Hello again,
For those that recognize my user name, we’re still building our house (I’m basically the GC w/ no previous experience). The rough-ins are all done, windows, roof, etc. Getting ready for drywall and had a quick question. We used the Advantec subfloors and are very happy with them considering how much water we got during the framing stage. Now I’m getting ready for the tile installation (approx. 1/2″ thick Limestone tile – 18 x 18) and I wanted to get your opinions. I was thinking of using the Schulter “Ditra” product right over top the subfloors instead of regular 3/8″ spruce plywood. I realize in a perfect world, you would like do both, but I would like to only do one or the other. I’m leaning towards doing the Ditra although it’s a little more costly, it does have a warranty and my tile installer is very experienced with this product and mentioned he nevers has any problems.
Sorry for the extensive detail, but here is my question. Would you use the Ditra product or regular 3/8″ plywood as your tile subfloor if you had a choice? As always, your help is appreciated. Just an FYI – the floor joists are 16″ O.C. and are engineered. Thanks again!!!
Replies
Have you planned the engineered joist span for minimal deflection? Natural stone has the stiffest floor requirement - l/720 (that's a lowercase L) and it's hard to achieve. If you followed the I-joist tables they are usually based on l/420 which is fine for tile but not stone. Also, 18" x 18" is considered a large tile (meaning more difficult to install, very flat floor required) and considering that it is limestone I'd say stone that size isn't normally considered a DIY install.
You ask about Ditra, which is an uncoupling and crack-resisting membrane - it is not intended to be used in lieu of structural subfloor or the correct underlayment, which generally-speaking should be cement board (Durock). There is nothing 'normal' about 3/8" plywood under stone tile.
For more info you might want to check http://www.johnbridge.com
Jeff
Edited 12/30/2007 9:28 pm ET by Jeff_Clarke
So long as your floor system will support the tile w/ the acceptable flex (3/4" Advantec on properly spaced and spanned joists), Ditra is the cat's meow. Use the correct mortars for the install (non-modified under, modified over...or is it visa versa?) and your floor will be a rock.. Far better than a ply underlayment, in any case.
I love Ditra. And I too have never heard of a failure with the product.. Ever.
But just to reiterate - her subfloor/underlayment should be around 1 1/4" total thickness for stone, exclusive of the Ditra.
Jeff
Thanks Jeff. I reviewed the Ditra technical info a little more and you are correct. For stone tile, you need to have to put a minimum of 3/8" plywood on top of your subfloor (min. 3/4"), then you put the Ditra on top of that. If it was ceramic or porcelin you could get a away with just the subfloor. Looks like I may need to pick another tile!
No problem - and as a DIY project you could drop to 12 x 12 porcelain tile which would be a lot easier to set than 18 x 18 stone.
Now can I convince you to use Laticrete SpectraLok Pro grout? ;o)
Jeff