Thinset under Ditra [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


View Full Version : Thinset under Ditra

irish tileguy in michigan
04-01-2008, 02:17 PM
Just curious to see what the pro's here are using to stick their ditra to the subfloor (plywood subfloor).
Looking for name brands.
At the moment we are using single flex.

Sponsored Links

04-01-2008, 03:06 PM
flexbond and uf2 is what I usually use.

04-01-2008, 03:18 PM
Versa Bond to plywood - Ditra Set to concrete.

04-01-2008, 03:41 PM
Plywood/advan tec Laticrete 254.....ditra set on slab

04-01-2008, 03:57 PM
Versabond Gray.

04-01-2008, 04:13 PM
Laticrete 254 most times, also flexalastic w/ ditra set. Its overkill I imagine I just sleep better knowing its not going to let go. Tried versabond once, set ditra 1st day, tile the next as usual, had to pull a tile, you guessed it the ditra came with it. will not use it again.

04-01-2008, 04:49 PM
Ceramic tile over Ditra over plywood is the plan, and reading at Ditra's site it says to use Modified Thinset between the plywood and the Ditra, and Unmodified Thinset between the ceramic tile and the Ditra. At least that is how I understood their instructions, but I'd appreciate a little confirmation from you guys :) Is this right?


04-01-2008, 04:53 PM
Right on Kathy.....thats the way I tile w/ditra

04-01-2008, 06:07 PM
I don't know what's up, but I'm not impressed at all with ditra. Matter of fact, I avoid using it whenever possible. But I do like it when I have to do repairs. Get an edge, shove something underneath it and you can pull the whole floorup almost like that trick of pulling the table cloth from under the dishes.

Mebbe I'm missing something. Mebbe it's just good marketing. I just can't see how something hard can stick to something soft and flexible. My experience is it can't. This is how I can easily get thinset off of spacers...just a twist.

So why should a different color plastic be any different?

04-01-2008, 06:18 PM
Gary - From my experience - when installed correctly - you are NOT getting tile or thin set off of ditra with just a twist. You may get it off if broken into umpteen pcs or destroyed beyond failure but no way with a twist.

I have torn out some installation - not mine - where ditra was installed incorrectly & you are right in that it comes up nice & easy.

The difference is in "correct" installation to begin with - a spacer is a smooth flat surface - ditra has dove-tailed pockets that act as mechanical fasteners when properly installed. The fleece lining on the under side also acts like a mechanical fastener.....when installed properly.

You prefer cutting concrete board to cutting ditra?

Just your opinion - I know - this is just mine - I love ditra.

Scottish Tile and Stone
04-01-2008, 06:26 PM
When its installed correct. The tiles not going to just come up for ya.. I installed some westminster tile last year. She decided she wanted to inlay glass tiles after the job was set. I had to break out the tile and replace with the new ones.. Lets say it wasnt fun..

04-01-2008, 07:09 PM
Gary the thinset doesn't necessarily just stick to the plastic, it is mainly locked in place by the dovetail design of the holes. Look close at those holes and you'll see that the vertical sides of each hole are not vertical, but widen out. The bottom of each hole is bigger than the top, so it locks the mud in mechanically like a dovetail.
Also the Ditra is not so soft once all the holes are filled and it hardens. It makes many tiny "columns" that are perfectly rigid and bear solidly on the floor below, but between those columns it has tiny bit of flexibility that allows the whole floor to move as one without "pinching" in one spot.
Remember, cement boards are stiff & strong & great... if they had no seams. But they have lots of seams and they are so stiff that they transfer all movement & expansion stresses to the edge, where it is concentrated & can often crack right through the tile if its not installed properly. Ditra, being microscopically flexible everywhere, has no such pinch points to transfer through the tile.
Also, it is an uncoupling membrane. It is supposed to be attached to the subfloor not too much more than necessary, otherwise it would be a defect.
I use it for my most challenging substrates where I need the very best underlayment I can get but can't fit the height of a mud floor. :)

John Bridge
04-01-2008, 08:07 PM
Hi Gary, :)

I think you're a candidate for Schluter training. Look up your local rep and get on the list. It'll change your outlook, I think. Changed mine. ;)

04-01-2008, 08:16 PM
I talked on the phone with a nice lady from Schluter and she even told me I could take the class again if I wanted, in fact she encouraged me to think about taking it again. She is sending me a listing of all the available classes. So, I can guarantee that anyone who is interested in the class could surely get signed up.

04-01-2008, 08:23 PM
The whole idea of ditra as I understand it, is to uncouple the tile from the substrate so that any movement that may occur in the substrate will not be transfered to the tile.
Tec superflex under the ditra

04-01-2008, 08:32 PM
"I just can't see how something hard can stick to something soft and flexible"

Gary, you really got to get out more.


PS, just remembered that we had to take apart a Kerdi install a couple years ago. It was a marble job. Everything was ripped apart, marble included, getting that stuff off. On the walls we went over dry wall and it had to be replaced. No table cloth trick here. Unfortunately I had made a shower bench out of concrete brick and getting the kerdi off of that was a pain!

04-02-2008, 07:03 AM
Mebbe I do need to get out more.

The tear outs, I just stick a floor scraper under an edge, usually where the transition would be, give it a shove and it comes up pretty easily.

I guess the reasons I don't like it is it's home despot orange....ok, that's not it.
It's hard to mark, to keep marked, eats thinset, and adds gobs of not needed elevation. When running heating, IIRC, total elevation was about an inch.

Cutting and laying backerboard is preferable by me because it's easier to cut straight, lays flat, and is eaiser to lay. There's a reason I can't do laminates and carpet. ;)

I can't see any use for ditra other than, like Tom said, for a bad floor that one can't float. If it's over sufficient plywood, why not use Dal Seal? (or a noble product)? Or rough concrete?

I did a bathroom over gypcrete and thought this product would be good for that app. I just used a watered down latricrete primer in 2 coats, then thinset and stone. But then again, what advantaged would ditra offer over dal seal type membranes?

"school"? Only if there are cute girlies...then my GF would probably get mad and ground me...

John Bridge
04-02-2008, 07:28 AM
Actually, Nobleseal TS and Dal-seal are the same product -- made by Noble Company, and it's a fine product. I recommend it just like I recommend Ditra.

But the dialog here seems to center on whether Ditra is good or not. I can assure you it is very good, but there is room here for everybody. You prefer backer board, and that's fine. :)

The fact that Ditra will easily separate from a floor when a scraper is inserted at the edge has absolutely nothing to do with Ditra's effectiveness. Schluter does not intend a strong bond between the mat and the substrate. In fact, the specified shear-bond factor for Ditra attachment is only 50 PSI. You just don't need a strong bond.

I still recommend you sign up for Schluter training. It's an eye-opener. ;)

04-02-2008, 10:44 AM
The bond is right where it's supposed to be, like John said. Think hard for minute on how an uncoupling membrane should work. :shades:
It's biggest application is everywhere you would use backerboard on a horizontal surface: floors, counters, etc., in other words on almost every single job.
Height is not a problem because it performs the functions of a backerboard (better actually) at half the height.
Nobleseal & Dalseal are great products that I do love & use when I need to steal back that extra 1/16" height or for outdoor waterproofing, but for everyday use they are actually more expensive because of the volume that Ditra does as a regular floor underlayment.
Btw, tiling directly to gypcrete is a defect IMHO, even if you can get it to stick, because every one cracks, lots, and it will go right throught the tile.

Tileman Packerfan
04-02-2008, 11:27 AM
Can't agree more about tile over gypcrete. 2 years ago {I think} one of my contractors wanted me to tile over gypcrete directly with it only being sealed. It was a large condo project {just 2 stories} with about 800 sq. ft. of stone in each unit. I told him the only way I'd do it was using ditra. He ended up going with some fly by night installers who fired it in.

Well last year he called me and asked me how much it would cost and how long it would take to replace the stone in every unit. I wanted give him an "I told you so" but I bit my tongue.

Ditra is a great product, I've never had a problem with it, never.

04-02-2008, 06:07 PM
I still recommend you sign up for Schluter training. It's an eye-opener.
I'll give that some thought. I'm pretty loyal to hard rock tools and dislike dal.
Will do the home despot if they have a seminar there and include pop and hot dogs. :D

04-02-2008, 06:16 PM
Btw, tiling directly to gypcrete is a defect IMHO, even if you can get it to stick, because every one cracks, lots, and it will go right throught the tile.
I agree and tell them right up front. Most of these I've done are high end condos, so it's like most...hold a short spell, then sell. They've aged quite nice and look so. Or ugly. I figure the building are about 20+ years old, so it should be thru cracking a lot by now. Sometimes it's hard to talk them into a SLC pour, so I just float out the really bad spots. So, I follow the line...notice I didn't say level line? That's cool w/me if that's what they want...until we set the cabinets, etc. :lol1:

04-03-2008, 06:08 AM
Versabond gray, under. 317 over. :D

I would use Ditraset, but it's not available locally. :cry:

irish tileguy in michigan
04-03-2008, 06:14 AM
i know you were up here for the schluter training, how far away are you in Ohio? , maybe its time for another road trip to get the ditra-set.

04-03-2008, 06:36 AM
Steve, You're probably right.
I can get the ditra-set up around Cleveland, it's only about an extra 50 miles outta my way.
I'm about 290 miles from Detroit. :)

04-03-2008, 07:01 PM
i use versabond over ply then kerabond with water nice mortar to work with and also use it over and under kerdi.

04-09-2008, 01:40 PM
Right on Kathy.....thats the way I tile w/ditra

We're using Dal-tile ceramic tile, for the backsplash which won't have Ditra under it, should we go with the modified thinset on the wall?


tony lamar
04-09-2008, 06:23 PM
I noticed a couple of you mentioned "when installed correctly". I'm just curious what y'all are considering to be incorrect? Do any of you burn in the holes first then lay the next day? Sorry if a little :topicoff:

04-09-2008, 10:39 PM
The correct way is to ensure you have full coverage over the floor and into the fleece. And second to make sure you fill all the cavities before setting tile, which for me, means using the right consistency of thinset and burning it in by going in several directions. I like to hear the thinset "pop" as the air gets pushed out of the cavities. I've both skim coated the ditra the day before or not. I've had no problems with either method.

If done right, getting tile off the floor is real chore. Here's a picture of some tile I replaced a couple of weeks ago. Tile and thinset came up in small pieces, fleece delaminated from plastic, and floor had to be scraped. I've torn out some hardi jobs easier than this.

04-09-2008, 11:07 PM
The correct way is to ensure you have full coverage over the floor and into the fleece.
Juan, it appears to me that the only use for ditra is in an application where you wouldn't think of laying tile/stone. It appears to be an anti-fracture membrane for severe duty.

This is a good application if it allows you do do it. Or IMO, to further isolate the tile/stone from convection of cold from concrete slabs. Other than that, I see no use for it other than good marketing. That's one of the reasons I've asked here about "what's it for?". No one has given me a good enough that I can explain to an owner as to why they should use ditra.

Heck, I have a few rolls of it in my storage and I've yet to use it. On the bright side, I should be able to use it on the cheap wealthy types that have gypcrete condos if I toss it in as a freebie. ;)

Counter tops? Why cheat? why not use 2 layers of plywood and smear/roll it with waterproofing, then tile it? Why the ditra?

When we've been forced to use ditra, we've bonded it with other items than thinset. I asked him about this, mentioning this board and that it should be uncoupled from the floor, breaking away easily as stated here, and he said that "they sell a carpet glue for ditra but unlike HD carpet glue, it costs 4 times as much".

Still looking for a reason for ditra.

...and "felker only wet saw trials" subject instead of "wet saw trials". But that's a side point---yet still related. :D

In the "reference" section, I'd like to see a "rigid vs. dewalt wet saw" comparo. After all, they are the very similar and most of the people I see on job sites have the yellow and black dewalt. So much so, home despot copied it...sort of.

...but I digress.

04-10-2008, 12:05 AM
"what's it for?" Well here it is Gary, you asked fer it: :D
First, the minor application is what we've been talking about: a super-premium uncoupling layer over cementious substrates like concrete & gypcrete.
Second, the main application: it's the best quality manufactured underlayment for tile over wood subfloors & counters. It provides a solid incompressible layer that has microscopic flex (horizontally only) everywhere so the entire tile layer can move together with itself, isolating the tile from the subfloor.
Typical 3x5 stiff sheets of CBU would be great if they came 1 single sheet the size of the whole room. The problem is in their seams, which is always their first point to fail. When you walk across a stiffer sheet of CBU, all the stress from the movement of the floor is transferred to the seam, where it works against the next sheet at one tiny line. Ditra, on the other hand, spreads that stress out evenly and so doesn't have any "pinch points", like stiff CBU seams. It makes for an effectively seamless install because of the way it works.
Some might say though: 'but my CBU stiffens the floor'. This would be wrong thinking for a couple reasons. First it's only a temporary effect as the cementious nature of most CBU's breaks down in strength over time with that kind of movement. Second, all CBU manufacturers, and the TCA, say that you should not rely on CBU for figuring deflection, or strength of the floor. You need to get that solely from your framing & subfloor.
So I hope you can see why "stronger" underlayment is not better, that's the job of the subfloor & framing. "Flexible" is what makes an underlayment better at it's only role: to isolate the tile from the subfloor.
So the short answer, "what's it for?", is so you can sleep easier at night with a better quality job and so you can make more money from a much faster install than CBU. :)

04-10-2008, 06:28 AM
There we go, now I'm getting an answer other than "you neandertal this is NEW!". ;)
I agree w/the solid floor below, so when it's not solid (up/down mvmt) this is where I thought I could use it, but the movement didn't make sense so using it didn't make sense. Now I have a better understanding of it.

I've decided to pick and choose my use for it whereas before I'd just not bother.
Those condos I've done w/gypcrete, I told them I couldn't guarantee my work and they were OK w/that. But my name is still tied into that, so I think jobs like those will have to be a ditra application. Thermal isolation and severe crack membrane too.

04-10-2008, 06:33 AM
mebbe this is my problem.

is this me or is the install juan posted upside down?

04-10-2008, 07:41 AM
One more thing Gary-probably obvious-but often times using it instead of 1/4" CBU makes it possible to have a perfectly flush transition to adjacent hardwood. That's a big selling point with a customer, IMO.

irish tileguy in michigan
04-10-2008, 06:23 PM
the orange ditra is coming back toward you and beyond that the fleece is still attached to the floor (me thinks)

04-11-2008, 06:48 AM
obstacle delusion as I can't figure it out.
Was gonna use ditra on my GFs kitchen floor, but still have a roll of laticrete sheet and primer. While I've only had one cup of coffee this a.m. so far, I'll prolly use that because GF want's some design in it and I can't mark ditra too well. My crayolas break in the divots.

04-11-2008, 07:28 AM
Hi Gary :)

Two suggestions for marking.

1. Use a inkline
2. Prefloat the divits

04-11-2008, 10:14 PM
The picture is right side up. The ditra is rolling forward and the fleece is on the floor towards the back of the picture.

I was pulling up a few tiles cuz I didn't like them and thought about what a pain it was to get down to the subfloor. Then I thought about some of the ditra discussions that we have around here from some of the nay-sayers and my camera just happen to be in the truck. :)

My first experince with Ditra was less than favorable. After replacing some tile from someone elses bad ditra install, I decided to do some more research into it. I learned all I could and tried it, now I'm a solid fan of it. However, I still use other products now and then, it depends on the application and job requirements. But most of the time, Ditra fits the bill.

Gary, I certainly won't say your method is bad or wrong - look at all the methods in the TCNA handbook and find the method that suits you. However, I have tried several of the methods and have felt that Ditra is, for me, faster, simpler, easier, and more cost effective.

My 2 1/2 cents.

04-12-2008, 07:45 AM
Juan, I figured some sort of obstacle delusion because of how the felt was so clean and the lines in the dried thinset. I just wasn't smart enough to figure it out.

The inkline is a good idea (tajima), but I'm mostly a one man show, so I use a wall laser, then mark off sections, then connect them w/a straight edge.

I'm definitely in favor of it and will really push for it over gypcrete.

04-12-2008, 09:32 AM
If you are using a straightedge to connect the dots a sharpie works great. I use a sharpie to mark on the ditra. Although, I guess you might have a tough time seeing the laser on the ditra huh? We need a blue laser for ditra.

Been thinking of getting a laser, which do you have and do y0u like it?

04-12-2008, 11:13 AM
Steve - Over in the UK, for fitting Ditra to plywood base it was established pretty early on to use a carpet / heavy vinyl covering type adhesive. I use Ardex AF200, there is also a Mapei type and others.
I see that in the US its always a mortar adhesive used, wonder why? The advantage with an acrylic type is that it is straight out of the tub, spreads very quickly (yes v sticky if not controlled - but then we're pros right) and there is no down time for getting on it, no additional height from half a millimetre of bed, and no worry about sheet slip etc. I prefer to leave it overnight before fixing the tile because it can pull up if there is enough suction from the large tiles if done on the same day. By the next day though it is really down. Are there any moves to use this type over there? Im assuming 'Ditra Set' is a mortar ads.
I also push to use it over screed substrates also - it overcomes all the problems that used to be associated with floors.

04-12-2008, 07:33 PM
I did the ditra thing on a kitchen floor today. I used the sharpie and yes, the laser can suck on ditra, but if you come facing it it's better. I've used the end of a margin trowel when it got too bad.

I used the torpedo laser to square up a room, but that's bitten the dust. The one I use now and have gotten the most use out of is:

Great for showers, etc. This is another "dewalt thingie" I turned my buds on to.
When ya set it down and shoot a vertical, it goes out front...then up and behind you a ways. Slick. I've used it for framing a lot too (a la the rotating laser for say, hanging suspended ceilings). I got one when the first came out, but now they're less expensive...and well worth it. We pretty much stopped using levels.

Set it on horizontal, put it down and w/a tape, you can check the floor of a wide, big room.

How soon before target puts out one? :lol1:

04-12-2008, 07:39 PM
Steve - Over in the UK, for fitting Ditra to plywood base it was established pretty early on to use a carpet / heavy vinyl covering type adhesive. I use Ardex AF200, there is also a Mapei type and others.
not much better than carpet glue.
I see that in the US its always a mortar adhesive used, wonder why? The advantage with an acrylic type is that it is straight out of the tub, spreads very quickly (yes v sticky if not controlled - but then we're pros right)
Colin, here in the US, we highly value the hair on our forearms (and heads if you're really creative).
Also, no one will admit to using one of those cheap, throw away v notch trowels.

Are there any moves to use this type over there?
There is "some", but we tend to keep it amongst us non "FULL TIME TILEMEN" :D

04-13-2008, 06:13 AM
Carpet glue should only be used to install carpet. It is designed to break down as it gets older so that the carpet is easier to remove when it is time to replace, carpet does not last as long as tile. The glues in the uk may be diferent but here that is what carpet adhesives are supposed to do.

Tile Machine
04-14-2008, 03:43 AM
I use laticrete 317mixed with 333. Nice bond