# Removing old thinset from subfloor



## JazMan (Feb 17, 2007)

Maybe you just misspoke, but are you saying your old 1x1 tiles were installed direct to the subfloor? Are you sure that layer of plywood isn't the 2nd layer or the underlayment? Please double check that. If there are 2 layers, and that top layer is 1/4" thick, remove it. 

Let us know what you find. While you're at it, you should confirm that the joists system is stiff enough. Let us know the; type and size of the joists, their spacing, and the unsupported span. It would also be helpful if we knew the species and grade too. 

Jaz


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## gburg3 (Dec 14, 2008)

*1 layer*

Well they did lay the original 1 x 1 on the subfloor. Below the 5/8" plywood is insulation. As far as the joists system, the house has a crawlspace so i guess I can look there. I'm very novice at this so when I go under what should I look for exactly? Really appreciate your patience.



JazMan said:


> Maybe you just misspoke, but are you saying your old 1x1 tiles were installed direct to the subfloor? Are you sure that layer of plywood isn't the 2nd layer or the underlayment? Please double check that. If there are 2 layers, and that top layer is 1/4" thick, remove it.
> 
> Let us know what you find. While you're at it, you should confirm that the joists system is stiff enough. Let us know the; type and size of the joists, their spacing, and the unsupported span. It would also be helpful if we knew the species and grade too.
> 
> Jaz


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## JazMan (Feb 17, 2007)

OK, you installed the old tile direct over the subfloor, 5/8" plywood no less.:huh: Now it's removed, please don't do that again. 

As you may have guesses, 5/8" plywood is the very minimum allowed for a subfloor in residential floors. I would not recommend installing tile over Ditra or a cement backer on such a flimsy subfloor. I recommend adding an underlayment or at least 3/8" prefer 1/2" or thicker, then Ditra or a backer. 

You will read that many manufacturers give their blessings installing their membrane or backer board over 5/8" plywood. But such claims are always followed by the fine print that the construction must meet IRC and local codes for max deflection of L360. Believe me 5/8" plywood subfloor is nothing to brag about unless the joists spacing is reduced from the normal 16" to maybe 12". That is rarely done.

Sounds like you don't know what a "joist" is? Joists are the long 2x8 or 2x10" (sometimes 2x12"), boards that support the house. The unsupported span is the distance between the two support they rest on. Often the outside wall and a center I beam. 

OK, being a complete novice, do you plan on doing this work yourself? Have you chosen the tiles, setting materials? 

Jaz


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