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topsurvivor
10-11-2006, 11:21 AM
Can I use Ditra over backer board? What type of thinsets between layers? I read a study on Schluter-Ditra that said unmodified was stronger between both layers: the CBU and Ditra, and Ditra and tile? Didn't know that--did any one else?

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MarcusEngley
10-11-2006, 11:24 AM
You can use Ditra over backerboard on the floor, but what are you trying to accomplish? If the backerboard is already thinsetted and screwed down, you can just tile over that...

topsurvivor
10-11-2006, 05:32 PM
Hi Marcus--

Long story, but tile guy wants to use backer board because subfloor not rea level, but I already have Ditra, and would like to use it for the uncoupling and waterproof effects, so I wanted to know if I could use both. I've also read some contrary opinions on what type of thinset to use. Ditra implies :) unmodified is best for both layers, but others have said modified under the Ditra and unmodified under the tile. Also, does mortar go under backer board. Tile man wants to use thinset at tub edge with caulk over it, I've read that silicone is best to use Help?

Thanks again.
top

MarcusEngley
10-11-2006, 05:44 PM
Not sure what the tile man wants with the thinset at tub edge followed by caulk... can you 'splain more?

CBU isn't going to do much to level your floor if it's not level now -- with the thinset underneath and all the screws, it sucks down to about the same shape/non-levelness. It might smooth out *little* bumps, but not much more, from what I hear.

Won't hurt none to use both, but you definitely want thinset under the CBU and make sure it goes down with CBU screws. I used Versabond grey above and below my Ditra -- it's very lightly modified and not real 'spensive...

igneous
10-11-2006, 07:51 PM
If you want to use your Ditra, then forgoe the backerboard and do a self levelling compound (SLC) pour. I think the best way to do an SLC pour is to use some type of membrane over top of it and if done correctly will provide a level surface. Take the money you were going to spend on backer and put it into SLC. You may spend more than that, depending on how bad it is.

Brad