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Jan 15

You CAN, but you MAY NOT!

Posted by C. Mason Hearn in tile, renovation, remodeling, floors, cracks, bathrooms

Hi! We have a early 1930s house. The bathroom has an old tile floor set in cement, with plywood and vinyl laid over the top of this. We want to install a new tile floor. Can we install directly over the vinyl (on top of the plywood), or will this cause cracks? If we take out the plywood, can we tile over the old tile? Thank you!



Dear Mark:

I am reminded of one of my favorite movies, "Avalon", where a kid raises his hand and asks his grammar teacher "Can I go to the bathroom?"  The teacher repeatedly answers his increasingly panicked inquiries with "You CAN, but you MAY NOT!"  Ultimately, the poor kid wets his pants in class.

I am also reminded of how irritating it is when my retired-teacher mother always corrects my grammar, so I hereby profusely apologize to you and offer the answer you seek.

You CAN, but you MAY NOT!  Hahaha.  But seriously...

It is possible to get a job of decent performance out of an overlaid assembly, using the right products and methods.  Most importantly, you should understand that the multiple material layers of various ages and uncertain condition should be assumed to be dimensionally unstable (they move, crack, shrink, swell, and flex), and therefore are not the best substrate, or base, for your tile job.  Tile and tile assemblies are largely rigid, and even the smallest bit of movement may cause them to detach, crack or otherwise fail.

As well, if you keep applying layer over layer of flooring, won't your new tile floor end-up much higher than the surrounding areas?

Accordingly, in order to assure the best new tile job, the preference is to remove everything down to the joists, and start back with new plywood subflooring, tile base and tile.  That is how you'd best assure long-lasting quality in the investment you are about to make.

Otherwise, you MAY overlay the existing work, but would want to be very careful to install appropriate cleavage and crack isolation membranes first, such that your new floor will be isolated from the aforementioned damaging substrate movement, then install an assembly which free-floats on a reinforced backer such as mud or cement board.

There are numerous products and assemblies described by the industry standard Tile Council of North America (TCNA) Handbook (see or your local tile distributor for a copy) for various tile applications.  Whether you eventually decide to overlay existing or start fresh from the joist up, you should absolutely follow the TCNA guidelines.  Tile seems simple, but there is plenty to go wrong if you (or your tile contractor) do not abide by recognized industry standards.

Now, Mark, you may go to the bathroom.  Good luck with your tile job (or whatever else you plan to do in there).


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