# First time using Ditra, questions....



## ApgarNJ (Apr 16, 2006)

I've been reading some threads on here about Ditra and I'm finishing up a bathroom remodel next week, once the subs get done doing their wiring and plumbing. 

I want to use Ditra over the new subfloor I just installed in the bathroom. It's going to be 12" sheets, each sheet will have 4" octagon tiles on them. 

I know I need to use modified thinset over the subfloor ply and then unmodified between the tile and ditra. 

Having never installed this before, I just have some questions about what size trowel do you use to install the ditra(not XL) over subfloor, and then what is the best tool to use to smooth it out once you have it precut and thinsetted down?

for setting the tiles described above, I would normally use a 1/4 x 1/4 notched trowel, will the ditra require using a 1/4x1/2 trowel since it has so many spaces to fill in as you tile on top of it?

I'd also like to know the best tool to cut it, util knife? snips? 

when coming up to a tub edge, how do you keep that a water proof seal where the ditra meets the tub? or can silicone be used once the tiles are set and grouted. 

This is for a beach house and doesn't get used as an everyday shower, even in the summer, the outdoor shower gets used the most. 

I've been putting off using ditra for long enough and really want to use it from now on. I may even use Kerdi for the shower/tub walls. 

a few questions about that, Unmodified from kerdi to drywall? best tool and angle to smooth it out, I'm afraid I'll either put too much behind the kerdi or scrape too much off when smoothing it off. what sized trowel to use when applying the thinset to the drywall/wallboard prior to putting the kerdi on. 

when you seam kerdi in the corners or even on a flat wall, do you put thinset between the lap of kerdi (3 inch lap ok?) ? if not, what is used to stick the laps. Will the kerdi actually stick to the cast iron flange edge of the tub when thinsetted on?


Sorry for all the questions. I found random threads about these items but never all the questions answered together in one place. 

If this has already been answered, I apologize.


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## angus242 (Oct 20, 2007)

I know I need to use modified thinset over the subfloor ply and then unmodified between the tile and ditra. 
*Correct. Consider using a liquid latex additive so you only need to purchase 1 kind of thinset, non-modified. I always use Kerabond + Keralastic for my modified. Then the Kerabond + water over the Ditra. *

Having never installed this before, I just have some questions about what size trowel do you use to install the ditra(not XL) over subfloor, and then what is the best tool to use to smooth it out once you have it precut and thinsetted down?
*I install Ditra with a 5/16" v notch. That should be readily available. The official Ditra trowel is actually 11/64" x 11/64" square. You can use a rubber grout float, wooden trowel or even a 2x4 to smooth it down. I like to walk over the surface too.*

for setting the tiles described above, I would normally use a 1/4 x 1/4 notched trowel, will the ditra require using a 1/4x1/2 trowel since it has so many spaces to fill in as you tile on top of it?
*No special trowel necessary. Use what you normally would. Just prefill the waffles either the day before with the flat side of the trowel or before spreading with the notches.*

I'd also like to know the best tool to cut it, util knife? snips? 
*Simple utility blade. Just make sure it's sharp. Cut slowly until you get the feel of how the waffles will want to "guide" your cutting. You'll understand the first time you trying cutting a straight line.*

when coming up to a tub edge, how do you keep that a water proof seal where the ditra meets the tub? or can silicone be used once the tiles are set and grouted. 
*Set the Ditra as close to the tub as possible. If you don't install tile the same day, throw a bead of silicone before you tile. You will also silicone that gap after tiling too. *

a few questions about that, Unmodified from kerdi to drywall? best tool and angle to smooth it out, I'm afraid I'll either put too much behind the kerdi or scrape too much off when smoothing it off. what sized trowel to use when applying the thinset to the drywall/wallboard prior to putting the kerdi on. 
*Unmodified always with Kerdi. I use an 1/8" x 1/8" square when installing Kerdi. You can use 1/4" X 3/16" V notch. You do need to be careful to not squeeze out too much thinset. For 1 you won't get proper adhesion but also, if you put too much behind, when you flatten the Kerdi, you can get too much ooze coming out. That can get messy.*

when you seam kerdi in the corners or even on a flat wall, do you put thinset between the lap of kerdi (3 inch lap ok?) ? if not, what is used to stick the laps. Will the kerdi actually stick to the cast iron flange edge of the tub when thinsetted on?
*You should use Kerdi-Band to seam the Kerdi. Band is half as thick as Kerdi. If you lap Kerdi over Kerdi you may get too much membrane build up. It can cause a "hump" to tile over. The Kerdi-Band is the perfect size to treat the seams. You do not thinset Kerdi to a tub flange. You would use Kerdi-Fix to anything other than your wallboard material.*


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## JazMan (Feb 16, 2007)

Hi Dan,

You'll like using Ditra. 

* Use modified thin set to install Ditra over plywood.
* Use a high quality unmodified to install all tiles including porcelain, (which normally require modified).
* The official best trowel is 11/64 square notch, close to 3/16. 5/16 V is good too. I use a wooden float to beat it in & work out air bubbles.
* Use what ever you'd use on a flat substrate. Think about it, the dove tails are lower, the tiles still sit the same way. With most oct. mosaics that I see, 1/4x1/4 is too much. Maybe yours are thicker.
* Cuts with a utility knife.
* Seal the Ditra/tub crack with silicone, then again after tiles are set. You can use regular caulk if you'd rather avoid the silicone mess.
* Kerdi is great stuff too, good idea around a tub. Great idea for showers.
* Use quality unmodified with a 1/8" square trowel to install Kerdi to wall board and same thin set with appropriate trowel for tiles. 
* I use a cement finishing trowel to push air out, sometimes a wide putty knife. 
* You overlap about 2", yes thin set otherwise it won't stick. Try to find Kerdi Band for the corners it's thinner so to limit buildup. Thin set will not stick to the tub.

Are you using the same tiles on the walls? If so, could cause some problems.

Man you ask a lot of questions in one post. :whistling But I have fond memories of your area since my son went to "the" university just east of you. :thumbsup: so feel free to ask more anytime.

Jaz


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## ApgarNJ (Apr 16, 2006)

So angus, you just cut the kerdi and make a butt joint seam in the field and corners and then run kerdi band (with thinset) over that butt seam with the kerdi band centered over the seam? I thought I remember seeing guys overlapping it in all the schluter videos i watched a while back. 
I have to find a local store that sells kerdi and kerdi band. I gotta start doing the tile later next week.


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## angus242 (Oct 20, 2007)

ApgarNJ said:


> So angus, you just cut the kerdi and make a butt joint seam in the field and corners and then run kerdi band (with thinset) over that butt seam with the kerdi band centered over the seam? I thought I remember seeing guys overlapping it in all the schluter videos i watched a while back.
> I have to find a local store that sells kerdi and kerdi band. I gotta start doing the tile later next week.


You can do it either way. I'm suggesting the Kerdi-Band because you won't get the larger "hump" that you would if you overlapped Kerdi to Kerdi. But as long as you lap by 2" minimum, you're good to go anyway. Here's what I'm working on this week:









You can go either way, Kerdi first and then the Band or like I did, Band and then Kerdi.

Now in my picture you may see a few things different. I don't use CBU or regular gypsum board. I use DensArmor. You will see I did tape some seams but that is only because of the natural tapered edges of the wallboard. I meshed taped and filled the edges that are tapered so as to keep the walls as plumb as possible. You will also see I used Hydro Band on the walls areas that are not getting Kerdi. All of the walls are getting tiled.


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## ApgarNJ (Apr 16, 2006)

Thanks for the replies. I think putting the kerdi band in the corners first seems like the way to go first. Is there anything wrong with using green board everywhere and kerdi over that in the shower. I'll tape the seams and level off the indent where the horizontal seam of the drywall is. I can use mortar for that.

I'll have to see where to buy Kerabond and Keralastic in my area. Most places around here carry TEC thinsets and grouts.

so where the kerdi meets the tub lip, the kerdi doesn't overlap at all onto this area? I'll look into kerdi-fix to find out what it is, and how to install.


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## ApgarNJ (Apr 16, 2006)

what did you tape those seams with, it looks dark like thinset, you used mesh tape with thinset over the densarmor seams?


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## angus242 (Oct 20, 2007)

ApgarNJ said:


> Thanks for the replies. I think putting the kerdi band in the corners first seems like the way to go first. Is there anything wrong with using green board everywhere and kerdi over that in the shower. I'll tape the seams and level off the indent where the horizontal seam of the drywall is. I can use mortar for that.
> 
> I'll have to see where to buy Kerabond and Keralastic in my area. Most places around here carry TEC thinsets and grouts.
> 
> so where the kerdi meets the tub lip, the kerdi doesn't overlap at all onto this area? I'll look into kerdi-fix to find out what it is, and how to install.


You can use whatever wallboard you want. Some like to overkill and use CBU. The reason I use DensArmor is the entire bathroom gets 1 type of wall covering. Even if I weren't tiling all the walls, I would have rocked the same way; just finish differently.

You have the Kerdi overlap the tub flange lip just a bit. Where the Kerdi will attach to the tub, you use Kerdi-Fix to adhere. In the "what do I do here arrow", use Kerdi-Fix.


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## angus242 (Oct 20, 2007)

ApgarNJ said:


> what did you tape those seams with, it looks dark like thinset, you used mesh tape with thinset over the densarmor seams?


Yes, it's alkali-resistant mesh tape with thinset. I use that combo because typical drywall compound likes to emulsify when wet. There's water in the thinset. I'm using rater large tiles on the wall so I want the Kerdi to stay attached to the wall. If you've never seen DensArmor in person, it has a rough, water-resistant textured finish to it. It's a really nice surface to tile to; or in this case, Kerdi to. 

The tape & thinset was not necessary, I just did that to fill the tapered joints.


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## ApgarNJ (Apr 16, 2006)

yeah, I have done entire basements in densarmor so there is no paper down there. better to resist mold.


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## angus242 (Oct 20, 2007)

ApgarNJ said:


> yeah, I have done entire basements in densarmor so there is no paper down there. better to resist mold.


BEST to resist mold. I've never seen mold grow on fiberglass. It's all I will use in a bathroom. Sh!t is itchy as hell to cut/install. :sad:


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## ApgarNJ (Apr 16, 2006)

yeah. we installed over 50 sheets of it, and had to carry it down into a basement a few years ago. wow it was itchy. I got a killer deal on it too.

our local lowes sells it. our HD sucks here.

looks like there is a Mapei dealer down near the job where we are doing this bathroom. funny because the job is 1.5 hour drive to the shore from my house.
and the dealer is almost on the way! 

nothing within 25 miles of my house that sells kerabond


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## superseal (Feb 4, 2009)

angus242 said:


> You can use whatever wallboard you want. Some like to overkill and use CBU. The reason I use DensArmor is the entire bathroom gets 1 type of wall covering. Even if I weren't tiling all the walls, I would have rocked the same way; just finish differently.
> 
> You have the Kerdi overlap the tub flange lip just a bit. Where the Kerdi will attach to the tub, you use Kerdi-Fix to adhere. In the "what do I do here arrow", use Kerdi-Fix.


Off topic; 
Angus, what program do you use for these type drawings. I just tried using paint for a quick drawing and by the time i got done resizing it was awfully blurry. just posted in carpenty if you want to take a look.


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## angus242 (Oct 20, 2007)

superseal said:


> Off topic;
> Angus, what program do you use for these type drawings. I just tried using paint for a quick drawing and by the time i got done resizing it was awfully blurry. just posted in carpenty if you want to take a look.


Actually I just stole that pic from the internet. :jester:

But you could create something very similar and easily with SketchUp


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## ApgarNJ (Apr 16, 2006)

angus, do you buy your schluter products online or in a store? Amazon have ok prices? not sure what is a good price for kerdi and ditra.


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## CCCo. (Jul 19, 2009)

Thanks for this thread, trying to sell my first ditra job right now. 
I appreciate the review, on top of the research I've previously done.

Its always nice to hear it from people who use it, and how those methods work. :thumbsup: 

I've done plenty of tile using old school procedures, but well, it is a new century now. :laughing:


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## angus242 (Oct 20, 2007)

ApgarNJ said:


> yeah. we installed over 50 sheets of it, and had to carry it down into a basement a few years ago. wow it was itchy. I got a killer deal on it too.
> 
> our local lowes sells it. our HD sucks here.
> 
> ...



Lowes stopped carrying it here. Now all that is very convenient is Menards.

Got a Laticrete dealer nearby? You could use 272 + 4237.


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## angus242 (Oct 20, 2007)

ApgarNJ said:


> angus, do you buy your schluter products online or in a store? Amazon have ok prices? not sure what is a good price for kerdi and ditra.


Locally. Some time last year Schluter put the clamps on those large wholesalers selling across state lines. My cost on Ditra went up 30%.


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## Splinter (Apr 5, 2005)

Does the 4" octagon have 1" dots with it? Schluter doesnt recommend anything smaller than 2x2 tile on Ditra... That might be an issue, worth a phone call to Herr Schluter.


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## ApgarNJ (Apr 16, 2006)

angus242 said:


> Lowes stopped carrying it here. Now all that is very convenient is Menards.
> 
> Got a Laticrete dealer nearby? You could use 272 + 4237.


I found a dealer that will help me with his job. for both schluter and mapei products. there is a dealer near me that can get schluter but doesnt' stock it. so next job that comes up closer to me. i'll have to order it ahead of time.

Lowes near me has laticrete thinsets that I have used in the past as well.

I rarely work down at the shore. since I am at the total opposite side of the state. I burned through a whole tank of diesel in two days going to this shore job.


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## angus242 (Oct 20, 2007)

Splinter said:


> Does the 4" octagon have 1" dots with it? Schluter doesnt recommend anything smaller than 2x2 tile on Ditra... That might be an issue, worth a phone call to Herr Schluter.


I would not use Ditra in that case. The 1" dot would scare me away.

Maybe look at NobleSeal CIS? I do think some kind of membrane is better than just going over CBU.


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## ApgarNJ (Apr 16, 2006)

i know you said un-modified to install kerdi over drywall etc, but for the tile to kerdi it's also un-modified?


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## angus242 (Oct 20, 2007)

ApgarNJ said:


> i know you said un-modified to install kerdi over drywall etc, but for the tile to kerdi it's also un-modified?


Yep. Kerdi is always non-modified; both sides. 

Actually, easiest to remember all Schluter stuff is non-modified EXCEPT Ditra over plywood.


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