publications were quite spendy. Maybe it was another "standard" I was thinking of.

The PDF you were referring to is here: http://www.mapei.it/Referenze/Multim...tic_TDS_EA.pdf

T

[bspaugh]

Alright I registered. I was trying to keep from cluttering up the forum because I will most likely just hang around and "use " you guys, haha until my tiling job is done. After that I probably won't be here as I'll be moving on to something else.

So anyone who wants to email me that F149-02 it would be great. I have access to ANSI standards through Purdue but they don't have any TCA stuff and couldn't find a link through the electronic library.

So with that, I am beginning to change my tune and take the risk of tiling over the ply in this particular job.

So with what I know currently I am plan on:

-renail subfloor to joists
-add 23/32" BCX ply made of fir/sprice with no adhesive between plywood/subfloor and using ringshank screws every 6" flush to surface everywhere while missing joists
-position ply using the locating end joints 1/4 span of joist rule and edge joints at half width of subfloor rule leaving 1/8" expansion gaps
-caulk joints and mesh tape over them during tile setting
-use Kerabond/Keralastic for setting tile

walllah! maybe. haha

[Jerry Thomas]

For a minute i thought you might be Bill Vincent Junior.

Do what you want but I never recommend tiling directly over plywood. I think for 16 OC the rule is two layers of 19/32 with the subfloor having a T&G. If it were me i would be using a CBU or Ditra after some 1/2" BC underlayment.

You will need that Keralastic additive when tiling over plywood.... good pick up on that part.

You don't need us

[bspaugh]

Hey Jerry,

haha...it was hard to find all the details Bill Vincent suggests...most of the threads I read by him he always says, don't do it unless you know what you're doing. Curt Durand opened the door to me for the keralastic stuff anyways.

Anyway I might be changing my mind on this route after I found out how much its going to cost...see my other thread about kerabond/keralastic for suggestions. Thanks!

[Bill Vincent]

Sorry, Jerry-- I'M Bill Vincent Jr.! (ask anyone in the union in Connecticut, and they'll tell you!)

Brian, he didn't open the door for you. He took you part way, and that's worse than nothing at all. You're right-- you DO need to know everything there is to know about setting over plywood, because all it takes is one mistep, and you're done. The floor won't last nearly as long as it should. This is the reason I usually won't go down the list. I can't see the individual floor I'm talking about, and I'd hate to think that by trying to help someone, I actually screwed their floor by not knowing all I needed to know. If you want to go over the plywood and not raise the height any more, do the double layer, and then go over it with something like Noble's CIS membrane. It'll only raise the height of your floor about a 1/16", and you won't have to worry so much about failure.