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.
I just laid ditra over plywood, but didn’t immediatly lay the tile over that. Time restrictions. As I was laying a skim coat over the ditra I noticed that there is alot of moisture on the underside of the ditra. Is this going to be a problem? It has been twentyfour hours since I laid it.
thanks.
Hi Julie,
Why do you think there is a lot of moisture under the ditra? I assume because there are random areas which are darker? If so, that is just where the thinset has saturated the fleece on the backside and is in direct contact with the polyethylene. It’s normal. I don’t think there is excess moisture – the plywood would have soaked it up.
Is that what you see and why you think that?
What do I do if my Ditra joints with their tape are higher than what I expect to set my tile into when I spread my thin set for tile installation?
Take the tape off. Why do you have tape on a ditra joint? If you are talking about kerdi-band, it should be right against the ditra – it should add less than 1/64″ to the top of your ditra. If that’s a concern you’ve either installed way too much thinset beneath your kerdi-band or you are not installing nearly enough thinset beneath your tile.
Hi Roger,
I will be tiling my exterior concrete pad (450sqft) with porcelin tiles. I have one cold joint and I understand I cannot run ditra over that but that I can run it over the control joints without issue. I’ve been told that I need to use some sort of flexible grout at regular intervals and at the cold and control joints. I have a few questions I hope you can help with:
1) I am thinking of using Mapei Kerabond Dry Mortar between the tile and Ditra, is this OK? Laticrete seems to be 2x the cost…
2) Other than voiding the Ditra warranty, is there any advantage, disadvantage to using modified thinset between the ditra and concrete? Do you have any recommendations?
3) Can you point me in the right direction for the flexible grout that would be needed? I read some info on Urathane vs Epoxy grout and they both look like a pain in the butt and possibly trouble for an outdoor install.
4) I will be using a combo of 12″ and 6″ tiles; should I be back buttering both?
5) I’ve read on your site and others that some use a two step approach when applying thinset over Ditra, one to fill the waffles and two, to attach the tile to the waffle-filled Ditra. Recommendations on which way to do this? If I do it this way, how long do I let the thinset -set- before applying the tiles?
Thanks in advance for your help; it is much appreciated!
John
Hi John,
1. Yes, the kerabond will work fine.
2. Modified thinsets add ‘stickiness’ and a bit of flex in the bed of thinset itself. Versabond is actually a good thinset for that application.
3. What you need in the control joints is Flexible sealer (silicone), not flexible grout. Depending on the exposure and facing direction of your installation (direct sunlight) both the urethanes and epoxies may have problems. Most grout manufacturers make colored silicone which matches their grout.
4. Yes, if given the choice backbutter everything, especially in an exterior installation.
5. You can do it all at once or do the two-step method, really doesn’t make a difference with the finished product. I do it so I can install the ditra and walk on it while installing the shower and not crush the waffles. Just fill the waffles one day and tile the next if you choose the two step method.
Roger,
Thanks for the info. So for the flexible sealer do you mean that I put the sealer in the control joints? I was under the impression that I needed movement joints in the installation. Can you help me understand this a bit?
Thanks!
John
You do need the flexible sealant in the control joints in the tile. Any tile installation over 12 feet needs to have a soft joint. Any installation going over control joints in concrete need a soft joint directly above the concrete control joints (and saw joints). The joints in the concrete need to follow up through the tile installation. The sealant (not sealer – two different things) is to fill that joint so it doesn’t just remain empty and can still compensate for movement.
Those joints in the concrete are where your concrete will move – the tile will move as well – you are compensating for that. Read through this and it may help: Control joints in tile installations
Roger,
My existing kitchen floor is tile on a concrete slab. We’re in the process of planning a remodel and I’m considering tiling over the existing floor. Can Ditra be used for this application? If so, what would be the proper thinset for laying the ditra? Any other challenges to I need to consider before proceeding?
Thanks for your help!
Hi Greg,
I don’t know – you did not say what your existing kitchen floor is. You’ve only mentioned concrete. If going over concrete then yes, kerdi will work. Unmodified thinset for both under and over.
If you currently have tile in good shape you can scarify the surface to remove the shiny portion and install kerdi over it with a thinset approved for tile-over-tile installation. Mapei ultraflex 3 and Laticrete 254 Platinum is another. It will say on the bag whether it is approved for that type of installation or not.
If you currently have something else you’ll need to let me know what that is.
Roger,
I just had a flooring company who I checked out and was noted in our city paper as the “Best Flooring Company” install tile in our kitchen using Ditra and after the installation we discovered about 1/4 of the tiles sounding hollow when tapped… 311 Sq ft. The installer and owner came to our house today and blamed it on the Ditra. The owner offered to have the Ditra Rep come by our house and take a look… we accepted and I don’t think she expected us to say yes by the expression on her face.
Our floor is concrete. My wife and I prepped the floor and made it as clean as possible. we removed the old leveling adhesive that was under the exsiting floor. It was obvious where the low spots were. The installer commented it was the best he had seen.
Why do we hear hollow areas in the tile and what are the causes? Also the istalled tile is not level in places…. a low area in the concrete about 3X3 and we have some lippage issues. Should the installer be responsible to install a level tiled floor?
Why do these business owners think we have to accept the poor services they provide?
Any help would be great.
Hey Harold,
Hollow sounding tile over ditra could be due to either improper / incomplete coverage or bond with either the ditra to the substrate or the tile to the ditra. The good news is that I can nearly guarantee you the installer will be the responsible party. Let me guess – he didn’t use unmodified thinset? It’s not imperative to the tile not sounding hollow, but it is absolutely imperative if he expects that Schluter will accept any responsibility at all with that installation. They won’t.
It is absolutely the installer’s responsibility to install a flat floor. Even if you did the prep work and they attempt to blame it on that (I’m guessing that’s their next move) they are responsible for both knowing that it was done improperly and fixing it or bringing it to your attention and work with you to address the problem. They’re the ‘professional’, correct? I am by no means saying it’s the fault of your prep work, I’m just telling you what to expect from their big book of excuses.
I would like to thank you for demanding the problem be addressed! The reason they expect it is because people buy their bullshit excuses all the time. They hire subcontractors who are not, or are barely, trained at all – let alone properly, and pay them crap wages. Even if they have to pay to replace a job like yours every now and then they still roll in the cash. It demeans my profession and really, really pisses me off. So thank you for not accepting sub-standard work.
Roger,
Thanks for the timely reply.
My wife and I had thought we had done our home work finding a good installer. The add they have in the local paper says “We do it right” and they have been in business over 53 years in the local area. The only thing I thought was odd was we could not find any positive or negetive reviews on them online. A few people had tile work done by them and they were satisfied.
Next week the Ditra Rep will come by if the owner sets up the appointment and we’ll see what he says. I can’t believe he would say that the floor is good. At that time if he agrees with what you and we have been saying we’ll demand it be fixed.
One comment the owner made was… “If we remove the tiles to do the repairs it will not look the same as the original installation”. Again this will be unacceptable.
On the lippage.. the owner took off her shoe and rubbed her feet over the problem areas and said ” Oh that is acceptable”. Not to us…. when you can look down the run and see one corners sticking up in the tiles. We used a dime and anything higher that that we considered lippage. Mostly it was uneven tiles with high corners. They never did mention anything about the floor having problems. If they had we would gladly have said please fix that.
We paid 1/3 of the cost for the job to start but until we are satisfied they will not get any more money from us.
All we are asking for is a solid level tile installation. I don’t think that is asking too much. We are the customers. Trying to get people to do good work these days is tough. I need to go over to her house and check her tile.
I wanted to pull a few of the loose tiles but my wife wants to wait till the rep comes.
If I had the time I think I could had done a better job. At least I know how to read instructons.
Yes it has us rather torqued too!
I’ll let you know how this turns out.
Roger,
The nightmare continues…..
Yesterday the owner of the flooring company came over with the “Rep”. The “Rep” said that because of air pockets in Ditra the tile was acceptable. I knew this was BS since I had already written Schluter and had your info. I read aloud and presented Schluter’s info for them and they didn’t seem to want to do it correctly even then. I had tile books, the newspaper clipping for them that says “We do it Right”, all the info from Schluter etc. After I vented on the owner about why we picked them due to their reputation she offered to extend her warranty for another year and fix the most of the tiles. So that gives me 2 years. I want the floor to last 20 or more. I told her I was very unsatisfied and I wanted it fixed.
This morning I called Schluter and found out the real Reps name for our area and discovered that the person she brought was just a salesman. I confronted him this morning when they came and asked for his qualifications and connection to Schluter. I asked for a bussiness card. On it is only “Sales Represenitive”. He said he sold Ditra products but had no connection to Schluter. BUSTED! After that he just didn’t say anything as I was pointing out the problem areas to the installer.
After that I again told the installer I had marked all the tiles needing fixed and he said he would do whatever it takes to make us happy. Now we are back to my total amount of tiles with hollow sounds. Of course they didn’t bring enough materials to do anything so I told them to schedule all the work when thay have everything and he said next week.
They have to fix 1/3 of the floor for loose/hollow tiles and excessive lippage in the traffic areas.
Thinking about it now maybe I should have had them rip up the whole thing and start over.
Anyway…. that is where we are.
So for all those people out there that have hollow sounding tiles on Ditra…. don’t accept it.
There is a problem if it does not solid.
“Hollow sounding tile is typically due to (but not limited to) improper thinset coverage on the bottom side of the tile. Not backbuttering the tile may contribute to this.”
Call Schluter, They were very helpful and they have a great product if it is installed correctly.
Thanks for haivng a site so others can read and share info.
I’ll let you know how it comes out when they do the repairs.
Roger,
I guess we raised enough hell…. got a call this afternoon from the owner of the flooring company and they are going to replace the whole floor.
I’ll give an update on that when they finish next week somtime.
Hey Harold,
Thanks for the update! It’s likely a combination of two things – first, I’m sure you raised enough hell – thanks!
Secondly, if Schluter were to hear about what happened the salesman’s dealership privileges for any schluter products would immediately be revoked. If it were me I would absolutely make that happen! I can’t stand these people that take something this far simply because they screwed up, they know they are at fault, and to prevent losing a penny they instead attempt to take advantage of people and screw them over.
You are not responsible for their lack of ethics, I would make his ass pay for it in a heartbeat. These people are the ones who give my profession a bad name, that’s why I started this site. I’m sick and tired of contractors and shops taking advantage of homeowners – it makes my job more difficult. Thanks for raising hell!
Roger,
They came in and pulled up all the tile and Ditra. What we saw was lack of adhesion of the mortor on the tile. Every tile had spots where the mortor took and then nothing… the back of the tile looked new with nothing on it. We guessed that he didn’t butter the backs or he didn’t have his mortor wet enough. I couldn’t tell you about the Ditra condition due to the mess and he had it out before I could get a look. We took pictures of the tiles.
After he pulled up all the tile I figured he would have to re-prep the flloor but he poured leveling compond all over the floor with the fuzz left over from the Ditra felt. Pictures too.
Next he started to lay the Ditra again and some tile. I noticed he was not filling the Ditra cavities completely with the mortor. And his mortar looked dry. I questioned him on his trowel size because he was using a 3/16 X 5/32 for the Ditra and a 1/4 X 1/4 for the tile. Pictures where you can see the Ditra between the tiles with no mortar in them.
I called Schluter about the Fuzz left on the floor and pouring the leveling compound over it and they said it would be ok.
I had to go back online and look things up again and Schluter recommends a 1/4 X 3/16 or a 5/16 X 5/16 for the Ditra and for 13X13 Ceramic tiles you should use a 1/4 X 3/8. I just wanted to make sure it was going to be done right this time. If it wasn’t important they would make one trowel size for everything. Recommended is not required but I had to say something.
He didn’t look happy and stormed out and said he was going to go get some trowels. In 5 minutes he was back grabbed all his stuff and said he had been doing this for 16 years and this was coming out of his pocket. He got in his company van and left. I figured if he had been doing this for so long he would have every trowel size needed for any job. Figured if he had been “School Trained” on Ditra he would know to completely fill the cavities.
An hour later the owner comes by and says there is nothing they can do to make us happy and we ended our contract. In her Schluter training notes she said the trowel sizes were acceptable.
I had had enough anyway and she saved me the effort to tell them to get out.
My wife and I scrambled to another tile company and have someone coming over today for an estimate. Between my wife and me we’ve burned almost two weeks of vacation to get thiis done.
We did deposit a 1000 dollars but they dropped off all the tile for the Job. We asked about Ditra but they didn’t bring over any.
A funny thing is we ran into someone we know in Lowes and was telling them about our tile situation. When we mentined this company she said they were “Crooks”. Checking into a company doesn’t always work as we found out in our case. Another comment was made to not use any tile company in our small city.
I would love to plaster their names all over the internet to warn other people.
We are going to be putting some reviews online about them. I think they need to take out the “We do it Right” in the newspaper add. Maybe this installer was just plan bad.
My wife and I just want a solid, flat tile job that is going to last.
I’ll update on the next installation…..
Nightmare finally over. We hired another contractor to install our tile and due to the cost involved with re-preping the floor back to the concrete base we were not able to use Ditra. At least he knew how to install tile. We were happy with the tile installation. Only problem was this contractor messed up the thresholds where the tile meets the carpet and would not come to fix it unless I gave him more money. I told him I thought that was part of the job and he said that was the best he could do. I wasn’t going to give him any more money and since we have carpet work to do maybe they will be able to fix it.
I also had to call him after he left to come clean up his mess and all the residual tile and buckets he left. Why do they want to empty the buckets right outside my back door?
Anyway… tile is done and we are making some progress with the kitchen remodel now.
We’ll be taking the other company to small claims for the extra money we shelled out and 7 days of vacation I had to us from work.
Thanks for your time and virtual ear!
Hey Harold,
Glad you finally got it (semi) worked out! Talk to the carpet guys when you hire them, they will be able to shim or bump up the carpet, or whatever needs to be done, to make that transition a bit more manageable.
Oops I used ultra flex 2 for tile in a swimming pool…is this ok or do I need to start over.
I don’t have any idea why that would be a problem. What are you worried about?
The info on the bag states that ultraflex2 should not be submerged…I have a concrete pool and the waterline is about halfway on the tile…I understand the ultraflex 2 can get wet…but not submerged. Should I have used epoxy?
Oh, I did not know that.
(I’m not a swimming pool guy). Your best bet would be to call mapei tech support and ask them the limitations of the ultraflex 2. They would be the ones to give you a definitive answer.
Hey Roger,
I can’t seem to find Laticrete 317 in my area. The local tile store carries Pro-Spec and they say the unmodifiied product is good. Would you recommend the Pro-Spec, or would I be better off using a modified thinset like Flexbond or Versabond, knowing that it will violate Schluter’s warranty.
Thanks!
Hey Ed,
The ProSpec is manufactured by bonsal – it’s good stuff. That will be fine.
Great, ProSpec it is. Next question: I am adding 3/4″ plywood on top of the existing subfloor, and before the Ditra. There are a few places where the subfloor dips 3/8″ or so. What is the best way to handle it? Modified thinset? Speedset from Custom Building Products? Since SLC requires a wire mesh, there would be no way to feather it out, correct? Lastly, where should it go..between the subfloor and plywood, or between the plywood and Ditra?
Thanks a bunch!
Hey Ed,
Not all slc’s require mesh. Some can be feathered out. You can also use a floor patch, which is kind of like an unsanded thinset. The speedset will work also. Whatever you use should go between the plywood and ditra. The layers of ply need to be attached directly together or it creates a weak spot.
Hey Roger,
Thanks for the quick response. Of the three, SLC, floor patch or speedset, which do you recommend? Any particular manufacturer?
Thanks!
Of the three the slc is definitely the best option. For a very thin finish over a small area I prefer custom’s levelquick (?). My second option would be the floor patch, most of which are nearly identical from manufacturer to manufacturer for your purposes. That said – I hate speedset.
So you may actually prefer that – it’s never near the top of any of my lists.
Ever.
Thanks for your help on my previous question, I was able to get the infloor heating down and the Ditra on top fairly level (a bit wavy in a few spots). The “problem” I am having now is the online thinset calculators say it should take 25lbs our so for my tile floor and I apparently went through that much on 5 tiles. I’m laying 12×24 tiles, using a 1/2 trowel and back buttering them. I would say that the they end up around a bit more then a 1/4in higher then the ditra. Do you think I will have problems? Here is a photo: https://plus.google.com/u/0/113121679860376757370/posts/j9jKk2PLSRZ
Hey Lee,
You’re just fine. Your coverage is correct – the online calculators are inaccurate.
Thanks for the quick response! Now I just hope the Kerdi doesn’t fall off the walls when I put the tile up:) I don’t recommend doing full 8ft. sheets your first time using thinset.
Oops.
I should write that down somewhere around here for people.
Hi Roger,
I am redoing my kitchen and incorporating the dining room space. Some of the existing floor is linoleum and the other is hard wood. My contractor says I need Durock and a Ditra layer before tile. Would it be a big mistake to use the ditra over 3/8 plywood subfloor then tile (skipping the Durock) layer? The tile will go from the original kitchen to a part that was an addition 20 years ago and the floor is a little uneven at the transition. I don’t want to cheap out but don’t want to spend extra money.
Thank you!
jill
Hi Jill,
Yes, it would be a mistake. The recommended substrate beneath ditra is a double layer of plywood totaling 1 1/8″ – 3/8″ isn’t even close. A layer of 3/4″ plywood and the ditra directly over it would be ideal.
roger-
!!
back to the ditra I have an unmodified tec and a modified tec that says I have to add this stuff in a jug to it to have the plywood stick to it. Is there a modified thin set that I can use right out of the bag…versabond is the only one locally.Any suggestions would be appreciated thank you.. Putting down tommorow morning. Also do you suggest waiting any particular amount of time between putting ditra down and installing the tiles. Not about ditra but how long is too long to wait to grout after tiling? thanks
Hey Misty,
Versabond will work fine – I use it a lot too. You can begin installing tile right after you get the ditra down – no need to wait. Normally 24 hours after you’re finished installing tile you can grout it. That depends on the cure time of the particular thinset you’re using.
good morning Roger-
you say I can use versabond . Do you mean just add water to it and apply it directly to the plywood no additive right????? Like I said with the sturi set by Tec you have to buy this stuff in a jug add it to the thin set before applying it to the plywood and ditra. Sorry if my question seems repetitive but again versabond with water and go.. The consistency should be like what?
Thanks again you are such a gift to all of us diyers!!
Misty
Yes, just water. The consistency should be like thick pudding.
Hi Roger!
I realize this is an old post – hopefully you will still respond.
I am attempting my first tile project in my basement. The house is 35 years old, with a concrete floor in the basement. The bathroom is an L shape, with about 48 sq ft of floor to tile. The original flooring was sheet vinyl, which must have had a felt backing, most of which is still on the floor! I’m having real trouble getting it up, and I am trying to avoid caustic chemicals, since I have two young children (one only 2 months) in the house.
I am thinking of using Ditra for my anti-fracture membrane. Will this install over the felt backer, or will I need to get that up? The Ditra installation manual says not to install it over waxy or oily residue – but this is neither (I think). I have seen some references to scarifying, and I’m not sure what that is, although it might be my answer. There is also a concern that the adhesive used on the sheet vinyl is asbestos-based (the house was built in 1978, and I think this floor is that old), so I’m not crazy about working with it any more. What do you think?
-Pensive in Pennsylvania
Hey Brad,
The felt does need to come up. Even if it’s as old as 1978 it’s unlikely it has asbestos. Have you tried to soak it down? Normally if you pour water over it and let it soak for ten or fifteen minutes it’ll loosen up the glue and will scrape right up. If you install the ditra over it you are only installing the ditra to the felt, you would be relying on the bond of the felt to the concrete for your tile installation.
In a small bathroom remodel the solid bamboo plank flooring over concrete substrate was removed. The bamboo was 0.6 inches thick. The new porcelain tile is 0.4 inches thick. There’s a threshold from the bathroom to a main room where the bamboo continues. Can I still use the Ditra with the tile and keep the transition to the same thickness as the rest of the bamboo? Meaning, will the overall thickness of the Ditra be 0.2 inches? Also, the contractor did have some difficulty removing some I the bamboo leaving patches of the adhesive behind. Since I’m tight on space I’m assuming I should try and remove the adhesive but should it be removed even if there isn’t room for the Ditra? It probably covers 20% of the surface (difficult to estimate, really).
Hey Dean,
The ditra plus thinset should be about right. You can add extra thinset where needed. Yes, the adhesive needs to be removed.
roger, thank you for the prompt reply. While applying the skim coat of thin-set, I noticed a 1/8 swale about 2’x2′ in the middle of the floor…can i fill this with the thin set and let it fry over night?
If not, how should i proceed?
Yes, you can fill that with thinset and let it cure. As long as it isn’t deeper than 1/8″ or so it’ll be fine.
Hi Roger – are you related to the Keebler guys? I am about a week or so away from following the Ditra instructions for a porcelain tile job in a small bathroom (about 6′ ‘x 7.5′). All Ditra specs have been met for subfloor (3/4″ OSB glued and screwed on 16″ OC 2×8 joists, each one sistered with bolts to true 2×8 LVL’s further reducing the OC space). I got the joists/LVLs as level as I could, and installed the subfloor a few weeks back. Now, as I am getting the walls plumb and level (100 year old row house – not fun and should have done this before the subfloor!) I am noticing the subfloor has a slight slope starting in the far left corner – that corner is high. The opposite corner and the rest of the floor are level and flat overall, the exception being a couple of moderate dips (1/8″ a deepest point over approx 2′), but no bumps that I can see. I have read your floor level/flat floor posts which were a big help in understanding this, and have searched high and low for the answer to a couple of simple questions, but have not found them. Hoping you can illuminate.
1) How much “out of level” is too much? In this case, it is about 1/4″ out over 4′ (basically arching out from that far left high corner).
2) Are the 1/8″ dips excessive, and if so, should they be filled in with something other than thin set?
3) Is a combination of a slightly thicker thinset under the Ditra and over the Ditra a way to solve these issues?
4) Is it ok to use a self leveling compound (SLC) with Ditra? If so, is there a SLC that has a minimum thickness appropriate to the out of levelness indicated here (1/4″)? I don’t want to build up the floor if I can avoid.
5) I am also planning to use either those QEP LASH leveling plastic tabs/wedges, or the Tuscan. Any thoughts on either of these, if needed at all? Tiles are 12’ x 18″ porcelain. Might set on a diagonal as room is likely not square…
Appreciate your responses/insights as I get ready to follow Ditra instructions and get this done!
Hi P.P.,
1. specs call for a maximum of 1/4″ over ten feet with no more than 1/16″ over any single 1 foot length.
2. They are a little excessive, but I’ve dealt with much worse. Thinset will work fine.
3. It is one way to solve it. There are many.
4. Yes, slc is likely your best and easiest option. You can use ditra over it. Any good slc can be poured to 1/4″ or less. Many can be feathered out.
5. I use the TLS with most of my natural stone. It is a very, very good system. It is spendy with the initial monetary layout, but it’s worth it.
Hi Roger,
I’m removing ceramic tile from a concrete floor in a bathroom. The concrete floor is in a condo on the second floor and is about 35 years old. I’m removing the thin set with a chisel and I’m lucky the size of the bathroom floor is only 35 sq. ft. I am lightly damaging the concrte while chiseling because i am tring to get the concrete exposed. i have some areas, where I have chiseled the thin set smooth, but not off; do I have to remove these areas? They are numerous, small,and about the size of half dollars. What do I do with the chipped concrete?
I plan on using Ditra on the floor then ceramic tile.
Hey Bill,
Just get as much off as you possibly can. You should be concerned with the height of the leftover thinset, not the width or length. That won’t matter. When finished you can skim coat the floor with thinset to get it flattened out and fill any voids in the concrete.
Hi Roger and thank you for the prompt reply. While skim coating the concrete with thin-set, as recommended, I noticed a swale that is about 1/8″ deep and 2’x2′ in the middle of the floor. Can i fill this swale with the thin-set and let it harden overnight, then apply thin-set and the Ditra over it?
Also, I know i am to use unmodified for both the Ditras and the ceramic tiles. My only options to purchase the thin-set are either HD or Lowes. Which thin-sets would you recommend from both, just in case i go to one and they don’t have it in stock?
I plan on using a 1/4×1/4 trowel to lay the Ditra and a 1/2×1/2 to lay the tile. Are the sizes correct and does it matter whether I use V or square notched?
Thank you for your help!
Hey Bill,
Yes, you can fill that with thinset and let it cure. As long as it isn’t deeper than 1/8″ or so it’ll be fine. (again
)
At lowes you can get mapei kerabond or laticrete 317. If they don’t have either then buy it somewhere else. You need a quality thinset when using unmodified. Home Depot has one unmodified – customblend – I wouldn’t tile a dog house with it. Don’t even bother with it, it’s powdered mud.
Your trowel sizes are fine.
Hi Roger,
I am installing Ditra Xl through a hallway and into a new laundry room. The floor in the laundry room was an addition and is 3/4 ply and the hall is existing 3/4 osb. I am putting down 13inch porcelain tile. my question is whether or not i can run the ditra and tile through the door way into the new laundry room or if i should stop and start at the door with a marble threshold.
Thanks
Dave
Hey Dave,
Run it through there. The ditra will help diminish the transition between the two materials.
thanks.
Dave
Roger,
I observed ditra being attached to a wood subfloor with staples – – no modified thinset. When I questioned this technique I was told that the staples allow the ditra to move somewhat independent of the subfloor and thus prevents cracks in the tile and/or grout. Your thoughts are greatly appreciated.
Hey Patrick,
I don’t know who fed you that line of bullshit but that’s exactly what it is. I’m not sure if they are purposely trying to save steps (and money) or if they simply don’t know any better, but stapling ditra down is not going to work. EVERY area between the staples IS NOT attached to your substrate. These will all be hollow areas beneath your tile.
The fleece on the bottom of the ditra attaches the membrane to the substrate. The dovetail cavities and the fact that thinset does not adhere to the polyethylene is what allows in-plane movement in your tile installation. The stated benefit is correct, the method is not.
The fleece on the bottom of the ditra HAS TO BE ADHERED FULLY TO THE SUBSTRATE! Really. If tile is installed over that the grout will begin cracking within 2-4 weeks – I can guarantee that from all the way over here.
Thanks!
Hello Roger,
I’m in the process of building a new house and will be installing a fair amount of floor tile. I plan on using ditra mat on top of 7/8″ OSB, and will be installing 12″x24″ porcelain. My question is regarding the steps recommended by the manufacturer during layout. After laying down the ditra, the manufacturer says that I can fill the voids in the ditra and start laying tile in one step. I did this method the previous and only other time I’ve tiled and found it quite difficult to do my layout. The local tile store told me that I can do this in two steps, first fill the voids in the ditra, let it harden and do my layout lines on this. Then the next step would be to install my tile. Do you recommend this as well, or will the thinset not bond properly, which is my fear?
I appreciate your response,
Shaun
Hi Shaun,
The ditra cavities can be pre-filled as you describe, I do it all the time. The thinset will adhere to the top of the cured thinset in the cavities just fine.
Hey super cool guy. I blew it! I installed ditra at a friends house and I reversed the thinsets. I used unmodified under the ditra and modified between the ditra and porcelain. Is it going to fail. All else is done properly.
Hey John,
It should be fine provided you used a good unmodified and there isn’t a lot of walking on it for a day or two.
I recently installed Ditra over plywood but screwed up by using Laticrete’s 317 unmodified to bond the Ditra to the plywood. I know I screwed up as I was supposed to use a modified mortar for Ditra to wood and unmodified to bond porcelain to the Ditra but the job is done and I’m worried sick ???
Any thoughts ? Is this job doomed to fail ?
Jerry
Hey Jerry,
Not doomed to fail at all.
No worries, 317 is a very good thinset and it should be fine provided your floor is built correctly.
Hi thanks in advance for your help. First time tile install. I have a 3/4 plywood subfloor joist 16oc .Can I now put down the ditra and what kind of thinset do I use to attach it to the pkywood and then what kind to attach the tiles to the ditra. Where there is gaps in the plywood do I put anything in these, is 3/4″ thick enough. I ask about the thinset brand and modified vs unmodified because I have read soooo many different views. Thanks
Hi Misty,
You normally want a double layer of plywood totaling 1 1/8″ beneath your tile. If you are installing ceramic or porcelain then you’ll likely be fine with just the single layer and ditra. It is always best to fill the gaps in the plywood with silicone so no thinset gets into them. They are there for expansion purposes, filling them with a cement-based product defeats that purpose.
Use modified thinset to attach the ditra to plywood and unmodified thinset to attach tile to the ditra. I prefer Laticrete products – 253 gold for modified and 317 for unmodified. That said, any Laticrete thinset is a good one.
thanks roger-
I am installing porcelin or ceramic one of them so I should be ok. If I was to put more subfloor down I already have the 3/4 how much would get me to 1 1/8th? can I do something inbetween? thank s
Misty
Another 5/8″ layer of plywood will get you to the height you need. No need for anything between the layers – just screw the top layer to the bottom layer.
Good morning Roger –
I went and got the 5/8th only to realize the total comes to 1and 3/8th I think? also now my vanity will run into my outlet & my recessed mirror to close to sink, & will have to cut the bottom of my sheetrock to have a gap for tile to go under (thats what I was told to do since tile will be running up wall to 48″. What is the proper sheetrock gap? The floor I am putting Ditra over is about 11ft long by at the most 4ft wide. Because I sistered the joists and put blocking inbetween the joists do you feel it would really be okay to lay the glazed porcelin 20×20 tiles over the one layer. If I do add any more ply could it be thinner…what would be the minimum that would do any good over the 3/4″ that was just put down. Also when it was all tore up (built in the 60’s) the only substrate was 1/2″ ply under the tiles. Also the only unmodified thinset I can find is Tec and then versabond for the modified what is your suggestion to use. Can I use the versabond for the modified (to attach the kerdi and ditra to floor and walls and then use the tec for porcelin (unmodified) to attach tiles to kerdi and ditra. Sorry so long but I just want to do it right. Lastly how do you suggest I do where the tile on the floor meets the tile going up the wall I have read where you do not put tile under the sheetrock gap you end them with a gap between wall and floor tile (like when laying hardwood floors, and same with walls and then use caulk to fill the gaps? what is your thought? thanks
Misty
Hi Misty,
*ENTER* key – just sayin’.
You can use 3/8″ over the 3/4″ if you want. If you are using ditra you’ll likely be fine over the 3/4″ since you built up the floor. You can use versabond under and tec over – no problem.
You DO NOT need to cut the drywall and run everything under it – that’s bullshit. Leave a 1/8 – 1/16″ gap between the drywall and substrate and tile. As long as the gap is smaller than the wall tile is thick you won’t have a gap. Leave that gap, leave 1/16″ between your floor tile and wall tile and silicone that gap.
roger thanks sooo much you have made me feel so much better. I actually found a place that selld Tec which makes a modified and unmodified thinset and am going with that. Love your advice on the gaps that is very informative and helpful. Yesterday I read that you should run {sill seal} under everything and like a corner fold on the substrate up the wall therefore covering the sheetrock gap -which makes a movement joint?? Have you ever heard of this? I fbought sill seal yesterday. If I can find where I read this I will send you the link. As far as filling the gaps with silicone..what kind? Are they all flexible? Wow .. one more question I have this big plastic mixing valve w/this plastic cover on it and have no idea how close or underneath to run the tile/thinset/kerdi-any hints on this because once its done you cannot pull and push into position it would break all the tile work?? have a wonderful day I am soo thankful for your help and insight you are awesome!!!!
Sill seal is not needed, but it won’t hurt anything. Any 100% silicone is going to be the same – yes they are all flexible. Cut your tile to within about 1/4″ of the plastic ring around your control valve. The escutcheon (trim ring) covers the tile around the valve once you’re finished.
roger have another thought.. When the new subfloor was put down (the 3/4″ I mention) there are no movement gaps in that because the walls studs etc are nailed into it only at the door is there a gap is that ok? Also the tub was installed so that by accident there is a gap under the apron. How do I run the ditra and tiles up to this. Do I put them under it or do I hope that between the thinset ditra thinset and tiles that it butts up to it like it is suppose to(I think?) also do I put a joint os silicone there also thanks
misty
The gap at the door is fine. Run everything to within about 1/16″ of the tub apron then fill it with silicone when you’re done. If you can slide the ply and ditra under it you can do that as well, but leave the tile away from it.
Planning to tile a screen room floor, cement slab, using Ditra and porcelain tile. Since this room will be somewhat exposed to the elements (Kentucky), do I still use unmodified thinset for both the Ditra and tile? What brand? Which grout do you suggest?
Thanks!!!
Hi Marcie,
Yes, according to Schluter (the manufacturer of ditra) you still use unmodified thinset. Do not worry about the stability or durability of the thinset because it is unmodified – it actually cures stronger than modified thinset.
I prefer Laticrete 317 thinset as my unmodified and Laticrete grouts as well. All of their grouts are great. If you want the most durable use SpectraLOCK.
I’m using the 1/4 x 3/8 trowel recommended for the unmodified thinset to install 13″ tiles on Ditra. I used Latricrete 254 to bond the Ditra to OSB. It seems to hold well. On top of the Ditra I used Latricrete MegaBond. I ‘m seeing inconsistency from bag to bag when I apply tile. It seems that even though I try to be very careful about uniform thinset thickness, some tiles start lower than another just laid. I apply more thinset but end up compressing tiles that have too much mortara and cleaning out the grooves. Is MegaBond the wrong thinset?
Thanks for your thoughts.
Hey Scott,
Nope, megabond it just fine for your installation. It’s just one of the idiosyncrasies of tile setting. The more you practice the more you’ll get a feel for how much thinset you need where. It’s practice more than anything else. Welcome to my world.
How flat is your floor? That has a tremendous amount to do with it as does the consistency in your tile.
Hi Sarah,
No. Paint over concrete is what is called a bond-breaker. The paint seals up the pores of the concrete. As thinset cures it grows crystals into the pores of the substrate to bond. If the pores are sealed up it cannot do this. While it may last a little while, it will become loose over time. The thinset simply cannot get a bond to it. You need to remove the paint from, or scarify the surface of, the concrete before attaching anything to it.
Hi Roger, We are thinking of re-installing porcelain tile in our basement, after adding a french drain to deal with groundwater coming up. Hopefully we’ve solved the bulk of the water problem, but in case we ever have moisture again (eg, at the expansion joints), we’ve heard conflicting views about what tile and install is best:
-should the porcelain be glazed to add an extra layer of water-proofing up top?
-should the grout be epoxy to be more waterproof, or do we want the cement floor to breath a bit through the grout?
-should we instead install a waterproof layer like ditra under the tile?
Thanks for your input.
Hi Alexis,
Porcelain does not resist water because of the glaze. It resists water because it is a more dense tile due to being fired in the oven twice. It is not, however, waterproof.
Epoxy grout is waterproof. The ability to dissipate moisture is imperative over a slab, though, so probably not a great idea.
Ditra would be your best bet. Not only can it be made waterproof, there are channels beneath the membrane through which moisture can be equalized. It is a thermal break, which neutralizes any vapor problems with your concrete. And it is always best to have your waterproofing beneath your tile rather than relying on the tile. Membranes need to meet specific standards – believe it or not, tile doesn’t.