Novice Tiler [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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09-12-2001, 01:15 PM
My wife and I plan to install 13"x13" porcelain tile in a small breakfast area (9.5'x11'). The subfloor is 3/4" OSB over 2"x4" open-web trusses at 24" on center. Would a layer of 1/4" plywood and a layer of 1/4" Hardibacker be a sufficient substrate? Also the OSB has "bucked" in areas where it is attached to the trusses. How should I deal with this situation. All help is appreciated.

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John Bridge
09-12-2001, 03:55 PM
Hi Rick, glad you found us.

There are varying opinions about OSB. My opinion is that it is terrible. My vote (which is far from final) is that you remove it and start over on subfloor. I dearly love the open web trusses, on the other hand.

More opinions will follow. :D

Rob Z
09-12-2001, 08:08 PM
Hi Rick

The builders here in VA have forgotten what plywood is and use OSB for everything. They deal with the inevitable moissture induced swollen edges by gringing them down after the house is closed in. I have OSB throughout my entire new house, and it feels solid as can be. I had the builder put vinyl in, because I don't think cement board should go right over OSB. When it comes time for me to do tile in my own house, I will mud the floors.

If mud isn't an option for you, then I would add 3/4"T&G plywood, with DITRA over that. Schluter DITRA is the only product I know about designed for use over 24"oc joists.

Rather than go through the time and efort to tear out the OSB, only to need a second layer of subfloor anyway, I would save that time and money to spend on the DITRA.

Brian and I have both have had good experiences with DITRA. Read about it at Schluter's site:

Direct specific Q's to Peter Nielsen, technical director.

Come back and see us and let us know what you think.