Prepping floor for ditra??

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Old 07-17-10, 02:23 PM
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Prepping floor for ditra??

So, I'm starting my next tiling project... tiling just about the entire downstairs to our place-~550ft^2. I'm going to be doing one room at a time over the next couple months and I've got some questions...
About 450 ft^2 of the soon to be tiled area has sheet vinyl adhering to it (it's adhered directly to 5/8" ply underlayment which is sitting on top of 5/8" subfloor) The Ditra manual says its ok to tile over it, but from what I've read, that's not the practice. So, my plan is to rip up the vinyl , try to rip up as much glue as possible then lay down 3/8" ply, then Ditra. Does this sound ok? Is there a better way?? Can CBU be laid down over vinyl such that it'll be a lasting install?
Next, I'm starting with my front entry and there are a couple dips. Do I need to SLC before adding the 3/8" & ditra or do it after installing the 3/8" underlayment?
Thanks
 
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Old 07-18-10, 05:33 AM
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Actually.... In peeling up some of the vinyl last night, I see that unlike the bathroom I did a few months ago, this stuff is just perimeter bound and is coming up nice and clean. So, unless I hear that it is absolutely necessary, I think I'm going to nix the 3/8" underlayment.

BUT, are there any brand recommendations for self leveling compound? Any that I should steer clear of?
Thanks
 
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Old 07-21-10, 09:05 AM
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Suziq

The 5/8" subfloor and 5/8" underlayment is good. You don't need to add another 3/8" plywood.

BUT, are there any brand recommendations for self leveling compound? Any that I should steer clear of?
Thanks
I only use TEC, but all manufacturers make good slc's. Basically, it has to be a portland cement based slc. How do you know you need slc? Have you checked the floor for flatness? Can you tell us what you have there?
 
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Old 07-21-10, 09:30 AM
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Originally Posted by HeresJohnny View Post
Suziq
How do you know you need slc? Have you checked the floor for flatness? Can you tell us what you have there?
Hey Johnnie! Yes, I have checked the floor for flatness and there are two spots (where all the foot traffic has been) that dip down. One dips a little more than 1/4" and the other just under 1/4", but over the 1/8" I was previously told to look for.
Other specs-14 y/o house w/ 16"OC joists, possibly TNG ply for the subfloor. I'm installing 12" porcelain tile over Ditra. Starting in my floyer/entryway and will be working on tiling just about the entire downstairs area over the next couple months.

While I've got folks attention... Another question... The Ditra manual says there needs to be 1/8" spacing between the subfloor sheets..... Does that mean the long side of the ply (going with the grain) or the short side or both. The stuff that's there now, there's barely 1/16" in most spots on the short side.
Thanks I really appreciate the help!!
 
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Old 07-24-10, 04:23 PM
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I doubt the dips in the traffic areas were caused by the traffic. If so, you've got other issues. Hopefully your subfloor was also spaced an 1/8" (all sides of course), as required by common carpentry practice. Sheets shrink and expand most the long ways, therefore the short ends show most of the movement. Maybe yours has expanded and so the narrow space.

The subfloor flatness spec for standard tile is for it to be in plane within 1/4" in 10 ft. AND 1/16" in 12" of required plane. If the tiles are large or shiny and smooth I would want within 1/8" instead.

Make the floor flat before you install Ditra.

Jaz
 
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Old 07-26-10, 02:54 PM
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Thanks Jaz What you're saying about the subfloor being expanded makes sense... It's only been ~100F w/ 90%+ humidity here in SC!
Picking up SLC from the tile store in the morning and it'll hopefully be nice and flat by Wednesday
 
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Old 07-26-10, 06:28 PM
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Makes sure you have enough SLC on hand and be ready cuz you don't have much time once it's mixed. Although it's called self leveling, it doesn't really work that way. Usually self leveling cement need some help flowing. Don't forget the primer.

Jaz
 
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Old 07-26-10, 07:30 PM
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Originally Posted by JazMan View Post
Makes sure you have enough SLC on hand and be ready cuz you don't have much time once it's mixed. Although it's called self leveling, it doesn't really work that way. Usually self leveling cement need some help flowing. Don't forget the primer.

Jaz
Right The folks at the tile store put the primer in with my order as well
Thanks Jaz! I really appreciate the help
 
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