Photo 1
I am not writing this to tell you why your tile is cracking or why your grout is cracking – I have other posts that may tell you that. (Click on the pretty little links 
) If you happen to have Schluter Ditra as your substrate, this post will tell you why either one of the above may be happening.
While Ditra is my preferred membrane for floor tile installation (as well as countertops and tub decks) it absolutely needs to be installed correctly. The two main techniques for this are fairly simple:
- Make sure the cavities (waffles) are filled correctly
- Install it over an approved substrate (and with the correct type of thinset mortar)
Photo 2
There is a lot more to ditra than those two items but if either one is incorrect I can nearly guarantee a failure. See photos 1 and 2 there? The tile was cracked and it was a direct result of a) not getting the waffles filled correctly and b) improper coverage on the tile. Now b may be due to not backbuttering the tile, an improperly-sized trowel, letting the thinset skim over or set too long before installing the tile or simply incorrectly mixing the thinset. All three of those things will cause any tile installation to fail – whether you use ditra or not.
Not filling the waffles correctly, though, will cause the tile to not be fully supported and/or not ‘locking’ the tile into the ditra. Because it is not correctly locked into the ditra you will lose the mechanical bonding properties of ditra and you may as well install it directly to particle board at that point (That was sarcasm – don’t do that!). For more specifics about exactly how ditra works you can check out Provaflex vs. Ditra wherein I describe exactly how the mechanical bonding process works – and rant about a particular jackass. But the mechanical thing – that’s what you want to concentrate on.
You need to use the flat side of your trowel and spread thinset in every direction over the ditra to ensure that all the little waffles are full. Since the cavities are dovetailed (that means they go down and away from the opening) you need to ‘force’ thinset into the bottom corners of the cavities. Simply running the trowel over the ditra will not do this. Simply running the trowel over the ditra did that (photos 1 and 2).
Photo 3
Installing ditra over an approved substrate is much, much easier. In fact, nearly every bare substrate you find in a modern house would be considered an approved substrate – shiny linoleum is not one of them (Photo 3). While there are thinsets that ‘say’ they will bond to linoleum (and some of them will) apparently the jackass who installed that particular floor was not aware of that. 
See photo 4? I lifted that up with my pinkie – literally! It was not attached at all. He may have had correct coverage beneath the tile and all the little waffles filled – I have no idea. There was not enough stuck to get enough leverage to tear one off and find out.
Photo 4
Most any plywood (even osb 
) is an approved substrate for ditra. And if you use a thinset approved for that substrate, there are no problems at all. Photos 3 and 4 had an unapproved substrate and, apparently, incorrect thinset (and a shitty tile job, but that’s a whole other post). It was nearly guaranteed to fail.
When you buy ditra for your installation every roll comes with a handy little instruction booklet. You can go to Schluter’s Ditra Page on their website and access the instruction booklet (This link is a PDF!). They even have a flash video about the proper installation technique. You can leave a comment below and ask. You can email me. You can send up smoke signals – I’ll answer.
Given the 17 ways to acquire correct ditra installation information above there is absolutely never a reason to do it incorrectly. Ditra, in my opinion, is the best membrane for most floor tile installations. The only time I’ve seen it fail is due to incorrect installation. And that isn’t just the common BS everyone accuses failures on. Me, personally, every one I’ve seen fail is incorrectly installed.
If you use ditra, and if you have an approved substrate, and if you have the correct thinset mortar, and if you fill the waffles correctly, and if you use the proper trowel and get proper coverage it will not fail. Yes, that’s a lot of ifs – when you read it. In practice it really is not that many things to get right. It’s just common sense, mostly.
So here’s one more if: If you have any questions at all about correctly installing ditra and using it for your tile installation please, for the love of all the marble in the Sistine Chapel, ask me below in the comments. I WILL answer you. I’m just super-cool like that 
Common Mistakes and Fixes
Improper substrate
Proper substrates consist of tile or wood. That’s essentially it. Specific types of wood vary, but your substrate should be one or the other – BARE, with nothing installed over it. The images above depict Ditra installed over linoleum. If your thinset will not bond to the surface you are installing over it will fail – every time. If you are unsure whether you can effectively install over something, just ask. I answer all questions.
NOT fully embedding the ditra fleece into the thinset
Spreading thinset and simply laying the Ditra on top does not constitute ‘installing’ it. The fleece on the underside of the Ditra needs to be fully embedded into the thinset. This means that thinset will encapsulate each thread of the fleece and surround it, thus locking it into the cured layer.
Once you lay it down you need to use a flat…something, to push the ditra down into the thinset. I use a concrete float or a straight-edge. You can use your (clean) trowel, a float, even a flat 2/4. Anything to press the ditra into the thinset layer.
You can see whether this is happening after you get it installed. IF it is properly embedded you can see it through the plastic from the top, those areas will appear darker (the thinset is directly against the backside of the plastic, which means the fleece is embedded).
While I don’t recommend it, you CAN use white thinset to install the Ditra, you can still see the color change in the embedded areas, it just isn’t as pronounced. Gray is always better for installing Ditra to the substrate.
Improper type of thinset used for the type of substrate
When installing Ditra you should use UNMODIFIED thinset when installing over concrete, and MODIFIED thinset when installing over a wooden substrate. With this most failures are a result of using unmodified thinset to install ditra over a wooden substrate. That will eventually fail 90% of the time.
Not properly filling the cavities when installing tile
The mechanical aspect of Ditra relies on the dovetailed cavities in the top being completely filled beneath the tile. If they are not, you do not get the full support needed, nor the proper bond to the membrane, which can lead to failure.
Fill the membrane with thinset using the back (flat) side of your trowel, spreading in every direction, THEN comb the thinset out in those pretty little lines for your tile. Properly filled cavities is the only way Ditra works.
Frequently Asked Questions
What type of thinset do I use when installing Ditra to my substrate?
When installing over a wooden substrate use modified thinset. When installing over a concrete substrate use unmodified thinset.
Can I use modified thinset to install tile to Ditra?
In reality? Yes, you can. No, it isn’t necessary. Yes, it will void any warranty. And yes, you likely have access to unmodified thinsets, even if you don’t realize it. Bonus: It’s normally cheaper than modified thinsets.
Can I fill the cavities flat then come back later to install the tile over it?
Yes, you can, with a few caveats:
Do not fill it, wait a week while treating it as a regular floor you can walk all over, then decide to install tile over it. If left untouched (unwalked) you can wait a week. But it’s always better to fill it, then tile over it the next day or two. Filled Ditra IS NOT a ‘wear layer’, meaning that once cured it is not designed to endure regular foot traffic. It’s still an ‘in process’ layer, not a temporary placeholder until you FINALLY decide which tile you want.
If you fill the cavities, try using your grout float. It works much better and takes off the paper-thin layer which will sit on top after you fill it with your regular trowel, then crumble into a dusty mess when you look at it the next day. The float keeps most of the thinset just below the surface, in the cavities where it belongs.
Hi …
A new question for you…. well new from me anyway…
We had to rip out everything due to water damage. We put in new tongue and groove 2×6 board since that’s what was there to begin with.
My question is do I put plywood back down first or just the 1/2 inch cement board?
after that I plan on putting in suntouch floor mat then Ditra? then the Tile.
do you recomend the Ditra too or is that getting carried away?
Its a small space (5×8) but I want it to be right from the begining. I dont want to have to redo it!
Thank you,
Michelle
Hi Michelle,
For what you have there you can install plywood, then your heating, then ditra, then tile. If you want the backerboard between the plywood and heating that’s fine, but not really needed. The ditra would be a better choice than backer, if given the choice.
Really need a pro opinion on this….
Found a nearly 2 inch thick mortar bed cracked to hell under my 12×12 kitchen floor and although after research I now believe it would have been much better to just pull the whole thing up and start anew, I came home to the installer pouring a new section where it was formerly tetoring under the prior laid kitchen carpet and he filled in all the cracks with vinyl concrete and then filled by levelor. Now under time constraints it being thusrday and tile installer coming in to set tile Friday eve/ Saturday. I wonder if it would be wise to go ahead and put use ditra over the top of this old cracked but patched mortar bed. Hoping it would decrease the chance of tile cracking etc if the tiles are just laid directly on the patched up mortar bed. Also what do you think of using flex bond thin set in this case and or tile leveling clips wedges. Thanks so much for a quick response
Hi Gordon,
Not too sure what you mean when you say ‘vinyl concrete’ – not sure what that is.
It would be best to use either ditra or flexbond. Either will compensate for in-plane movement, flexbond will compensate for a SMALL bit of vertical movement as well. The tile leveling clips (L.A.S.H.) would be fine, but really don’t have anything to do with the amount of movement. They will also NOT compensate for an un-flat subststrate. They simply level the tile with the adjacent tile – they are not intended to make up for improper or compromised substrates.
Hi Roger,
I’m so happy I found your website! I messed up on my ditra install and I need you to tell me if I need to rip it up. ugh.
Reading the instructions I saw that it requires unmodified thinset to set the tile to the ditra. I read this then happily plowed ahead, using the unmodified thinset to attach the ditra to my plywood subfloor. oops. The subfloor did have a layer of ‘bonderizer” on it, not sure it that might save me….
The area is 5 x 5 ft. Not too big. I plan on putting 1 x 1 marble tile over it.
So, how bad is this? Should I start over? I did this a few hours ago and it seem to be curing ok.
Would appreciate any information you can provide me!
Hi Megan,
It really should have modified thinset beneath it. That said, unmodified will bond it just fine – really. The bigger problem is that the minimum recommended tile size over ditra is 2×2. You can install the 1×1, but it may be problematic. Just make absolutely sure you get full coverage beneath your tiles and you get the waffles completely filled.
Thank you! I didn’t realize the 1 x 1 sheets could be a problem. ~sigh~ It’s always something! I will make sure to get the full coverage.
I just thought of another question: regarding grout: Since this is polished marble with 1/8″ grout lines I was planning on using unsanded. However, I just read your post about the epoxy and the Spectalock. Sounds like something I’d like to use since I want to go with a lighter color and could use the stain resistance. I followed your link to the laticrete product info and they say that the grout contains sand and “may scratch soft or polished marbles.” What’s your opinion?
Thanks again!
Megan
My opinion? I just installed Spectralock in a $24,000 (yes, you read that correctly) bathroom with white thassos marble. I think it’ll be just fine.
Hi Roger, I’ve just ripped up an old ceramic tile floor in my dining room. The subfloor consisted of plywood (5/16 thick) then what looks like mortar with wire lathe in it and finally the ceramic tile. My question is should I just put the DITRA directly on the plywood or can I use a cement board over the plywood and then use the DITRA on top of the cement board.
Thanks,
Anthony
Sorry Roger, The plywood subfloor is 5/8 not 5/16 thick.
Thanks,
Anthony.
Oh, in that case you need another layer of 1/2″.
Hey Anthony,
You need another layer of plywood over that. The best option would be to just add an additional layer of plywood over the current ply then install the ditra right over that.
Thanks for getting back to me so soon Roger. So when I add the 1/2″ plywood on top of the existing 5/8″ sub floor do I need to put an adhesive between the two or just screw the 1/2″ directly on top of the 5/8″?
Thanks,
Anthony.
Nope, just screw the second layer to the first. Avoid screwing the second layer into the joists – only into the first layer of plywood. (Not a dire point – your dog won’t burst into flames – just the proper method)
Hi Roger, thanks for that advise,the dining room looks great, too great.
Now my wife wants to do the entry way of the house leading all the way up to the kitchen (about 500 sf and not using DITRA). The subfloor is 5/8″ plywood, After I rip up the existing tile can I just lay cement board on top of the plywood ? If so, what kind of thinset do I use between the plywood and cement board ? I’m laying a natural stone tile and not ceramic. Can I use the same thinset that I used for installing the ceramic in my dining room ?
Thanks,
Anthony
Hi Anthony,
With any type of natural stone you absolutely need a double-layer of plywood at a minimum thickness of 1 1/8″ – so you need an additional 1/2″ of plywood over that. After you install that you can install cement board over it for your stone.
You can use any kind of thinset beneath the backer – it’s only there to fill voids once it cures, not to bond to anything. I don’t know if you can use the same – which one did you use for your ceramic?
Hi Roger,
Thanks a million for the advise. Just wanted to ask you, if my wife decides to change her mind and go with ceramic instead of natural stone, do I still need a thickness of 1 1/8″ or can I just get away with cement board over the 5/8″ plywood ?
Thanks, Anthony
You should still have a double-layer with that thickness – but it isn’t required.
Hi Roger,
I just removed some old tile from a bathroom and I’m planning on using Ditra to lay the new tile. There was some water damage around the toilet (the cause has been addressed) so I cut out a 3’X2′ section of plywood and replaced it with a new piece. The thickness seemed to be 3/4″, so that is what I replaced it with, but I am now realizing that the old piece is just a bit shy of 3/4″. So now i have a small variation (probably 1/16-1/8″) in height between the old floor and the new floor. I am wondering if this needs to be corrected before laying the Ditra. A guy at Home Depot told me that I can correct that small variation by feathering the thinset at the joint and to just be sure to overlap the tile over the joint. However, he didn’t seem to be all that knowledgeable about Ditra, so I’m looking for a second opinion! I’d appreciate your thoughts. Also, the old floor still has some adhesive on it which makes it just a bit bumpy. Will the Ditra be okay over this? Thanks!
Hi Brett,
You can compensate for that height difference with the thinset beneath the ditra. When you install the ditra just use a straight edge to flatten that area and let it cure. The next day it’ll be solid and flat.
By ‘adhesive’ do you mean glue or thinset? If thinset yes, it’ll be fine. If glue it may be a bond-breaker, which means thinset won’t adhere to it and it will need to come off. If it’s shiny it needs to go.
Hi Roger,
Thanks for the quick response! I’m not sure what the adhesive is exactly…it looks like glue in a grid pattern with some brown paper stuck to it, possibly a backing from the old tile? Since it’s just in a grid pattern, would it be enough for the thinset to adhere to the areas inside the grid, or do you suggest removing it all (or replacing the plywood)?
As far as correcting the height difference with thinset, do you mean to put an extra layer of thinset in the lower area, let it dry, and then install the Ditra with additional thinset? I’m a little worried about controlling the thickness of the thinset with a straight edge…would a notched trowel work?
I was also thinking maybe I could just sand the higher area with a gritty sandpaper to get rid of a bit of height and then use a thinner layer of thinset on it to compensate for the rest. I measured it last night and it is really just a bit more than 1/16″ difference…maybe 3/32. Thoughts?
You either need to remove that or replace the plywood. You want a full bond beneath your ditra.
I don’t mean flatten out the thinset itself with your straight edge, I mean add a bit extra thinset beneath that area with your notched trowel, roll the ditra over it, then flatten the ditra with a straight edge. If you sand the higher area around it you’ll still have an un-flat floor, it’ll just be further out.
Hi again,
what kind of caulk or silicone should I use and can I use the same kind in the tub as I use around the edges of the surround? ( I know I want it to be paintable so that the paint doesn’t beed up ) and you use it next to the tub but do you use it all around the edges of the room too?
Thank you so much for your time and also for getting back to me so amazingly fast!
Michelle
Hi Michelle,
I use silicone everywhere, and it is not paintable. Install the silicone after you paint – leaves a cleaner edge anyway. I prefer laticrets latasil.
Hi Roger,
Great post on Ditra. My contractor told me about it and have heard good things. I’ve posted a few times before but I have couple of new questions as I wind down on my kitchen floor install. I’ve read a substantial amount of comments/ replies, but I apologize if some of these things have been answered already.
1. I am using a Schluter RENO-U transition for where my tile meets the wood floor. My main concern is that the wood height varies somewhat (old house, floors have been refinished several times) and don’t want the wood-facing portion of the transition to start at a higher point than the wood (kind of like stubbing your toe on metal). I hope that makes sense. Wondering if you have any other solutions. Once I lay the ditra and set the transition I will have a better idea of how much this will be a problem.
(Assuming I use it)
1a. Should I put the RENO-U right against the wood or leave space in between?
1b. Should I fill the space between the tile and the RENO-U with grout or caulk?
2. When laying the Ditra, does it matter at all how the pieces are laid? I’m guessing fewer seams = better. I have cabinets to tile around so it is a bit tricky with the areas for the range, dishwasher, frige, etc.
3. FINALLY, the most pertinent question. One topic you haven’t seem to have covered yet is how to plan/ layout your tile (unless I missed it!). Like I said, I have cabinets to tile around so I have a couple different approaches I am considering. I have read that you start in the center and work outward so the cut pieces are even at the edges. With the cabinets and such, I could also start with full tiles at the entry way and finish with the cuts at the cabinets.
Here’s a picture if it helps. You can see I just primed my OSB floor
…
http://www.nicholascreative.com/images/kitchen.jpg
Thanks again for this awesome resource! It has made tile one thing I have enjoyed learning about in my home improvement projects. (Drywall is not among those things). Hopefully your answers are easier read than my questions.
Hey Nick,
1. I would likely go with the Schluter®-RENO-TK rather than the U. It has a lip which you can overlap the wood with and you should be able to keep it consistent whether the wood is level or not. Always leave a space (with the U) and always use silicone or caulk.
2. Doesn’t matter at all, seams don’t make any difference either.
3. I would start with a full tile at the entry and have the cut tiles around the cabinets. Full tiles always look better in the doorways.
Thanks for the concise response. I can’t find the TK locally anywhere and I’m still not sure it would work. The Ditra and would floor would be even, so that leaves the tile about 1/4″ above the wood. Do you have any other products/ suggestions that I might be able to find at a HD or Lowes? I really want to make sure the tile edge is protected.
Can you get the Schluter®-RENO-T? If not you may be better off with the U with a gap and silicone.
Hi Roger,
Im redoing my front bathroom because the people who sold me this house installed the toilet wrong and it been leaking under the floor for years. One of my brother-in-laws replaced the floor for me and another is helping me with the plumbing (since everything is torn out I might as well make like I want it). My questions are .. on the floor after the cement board do you need the Ditra too? On a different post from you you didn’t mention using it.
And in the shower you use the cement board then the redguard.
Do you use or need a barrier/redguard on the floor?
I’ve asked so many people… I’ve been to Home Depot so many times to ask them questions but I seem to know more then they do, and thats not much.
When doing the grout some sites talk about curing it … whats that? Then after everything sealing it.?
also you do the grout all the way to the corners on the floor but caulk by the tub? or caulk on top of the grout by the tub?
and the tile in the shower … you leave a gap on the bottom? you put caulk there too right?
and around the outer edges of the tile, the edges of the trim pieces… do you caulk there? how do you make it look nice? the old surround that was in there had caulking around it and when we painted the bathroom it wouldnt paint in some spots, it just beeded up.
I’m not even sure if thats all but I’ll stop for now… I like to do things the right way and cant sleep at night because I keep planning it in my head… Sorry
I love you take on things! Help Me! Michelle
Hi Michelle,
You don’t need the ditra, it’s just an extra layer of protection to compensate for normal in-plane movement. You can tile directly to the cement board.
Cement board with redgard is one way to waterproof a shower.
On the shower floor yes, you need a waterproof barrier. On the bathroom floor you do not.
Curing grout it just waiting for it to dry. Grout drying is curing.
Any change of plane such as corners and all the areas you’ve mentioned get only silicone or caulk, no grout. Leave about a 1/16″ gap for the silicone in the corners and where the tile meets the tub.
Making caulk or silicone look nice is simply practice. Just take your time with it.
Roger,
Good info on the site! I’m putting down a tile floor in a 6 year old floating slab basement. Using Ditra and porcelin tile. I was planning on using Ditraset between the Ditra and the concrete but this stuff is next to impossible to find. What’s a good alternative that is readily available? Is the versabond from HD ok to use between the Ditra and the tile?
Hi Corey,
Not if you’re concerned about your warranty from Schluter. It needs to be unmodified. Laticrete 317 isn’t necessarily readily available but you should be able to order it through a local tile shop. If you aren’t concerned about the warranty then yes, versabond will work just fine.
Roger,
In this case, I’m not as worried about warranty as I am making sure I’m using product that will do the job right and will last the test of time. I’m the homeowner in this case and I’m doing the job myself so the cost of the materials is what I’d be out if I had to replace shoddy worksmanship. So really, I’ve just been trying to unravel all the information I’ve gotten from many resources regarding what is the best stuff to use that will last. So assuming I use the laticrete 317 (I was able to find a local tile shop that carries it thankfully) below the Ditra, it sounds like I could use the Versabond or the 317 between the Ditra and the tile, correct?
Lastly, I’m assuming that I need to scarify the concrete before laying my Ditra, right? The slab doesn’t have any protective coatings on it, but between finishing sheetrock, painting, etc., the surface (despite being scraped) isn’t clean. If I choose to prep the surface, is a mechanical or chemical scarification method preffered?
Hey Corey,
Yes, versabond beneath and 317 above the ditra. Mechanical scarifying is normally best, just have your shop-vac handy. All that stuff should come off the concrete before you install the ditra.
Roger, hi, we are putting ditra on top of 2 layers of osb. In the bathroom and in the laundry room.
I read in one of your posts that you recommend putting a coat of kilz on the osb before putting your adhesive down for your ditra. Did I understand correctly? Also the mortor we are using is Ultra Flex 2 mortor with polymer. Is this the right mortar? Thank you for your help.
Hi Glenda,
Yes, if you put a primer on the osb the thinset will get good adhesion. Ultraflex II is the right stuff, very good thinset.
Hi Rodger. Was wondering if putting Down Ditra the night before the tile is ok? Want to be fresh and ready for the tile work. Thanks.
Hey Jeff,
Yup, I do it all the time. You can fill the waffles with thinset the night before too, it gives you a nice flat substrate when you’re ready to start setting tile.
Hi Roger,
Just forget about my questions 2&3 ( i wish there was an EDIT ability to my previous post)
Question 2 will still be tricky for me as as Schluter has the Schluter-DILEX-EDP system for commercial grade movement joints, but the problem is their specifications are for installations not to exceed 400 sq/ft. So I guess I will have to talk to a rep on what to do.
and that makes me nervous.
Question 3 I already found the answer for.
But questions 1 & 4 are still relevant. Schluter seemed to have no problems with 3/4 inch OSB over 16 O.C. joists, but again, you had the
The control joint issue is the scariest one for me as it is 1800 sq/ft. During my 12 years I never had to be the one to decide where the controls would be because they were already incorporated into the print by the architect, all I had to do was follow the print and make sure I followed the print religiously. But now I am the one to decide where the control joints will go and I am worried!
Hello Roger,
Thank you for your Q & A site. I am a 12 year setter going on my own after my Union dried up. I have no experience with Ditra. It looks like I can ask you.
I have an 1800 sq/ft commercial install coming up. Its an old building with a basement. We took all 80 years worth of flooring layers off (5 nasty ones) and then tuned up all the joists structurally. The we put down 3/4 inch OSB tongue and groove sub-floor on the whole thing. This is going to be a deli/grocery when all said and done.
The Ditra system looks very appealing indeed, but here are my questions:
next to the OSB usage and of course that was not lost on me. So what am I facing with the OSB that is not good?
1) When doing lay-out, do chalking out a grid, do the chalk lines stay, at least long enough to get some clear spray-paint line saver on them?
2) Will I still have to do a control joint every 10 sq/ft for future crack relief, or will the uncoupling properties of the Ditra soak up that movement anyway?
3) In the Ditra guide it says that a modified thin-set is used between the OSB and the Ditra (fine), but then it says to use an unmodified thin-set between the Ditra and the tile. Why? I mean that is great as unmodified is very cost effective, but why would they go out of their way to say “unmodified”?
4) Up above when you mentioned that Ditra is fine over plywood you put a little
Thank you so much.
Hey Jim,
The chalk will stay on there plenty long enough to spray them. Alternatively I use an ink line rather than a chalk line. You don’t need to spray it and it gives you a finer line to work with.
You do still have to leave soft joints every 20 – 25 feet for interior installation. That is, of course, in each direction. The ditra will not take place of those – they still need to be there.
The modified – unmodified argument is one of the biggest problems with ditra. Schluter really, really needs to change that (and already have in European nations). Their initial reasoning being that the modified polymers, which require air to cure, will not do so in the bottom of the dovetail cavities. Unmodified thinset does not require air to cure – it’s all done through hydration. Makes sense, but it’s nearly impossible to find a good unmodified which is readily available. The crap they sell at HD is little more than mud and honestly isn’t worth a shit. I use modified a lot, or I use Laticrete 317. In that application I would order the 317, it’s a good unmodified.
The reason for the tongue-in-cheek comment about osb is two-fold. A lot of osb has a wax coating, thinset will NOT bond to it long-term, if at all. The second, and most pertinent, is the fact that there is not one manufacturer which will warranty their thinsets when bonded to osb – they just won’t. Schluter says it’s okay as long as you use a thinset approved for installation over osb – there isn’t one. Covering their asses and leaving people hanging (they are really, really good at that). I absolutely love Schluter products and absolutely cannot stand the company or their business practices. It’s frankly total bullshit as far as I’m concerned. You can’t even get a straight answer from the company because they do not allow their reps to post or answer anything on the internet – anywhere – in 2012. It’s horseshit.
I think going over the osb like you have there you would be much, much better off coating the floor with a good primer, even killz, then just using your modified of choice. It’ll cover your ass because it will last – DO NOT expect any kind of warranty coverage from Schluter with that set up, but it will work well.
im doing my entry way i used hardy board but a few of the center tiles wooble slightly will the thinset fix this
Hi Pat,
As long as it’s not excessive thinset will compensate for it.
Hello Roger;
I just did a bit of reading about the ditra stuff. Watched their video of an instal, too. This after reading how much you value it … looks pretty cool.
I’ll be tiling my kitchen and after flattening the floor with a final coat of SLC I was planning to put down the hardi backer board. The subfloor is diagonal lumber and 3/4 plywood (then the patching and SLC).
Big learning curve here, so I may have this wrong, but is the ditra something you would use instead of eh hardi backer board?
Even if you already had all the backer board nicely stacked up and ready to go?
Michael
Hey Michael,
I would use the ditra, especially since you have the slc there. Screwing through slc will often crack it, that creates problems and may create voids. The ditra goes down with just thinset – as long as you have a solid substrate you’d be good with it.
Hi Roger, love the website! My husband and I are renovating an early 1900’s brick house–this is our first reno and we’re learning a LOT. We’re currently working on an upstairs bathroom. We’ve repaired some floor joists but still have quite a dip in the center of the floor. The floor feels sturdy–no squeaks or shifting–it’s just not flat. The plan is to build up the center with plywood then flare out the edges with self leveler to create a smooth, flat subfloor. (when we tore out the old floor, it had two layers of plywood and gobs of self-leveler). Two layers of plywood would be necessary regardless of whether or not the floor was flat just because of the height difference at the threshold to the hardwood floor in the hallway. I had resigned myself to having to use vinyl or linoleum flooring until I started reading your blog and learning about Ditra. I noticed while reading the installation instructions on the Schluter website, that they say to install Ditra over ONE layer of substrate. So, I’m wondering now if having the multiple layers of subfloor will cause a problem for the Ditra installation and ultimately the tile floor. I don’t see how it would, but being new to all this, I’m being particular about instructions that come with the products and materials we buy/use. Any advice? Thank you!
Hi Amanda,
Having two layers (which is proper, despite what schluter says ‘may’ be done) is not going to negatively affect your tile at all. It will simply make your floor stronger.
Planning to install tile this weekend in my kitchen. Old 1920’s home.
Planked hardwood subfloor. surprisingly even/level throughout the kitchen! and not a wobble to be had. ( They had 3 layers of ceramic tile and 1/4″ plywood on top of it!)
Put down 1/2″ OSB overtop the subfloor. (Tile place said Ditra with OSB is no troubles , their documentation on the DITRA site supported it so thats what we did ).
It’s secured and solid now.
My question is relating to mortar , The tile place provided us with the DITRA , and the Thin-Set Mortar. TRIO SERVOFLEX GREY THINSET
and said the mortar is used both under the DITRA and on top for the tile.
Is this the right stuff for both under and on top of the Ditra?
Hi Blair,
Congratulations! You seemed to find the one tile store salesperson who knows what the hell they’re talking about.
Yes, that thinset is actually a perfect blend for ditra, I wish I had a supplier for it around here – I’d use it every day. You’ll be fine with that.
Hey Roger,
I’m in the process of remodeling the master bath, and my wife asked why I wasn’t running the ditra under the tub before I install it. I had to admit, not a bad idea. But is it necessary? And if not, what do I use to seal between the ditra and tub.
Great website, check it often for reference. Thanks.
Hank
Hi Hank,
I don’t know, why aren’t you?
Ditra is for tile installation, not a construction sub-panel. It should only be placed beneath your tile, not used to support any other appliances or fixtures without a tile covering over it. Use silicone to seal between the tub and ditra.
Hey Roger,
I’m about to embark on my first tile project and I’m reading over the Ditra Installation Handbook to make sure I do this right but just want to double check I have my terminology correct. I took up my linoleum in my 1950s house and found VAT. Instead of worrying about asbestos abatement, I’d like to use Ditra – which will also be thinest option and provide for a better (lower) transition/threshold between my existing 3/4″ hardwoods in the hallway.
According to the handbook they recommend “fast setting latex portland cement.” I looked at Laticrete 253 Rapid which is fast setting but it appears to be polymer based. In one of your previous posts you mentioned that, despite being polymer based, 253 uses a different plolymer which still relies on the moisture in the thinset to cure instead of air. So maybe that might be best? Multipurpose R looks like it’s portland but I don’t think it’s modified (latex-based?).
After getting the Ditra down unmodified thinset provides for the mechanical bond between the Ditra and tile. Should Megabond with water suffice or would you recommend a better alternative?
Also, in another bathroom my substrate will be 1/2″ CDX over structural planks which requires, apparently, regular-setting latex portland. Should the same Megabond in addition to the Additive make the thinset modified (latex-based?)?
Don’t want to be the victim of one of the above bullocks-struck installations by starting off my project with the wrong materials.
Thanks!
TJ
Hey TJ,
The 253R would be your best option over that VAT. Dunno much about the multipurpose R – that’s the retail consumer version of one of their thinsets and I don’t know which. I do know the 253R will work great, though.
The megabond with water will be a fine thinset for over the ditra. And mixing it with the additive will also make it suitable (modified) for your other bathroom. Sounds like you’re on the right track.
We are installing ceramic tile on a bathroom floor. We have taken up the 6″ x 6″ tiles from 1937 and some black adhesive remains on the plywood. Can Ditra be installed over this? How can I get the adhesive up?
Hi Mary,
If you can’t get it all scraped up (that’s about the only way to get that stuff off) you can install the ditra right over it provided it’s all nice and solid. And if you can’t scrape it up – it’s all nice and solid.
The guy at the tile store told me Ditra over glued vinyl is redundant, that as long as the vinyl is field-glued and not just along the parameter, that they make several product that bond tile directly to vinyl. The vinyl is from the early 70’s over what looks like 1/2″ particleboard over 3/4 hardwood. He also told me it’s very likely Asbestos and as long as it’s structurally sound not to pull it up, maybe screw down through the joices and tile directly over the vinyl after cleaning it. You’re take?
Hey Fred,
To be quite blunt my take is that the guy at the tile store is full of shit.
1. There is absolutely NOTHING redundant in regards to a comparison of ditra and glued vinyl – NOTHING.
2. Particle board has absolutely no business anywhere near a tile installation – ever.
3. While there are products that will bond tile to vinyl there is not one product on the market that will guarantee the bond of the vinyl to the underlying substrate is durable enough to withstand a tile installation – screwed into the joists or not.
You NEED a proper substrate to bond the tile to. The particle board really, really should be removed. While the vinyl may or may not have asbestos – it is still installed over an improper substrate. At the very least you should install cement backerboard over the vinyl with thinset installed beneath it and screw the hell out of it. This would be a much better option than attempting to install directly to the vinyl.
Hey Roger, I installed 1/2 plywood over 2×6 t&g for strength (after adding additional floor joists). I have two questions: 1.) The plywood is for sheathing and is rated “CD”, is that an issue? 2.) Can I install a suntouch heating matt to the plywood before the Ditra? I have height issues and preft not to install backer board over the plywood if possible. P.s. Love the shower pan download
Hey Sheldon,
By TCA standards your plywood should be a minimum of ‘AB’, but CD is used often. Not ideal, but it will work. You can install the heating to the plywood then the ditra, no need for backerboard.
hi roger,
ive torn up a bathroom floor that was laid over ditra, ive got the ditra up aswell.
do i need to remove the mortar thats stuck to the floor? or can i just mortar over it to put down new ditra.
Hey Cam,
Ideally you want to get it all off, but I know that isn’t always possible. Just get as much as you can off and go over it with new ditra.
Hi Roger, when tiling a bathtub surround, how do you start the first course of tile. I am using 3×6 subway tile, how far do you space it off the tub, and what do you use to space it? I purchased Omni Grip premixed adhesive at the advise of the tile guy at H.D. He seemed very experienced. He told me to space them at 1/8″. Is that right?
Hey Ron,
It depends on whether or not the subway tile are lugged. If they are then you don’t need spacers at all, if they don’t then you can space them at any amount you think looks good (you can do that if they are lugged as well). It’s more of a personal choice.
You really should return the omni grip and get some versabond thinset which is sold in bags and you mix with water – it won’t turn into mush when it get’s wet.
Hi Roger, we are tiling a bathroom floor on a second floor. It is a 1″ floor sitting on 12″ BCI’s. at 16″ O.C. It has 25 yr. Old vinyl floor that is adhered very well. We dont want to remove it. We want to put a pebble floor down that is on a 12×12 mesh sheet. Can we do this using ditra or hardi backer? Thanks, Ron
Hey Ron,
As long as the vinyl is not cushioned vinyl and is not installed over luan then yes. You’ll need to install backerboard with thinset beneath it and screw it down well. You can either go directly to that (which is normally a better option with that pebbles or river rock) or you can install ditra. I would forego the ditra due to the size of individual rocks in the mosaic sheets.
Thanks for the quick responce Roger, it is much appreciated!
Hey Roger, what type of thinset is used under the hardi backer, and what type is used to set the pebble tile on the mosaic sheets?
You want a good modified thinset to set the pebbles, it doesn’t matter what you use beneath the backer – it doesn’t bond to anything, it’s only there to fully support every area of the backerboard.