OSB or Plywood under ceramic tile

[ravenbreeze]

After reading and reading and reading all I can find online.......I'm more lost and confused than I was before I began! Our home recently burned and my teen dau and I are "remodeling" a new space. I intend to lay ceramic tile but most sites and ppl at home improvement stores state you should not, under any circumstances, lay ceramic tile on plywood or OSB.
I have wood 2X4X10 floor joists spaced 24" apart, I plan to "sister" the joists to add some stability, should I do more? I will also be adding insullation (altho I don't suppose the insullation will affect your responses & hope it doesn't affect the job I'm doing adversely). Wonderful ppl in the area have donated both 3/4" plywood(not treated) and 3/4" OSB(not treated), insullation, and the the tile, thinset and grout. Should I lay the OSB first then the plywood or the plywood and then the OSB? Should I use nails or screws and how far apart should I place them? Should I treat the plywood and/or OSB with some type of water repellent, if so should I treat top bottom as well as sides?
I have never tried to lay tile before and hope for the best, any info or tips you care to provide will be greatly appreciated. Due to the house burning to say I'm a shoestring budget would be stretching the truth pretty far, my budget is nonexistant, I will basically have to work with what I have and hope for the best altho I do believe I may be able to come up with some type of water repellent. I would hate for all that tile to pop up, or crack and most of what I've read and been told is that that is what will happen.
I have ceramic tiles that are 6"X6", 6"X12", 12"X12" and 18"X18". I plan on beginning in the kitchen and will also tile the bathroom and possibly the livingroom. There are no cabinets & no appliances, I've stripped and removed everything down to the joists. After reading your posts and responses for days on end I think I've put the info needed above. I'm sure you get tired af answering the same questions repeatedly and I have read pretty much all that's posted incl the 'sticky' hopefully I haven't repeated to many questions.
Thank you for your help and time,
Marilyn[/i]

 

[gcol]

Hi Marilyn,
Do not tile onto OSB - it has no integrity.
It is rarely done, but if you want to do the job properly, give the bottom and sides of the ply a coat of fence preservative before you fix it down. Do not coat the surface to be tiled though.
Screw the ply down about every 10".

 

[ravenbreeze]

Hello gcol, thanks for the response.....should I use the OSB under the plywood or will the 3/4" plywood be ok alone? The only thing between the ceiling and the ground at this point are the floor joists. I read that the plywood should stop 1/4" away from walls when tiling, if I do this I would need the OSB underneath or some type of silicon caulk I suppose? The 3/4" + 3/4" may be overkill or may just give me whats needed to bring it up to the thickness preferred by most. What kind of lifespan am I looking at w/using the plywood under the time, do you know?
I'm new to any and all diy such as this, so I'll ask some stupid questions, but plz bear with me.
Thanks
Marilyn

 

[Symptoms]

Marilyn - I reckon you're going to have to beef-up the structure of that floor to eliminate any flex; those 2" x 4" joists, even after 'sistering' with additional stuff, may still move causing your ceramic tiles to crack. Any chance of installing some wooden props below to add vertical stability (prevent bounce)?

24" centres on those joints will also allow your ¾" ply to flex - this will also result in cracked tiles - so increasing the thickness of this deck will eliminate this risk. Usually, with bigish joist spans you should use at least 1" ply, but as you are can't afford to do this and have a load of donated sheet material, I'd be tempted to screw the OSB down first then overskin with your ply. Glue the top layer of ply onto the OSB using a polyurethane adhesive (you can get it in cartridges to fit a skeleton gun) then screw (through the OSB & into the joists). Apply the glue as a 'zig-zag worm' over the OSB.

Does your part of the US suffer badly from timber pests (termites, etc.) ... if so make sure you spray the timbers with whatever is recommended for your locality.

 

[ravenbreeze]

Hello Symptom,
I don't seem to have loads of termite damage unless the thiefs of the county can be called termites, in fact none of my wood is damaged beyond water damage it seems. There is a metal frame upon which the lot rests and approx every 3-4' there is a metal brace that runs front to back, the 2x4s rest on this brace system and are secured to the metal frame.
Yes, I could add supports under the 2x4s ~ since I pulled/tore up all the flooring & cabinetry it's all open. Should I put down blocks or cement then place the supports on it maybe, I have a couple of bags of quickrete? I will get the adhesive and use it between the OSB and plywood after I get it all nice and rigid............and get some tools back. Seems someone was in more desparate need than I and they helped themselves to my mikita saw, 4' metal carpenters square, smaller square, and a few other odds and ends. All the tile, plywood, OSB, 2x4s and such were left behind maybe they were to difficult to tote, so that's the upside and a great upside it is indeed! Would have been really upsetting to find the lot gone.
Sorry about the incomplete info I posted first. It never entered my mind to add a support system from underneath this is going to be a good week ~ I can just feel it in my bones. I'm finally getting some answers besides, "little lady you just can't lay tile on plywood......" When I take my dau w/me to ask about this stuff, which is 95% of the time, I really get negative replies. I suppose they see a 5'3" 98lb little girl and a not so much bigger mother and think we're nuts or something. They'd be surprised at the strength that "little girl" has within her.
Thanks
Marilyn

 

[Symptoms]

Marilyn - seem like the steels you have below may solve any flexing of the joists - you can test for this. Get a very long straight-edge (a length of STRAIGHT timber), hold this touching below the joists, get your Dad (is he fat?) to jump on a section of ply (loose) laid over the joists. Look for deflection ... there shouldn't be any if you want to lay ceramic tiles. Any flexing then install a couple of props.

 

[ravenbreeze]

Symptom ur funny! I can round up a heavy person or two, my dau and I combined weigh in at around 120lbs, that's probably not heavy enough? I was wondering how to test the floor for 'bounceability' or whatever the tech name is for it, I got an answer and a laugh. Thank you!
~Marilyn

 

[ravenbreeze]

correction: that would be 220 lbs
~Marilyn

 

[roughcaster]

8)

 

[cantaloup63]

delete

 

[joe-90]

Maybe Roughcaster's on drugs?

 

[roughcaster]

No,,not on drugs guys,,, it's ok,, i reponded to that post from Williamsyorks. He wrote it tonight about six o'clock. It didn't make sense and that's why i replied that way. It had an advertising weblink attached, along with 5 other posts he made. All of the other topics were 3 years out of date too.
With the mods deleting his reply, it's made my reply look as though i've gone doo lally,, although some might say i've been that way for years. I'm going to edit that reply away now.

 

[Richard C]

With the mods deleting his reply, it's made my reply look as though i've gone doo lally,, although some might say i've been that way for years.

We have all been caught out & I don’t for one minute think you’ve lost it; you’re still a star in my books RC

 

[cantaloup63]

delete

 

[roughcaster]

Of course your editing out only holds water if I edit my post too

I'll give you a fiver then!!