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MJMathews
Tiling bathroom floor with DITRA Underlayment

I am planning to tile my guest bathroom floor with Schluter Systems DITRA Underlayment. This is a plastic mat-like material that is used in place of fiber-cement board underlayment, such as Hardie Backer.
I will install it over a solid plywood floor starting with a latex modified ceramic tile thinset, followed by the DITRA, and then an unmodified thinset to set the tiles in. The tiles are a mosaic sheet of smaller tiles in 12" x 12" sheets.
I have seen it used in This Old House episodes, and it appears to work well. Has anyone had personal experience using this substrate material? Any advice or cautions will be welcome.

huberhouse1886
Re: Tiling bathroom floor with DITRA Underlayment

We used a similar, but different, product in our guest bathroom instead of concrete board. It has worked wonderfully for 5 years and we have no cracks in our grout lines between our 2" tile. DITRA, in my opinion, is top of the line. Should work well if you follow their standards.

Jeanne
Re: Tiling bathroom floor with DITRA Underlayment

Check the specifications for tile size using Ditra. My understanding is that it cannot be used for tiles smaller than 2 inches. I was ready to use it for my bathroom floor when I discovered this and switched to Hardibacker.

HoustonRemodeler
Re: Tiling bathroom floor with DITRA Underlayment

Many of the Tile Pro's on the John Bridge Tile Forum have used Ditra with great success for many years. Myself included.

Sombreuil_mongrel
Re: Tiling bathroom floor with DITRA Underlayment

Hi,
At work we have been using a tile guy who was the first Schluter-schooled special-ist in Loudoun Co, VA, and he sold me on the advantages of that system around 2006. When I was doing my bathroom I used the Kerdi and the Ditra underlayments.
I used a lightly-modified thinset (versabond) for laying them.
I had no problems using small tiles on the Ditra (my feeling is with Ditra XL, I'd respect the manufacturers judgement on not using small mosaics). On his advice, I floated thinset into the Ditra grid-voids the day before I laid the tile, so there was a solid continuous surface for the mosaics.

Casey

kmoyer01
Re: Tiling bathroom floor with DITRA Underlayment

I have Ditra in my bathroom and kitchen. It works wonderfully, but I'm relatively sure it can't be used with 1" tile. Go to Schluter's website, they have detailed instuctions for every installation application imaginable. That being said, you may be able to use sheets of Kurty instead of Ditra if you are just looking for the waterproofing qualities. I have never attempted this though and would still ask Schluter (also makes Kurty) about the possibility.

maplemale
Re: Tiling bathroom floor with DITRA Underlayment

This is the first I've heard of this stuff...

So, how strong does my sub-floor need to be? My test which has served me well over the years: If a 200lb guy can jump up and down on the hardiebacker, and it doesn't give / move at all, I'm good for tiling it. Usually I end up with 3/4 inch subfloor and hardiebacker. If my subfloor is something in the 5/8- range, I end up having to supplement it with more sub-floor and possibly blocking between joists to get the zero movement.

I guess my question is, how does a DITRA underlayment help with any of that? Or does it? For instance, I can a get away with a 3/8 subfloor on 16 inch center joists or even TJs if I'm using this stuff? Or, is just a little bit of extra protection on top of my stable subfloor in place of hardiebacker? If that's the case, then it seems like it's more expensive and doesn't provide a whole lot of extra benefit?

HoustonRemodeler
Re: Tiling bathroom floor with DITRA Underlayment

The bare minimum plywood over 16" OC joists is 5/8" T&G but most Pro's would prefer 3/4" T&G. In either case, the plywood must be exterior glue, not 'sheathing', oriented with the face grain perpendicular to the joists, and be properly secured to the floor.

Ditra and ceement board have no effect of between joist deflection, nor joist deflection.

The minimum joist deflection for ceramic and porcelain tiles is L360. The bare minimum for natural stone is L720. Natural stone tiles also requires two layers of plywood at least 1.25" thick.

Jumping up and down isn't a TNCA approved method.

You'll find answers to all questions tile related, along with a user friendly Deflecto-meter at the John Bridge Tile Forum.

maplemale
Re: Tiling bathroom floor with DITRA Underlayment
HoustonRemodeler wrote:

The bare minimum plywood over 16" OC joists is 5/8" T&G but most Pro's would prefer 3/4" T&G. In either case, the plywood must be exterior glue, not 'sheathing', oriented with the face grain perpendicular to the joists, and be properly secured to the floor.

Ditra and ceement board have no effect of between joist deflection, nor joist deflection.

The minimum joist deflection for ceramic and porcelain tiles is L360. The bare minimum for natural stone is L720. Natural stone tiles also requires two layers of plywood at least 1.25" thick.

Jumping up and down isn't a TNCA approved method.

You'll find answers to all questions tile related, along with a user friendly Deflecto-meter at the John Bridge Tile Forum.

No clue what TNCA is or why I should care. I've seen dozens of professional tile installers bounce test a floor like that. It doesn't hurt. I don't care if your little calculator says everything should be perfect and you have 3/4 T&G on full 2" joist at 16" centers etc. etc. If I can jump on it and it bounces it's going to crack tile / grout - period.

Anyway... by T&G I'm assuming you mean OSB T&G. Also, I'd have to completely disagree on cement board having no affect at all on deflection. It might not have a ton of affect. But, it does indeed effect it. Simple physics / engineering there. So, i'm not sure I buy it when you talk about DITRA having no affect... and if it has no affect other a more expensive moister barrier, then why use it?

HoustonRemodeler
Re: Tiling bathroom floor with DITRA Underlayment

TCNA is the Tile Council of North America which sets the industry accepted standards for setting tile, making tiles, along with installation methods and materials. They've been printing these guidelines for 50 years. Recently they have incorporated natural stone and glass tiles. The TCNA works side by side with ANSI, the UPC, and international bodies of related industries.

Ditra isn't waterproof on its own. To achieve waterproofing, the sheets must be seamed with kerdi band as prescribed by Schluter. Ditra does offer some measure of in-plane sheer movement protection, which is its main claim to fame for the last 27 or 28 years. There is no membrane which offers protection from vertical displacement. Ditra is used to replace CBU for several reasons; moisture management, thickness (DitraXL for example) labor savings, weight savings, speed of installations, and integration into an overall waterproofing system such as balconies or decks.

All of the manufacturers of CBU's agree that ceement backer boards add nothing to the reduction in deflection. Visit their websites to double check if you'd like. You will find no such claims of reducing deflection even when properly installed.

If you want to discuss the measurable, scientific standards for the "Jump Test" I'd be happy to do so. But please, for the sake of the DIY folk reading along, do not try to pass the Jump Test off as some sort of industry standard which they should find acceptable, even if you do.

maplemale
Re: Tiling bathroom floor with DITRA Underlayment
HoustonRemodeler wrote:

TCNA is the Tile Council of North America which sets the industry accepted standards for setting tile, making tiles, along with installation methods and materials. They've been printing these guidelines for 50 years. Recently they have incorporated natural stone and glass tiles. The TCNA works side by side with ANSI, the UPC, and international bodies of related industries.

Ditra isn't waterproof on its own. To achieve waterproofing, the sheets must be seamed with kerdi band as prescribed by Schluter. Ditra does offer some measure of in-plane sheer movement protection, which is its main claim to fame for the last 27 or 28 years. There is no membrane which offers protection from vertical displacement. Ditra is used to replace CBU for several reasons; moisture management, thickness (DitraXL for example) labor savings, weight savings, speed of installations, and integration into an overall waterproofing system such as balconies or decks.

All of the manufacturers of CBU's agree that ceement backer boards add nothing to the reduction in deflection. Visit their websites to double check if you'd like. You will find no such claims of reducing deflection even when properly installed.

If you want to discuss the measurable, scientific standards for the "Jump Test" I'd be happy to do so. But please, for the sake of the DIY folk reading along, do not try to pass the Jump Test off as some sort of industry standard which they should find acceptable, even if you do.

Please for the sake of DIY folk reading along, don't go on random DIY forums and attempt to sound high-headed for no other purpose than to sound correct about everything. There ya go. We can each make plea's and since neither of us are admins we are both free to ignore them. What a waste of words.

One can say something is fecal matter by conducting a mass spectrographic analysis on it, or one can just see if it smells like fecal matter. Both are technically scientific methods of testing to see if something is fecal matter. If you can jump on your sub-floor and it visibly bounces / flexes up and down within a 1-2 foot area around your feet, you're going to have cracked tile or grout sooner rather than later. It is an easy / DIY test and to say the least does not hurt anything. At best it is a final "smell test" to see if your installation stinks or not. I have used dozens of professional tile installation contractors in my state and most of them advocate doing this.

Thanks for the info on the Ditra. After reading everything you've written about it and reading up on their website / watching installation videos etc., it seems like it suites very specific scenarios better than CBU. But I don't see how it could save time or labor costs as a general replacement. Seems a lot more complicated of an install process than using cement board which everyone is familiar with. In any case I'll withhold judgement till I've used it.

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