View Single Post
Unread 07-26-2021, 03:54 PM   #4
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

Join Date: Jul 2004
Location: Nashua, NH
Posts: 15,083
Tiling requires the structure to be stiff enough, and that's what the 'Deflecto' tool can help you evaluate. Then, a significant part of that is how strong the subflooring is so that the structure in BETWEEN the joists can be stiff enough. The modifiers in thinset are more to help with seasonal dimensional changes and differences between dissimilar materials...not so much to help with deflection. That's one reason why a modified thinset is required to succeed in bonding tile directly to plywood. You can overcome that issue if you use some intermediary substance, like a cement board, or suitable membrane to decouple the two.

FWIW, to successfully tile directly to plywood requires TWO layers of plywood, both installed properly over joists that meet industry standards.

If the backs of the tile retain a solid coat of thinset, that implies that at least the workmanship of setting them was down well, but the materials used or the structure was not sufficient to support tile long-term. Other things that can cause an install to fail are things like improper or missing expansion joints, and the tile can break bonds due to tenting issues.

Without knowing more, it's impossible to say why yours failed.
Jim DeBruycker
Not a pro, multiple Schluter Workshops (Schluterville and 2013 and 2014 at Schluter Headquarters), Mapei Training 2014, Laticrete Workshop 2014, Custom Building Products Workshop 2015, and Longtime Forum Participant.
jadnashua is offline   Reply With Quote