Can I tile over OSB?

many_hatsFebruary 16, 2009

WeÂve removed our old ceramic tile floors in the 2 upstairs bathrooms and are thinking of having 13" porcelain tiles with 1/8" grout lines installed for the new floors. We have 5/8" tongue-and-groove fir plywood then 7/16" OSB glued and screwed to the plywood. Two tile guys who gave us quotes have no issue with that but one guy said that he never installs over OSB and wants to put down Ditra. From looking in the GW archives and a couple of forums I see no mention of OSB Â mainly plywood, CBU, and Ditra or other membranes. If we install the tile over the OSB are we asking for problems?

Thank you for reporting this comment. Undo
mongoct

You can tile over plywood (proper grade of ply) because the proper thinset will bond with the continuous layer of wood veneer.

When tiling to OSB, the thinset has to try to bond with wood strands or wood chips, and the resin or binder that holds the chips together. It won't get a bond strong enough to deal with the stresses of a direct OSB-to-tile installation.

That's where a membrane like Ditra comes in. It'll act as an intermediary between the tile and the OSB.

So no, you shouldn't tile directly to OSB. I don't believe and governing or guiding agency allows or recommends it.

Mongo

    Bookmark   February 16, 2009 at 10:32AM
Thank you for reporting this comment. Undo
many_hats

Thanks Mongo for such a quick reply and also for the explanation of WHY OSB isn't good to use. We'll add the Ditra now. Thanks so much for your expertise--it's very much appreciated.

    Bookmark   February 16, 2009 at 11:26AM
Thank you for reporting this comment. Undo
mahatmacat1

Man, you can just put down ditra over osb and tile over it?!

I'll have to file that info away for my *next* house. Would have saved us a lot of time LOL

    Bookmark   February 16, 2009 at 3:14PM
Thank you for reporting this comment. Undo
mongoct

Yup.

Ditra over OSB is o-tay.

Your "next house?"

You mean your "weekend getaway" right? After all your efforts would you consider selling your place?

    Bookmark   February 16, 2009 at 5:45PM
Thank you for reporting this comment. Undo
bill_vincent

Yup. O-tay, Buttwheet!!

    Bookmark   February 16, 2009 at 9:14PM
Thank you for reporting this comment. Undo
roxyl

Would Ditra work over chip or press board? It's all over our kitchen and bathrooms (there's vinyl currently there). Blech. If so, any hints or tips?

    Bookmark   February 16, 2009 at 11:01PM
Thank you for reporting this comment. Undo
bill_vincent

Take up the pressboard. It WILL NOT work with either of those, due to the fact that they expand way too much when they get wet, which would cause the tile to pop, and it wouldn't take to long to happen, either.

    Bookmark   February 17, 2009 at 7:33PM
Thank you for reporting this comment. Undo
davidro1

I used Kerdi (instead of Ditra) in a 6 sq.ft. area since it kept floor height aligned. Hope that was ok. The tiles were 2 sq.ft. each. Then I epoxy grouted.

-david

    Bookmark   February 18, 2009 at 9:54AM
Thank you for reporting this comment. Undo
mahatmacat1

O-tay? We're definitely aging ;)

Mongo, we aren't selling...it was more a rhetorical 'next house'. We're not planning to sell until DD goes to college (about 7 years from now), and may not then unless we find something we really like better. As I'm sure you know, after all this customizing work one tends to get very picky :)

    Bookmark   February 18, 2009 at 12:11PM
Thank you for reporting this comment. Undo
weedyacres

I agree with the experts, and would always use an underlayment, but have seen it done otherwise. We tore out our foyer and it was tiled directly to the OSB. No cracks or anything--it had held up fine--but we laid Ditra before we tiled.

Exhibit 2: Mr. Weedy fixed his Chiropractor's office floor, which had some tiles cracked. He went into the crawl space and found the OSB had sagged at a seam, so he braced it up and re-laid tile over the bad spot. The Chiro didn't want the whole floor torn out, so he laid it directly on the OSB. I told Mr. Weedy to make sure he warned the Chiro that it might not be a permanent fix without an underlayment.

    Bookmark   February 19, 2009 at 8:22AM
Thank you for reporting this comment. Undo
many_hats

Now the issue we've run into is that if we lay Ditra, it will raise the bathroom floor above that of the hallway (which we'll do and use a transition strip if there are no other alternatives--adding a layer of plywood would raise it also).

A tile guy is looking into whether there is a "primer" (his words) that can be applied over the OSB to not increase the floor height. I'm wondering if that is perhaps Redguard.

What about using Kerdi like davidro1 referred to above in his post? If that's usable, how much does it raise the floor?

So, are there alternatives to Ditra that won't the raise the floor height as much? Many thanks again...

    Bookmark   February 27, 2009 at 8:58AM
Thank you for reporting this comment. Undo
bill_vincent

Deal with the transition. DO NOT shortcut the floor composition. Trust me on this-- it'll come back to bite you. There is no way you can safely tile directly over OSB. There is no bond coat-- not Redgard, Not Ultraset, Not 9235-- nothing-- that will help.

    Bookmark   February 27, 2009 at 9:07AM
Thank you for reporting this comment. Undo
mongoct

Kerdi, while waterproof, is not an isolation membrane. It's too thin to offer any shear resistance between adjacent materials.

Ditra is only 1/8" thick. But the structure of that thickness is what allows it to absorb stresses and decouple the subfloor from the tile.

Mongo

    Bookmark   February 27, 2009 at 2:23PM
Thank you for reporting this comment. Undo
many_hats

Thanks so much Bill and Mongo for your quick and informative replies. You guys are so wonderful!! We'll definitely go with the Ditra. This information makes it sooo much easier when dealing with the tile guys' suggestions.

Thanks again.

    Bookmark   February 27, 2009 at 2:53PM
Sign Up to comment
More Discussions
Textured tile on the floor of shower for safety?
I read this suggestion somewhere, has anyone used this...
prairiemoon2 z6 MA
amerec vs mr steam vs thermasol steam shower
Trying to choose a steam shower for a 4 x 5 shower...
panchoandlefty
Polished vs Unpolished tile for bath
We are redoing our master bath with a grey 12x24 porcelain...
btnik
Cast Iron, Soaking, Free Standing Tub?
That is what I think I want, but I'm not finding very...
prairiemoon2 z6 MA
Toilet seat height
The other thread here asking about whats new in bathroom...
numbersjunkie
© 2015 Houzz Inc. Houzz® The new way to design your home™