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 
Good morning! I was doing some research and found your post about Ditra. I am working on installing ceramic tile on almost 50% of the first floor of our house and I had some questions I was hoping you could answer:
1. Can you install Ditra over Luan underlayment? It has vinyl tile on it now.
2. If you can do 1, do I need to remove the adhesive from the wood? Or just the vinyl?
3. Do I need to add more supports to the floor joists? The floor does appear the move when the kids get a little over-active.
4. Where do I need to add the movement joints? Is there a specific formula, or is it primarily where there are room transitions? Eg, front entrance to kitchen?
Thanks a bunch!!!
Hey John,
1. No, the luan needs to be removed. It can not be under a tile installation.
3. Yes. And a second layer of plywood perpendicular to the first (if plywood).
4. They need to be installed every 20 – 25 feet in both directions. It usually works out so you can put them at room transitions.
My husband and I used ditra in both bathroom remodels without a problem, but did the kitchen yesterday 12 x12. But when we went back today several areas of the floor had bubbled up. Obviously this needs to get fixed before tiling. We put the ditra down with keraset which is what the store recommended for our over plywood construction. Most of it appeared to adhere fine, but 2 of the 7 pieces laid have large bubbles in them. I’m planning to tear these up and re lay them tomorrow, any idea what the reasons could be and do I need to scrape the thinnest from the floor before attempting to reapply?
Hi Sonja,
I don’t know what store recommended an unmodified thinset over plywood but they’re wrong. You need modified thinset to install ditra on plywood. That may be a large part of the problem. The main cause is that the ditra was not embedded fully into the thinset (unless there’s actually thinset on the back of the bubbles, but doubtful). Try mixing up your thinset a bit thinner and making sure it doesn’t skim over before you get the ditra embedded. Yes, you need to remove the cured thinset from the floor where you replace it.
I am installing ditra on my bathroom floor. The subfloor is 1 -1/4″ 2 layers of plywood.
Can I use Custom Building Products FlexBond 50 lb. Gray Fortified Thin-Set Mortar from Home Depot to install the ditra to the plywood and the tiles to the ditra?
Hi Sam,
Yes, but you’ll lose your warranty from schluter. It will work just fine, though.
Thanks for the response.
Roger,
What would be a better choice? I have Lowes and Home Depot?
Sam
That will be just fine. The marble and granite mortar from home depot is really good as well as any of the laticrete thinsets if your lowes carries those.
Roger,
Thanks for the great site. We’re having to go back and redo our shower floor because it wasn’t done well. This means tiling over existing tile, because removing it might destroy the Schluter Kerdi membrane. We’ve worked out everything else (including drain height) except, our new tile guy wants to tile directly over the existing tile, using a special mortar designed for that. We were told by a Schluter rep that we should NOT put tile on top of tile. He said we should put down Ditra first and then tile. Our tile guy is doing a fantastic job and has 30 years experience. He says he’ll do it, but that it’s pointless to do it that way and is offended that we’re trusting some guy at a desk over his experience. Yet, the mortar he will use has laytex polymers that are added for flexibility, which is exactly why Schluter recommends putting down the Ditra over the existing tile. What should we do? Thank you for your help and for helping my wife awhile back. If you can possibly answer this before Monday morning 7/22/13, it would be really great.
Hi Roy,
Your tile guy is absolutely correct. I have no idea to whom you spoke but they apparently are not familiar with their own products. Ditra DOES NOT go in the floor of a shower – ever. The cavities (yes, even when filled with thinset) will hold water. Stagnant water in a shower floor is a breeding ground for all sorts of nasty stuff. Let your tile guy do his job – he’s doing it correctly. Let the rep choke on his own incompetence.
Whoa, did I just type that out loud…?
Hey Roger,
It’s Roy’s wife, Sarah. He hasn’t even seen your answer yet, but I was anxious to see what you thought, so came here to check it out. Thank you for answering so quickly! I was making out a “pros and cons” list of using the Ditra in the shower or not using it. One of the items on my list was exactly what you mentioned — the waffles and what happens if they fill up with water?
The Schluter rep said that, while they don’t warranty Ditra in the shower, they NEVER recommend tile on top of tile, but that they knew of many jobs that were successful, using Ditra on top of a layer of tile, before the next layer of tile. The main reason we would have to want to listen to the Schluter rep and use the Ditra in the shower is to avoid cracked tile(s) in the future.
Our tile guy has already said that eventual cracking in the corners is “normal.” We would like to avoid “normal cracking”, which is why we wanted Ditra on the bathroom floor. With respect to our tile guy, he is very good, there’s do doubt about that. But he’s good at “old school.” If it were up to him, he would not be using any Schluter products at all. He is closer to the end of his career than the beginning and doesn’t seem interested in hearing the science behind Schluter’s stuff — he just wants to do what he’s always done. I tell you all this only to give you some insight into the fact that, while he thinks we are biased toward Schluter which he thinks may be a “gimmick”, he is definitely biased about sticking with the “tried and true” rather than the “bold and new.”
Just an FYI, here are the instructions I typed from the Schluter rep:
1. Apply rapid modified thinset to the existing shower tile.
2. Lay Ditra (the regular kind) on top.
3. Wait for a minimum of a week before doing anything else, to give the modified thinset time to dry. (Longer dry time would be better, ideally 14 days according to what the Schluter book says about dry time being 14-60 days. See the section about why they do not recommend modified thinset with their products.)
4. After enough dry time, apply unmodified thinset and tile the shower floor as planned (as he has done the regular bathroom floor).
We are open to letting our tile guy finish without the Ditra. It would be easier, as we wouldn’t have to wait on dry time and we would have his good will.
However, we really wish there was some “insurance” against tile cracking rather than having to live with what he told us that, “it’s normal”.
Is there a particular modified or rapid modified thinset that you think would be particularly good at minimizing the chances of cracks, in the future?
Any further advice?
Thanks so much!!!!!
Sarah
Hi Sarah,
“Our tile guy has already said that eventual cracking in the corners is “normal.””
The key word in that sentence is ‘corners’. Yes, if the corners are grouted they will sometimes crack (if the shower is a mud shower) and always crack if it’s built in some other manner, it’s simply a matter of time. However, that is precisely the reason we now silicone all changes of plane. Grout cracks – silicone is flexible enough to compensate for that movement.
I do not tile over tile, it’s just not a method that fits into any of the projects my business is built around. That said it is a completely acceptable practice. It will not lead to cracking tile or grout in the tile field itself. If you want insurance against cracking have the perimeter siliconed rather than grouted. 30 years ago matched silicone was neither readily available nor field tested. Grouting corners was normal. For a lot of guys it still is – I do it sometimes. But when I do it I rely on my experience to know whether or not it’s acceptable for that particular project.
I understand your tile guy’s mindset, and it’s fine. There’s absolutely nothing wrong with old-school, I use MANY of the methods and am schooled in all of them. They work, and they work well. I know it sounds like I’m just defending his methods, and I am, to a point. But if you think about it wouldn’t you rather have him use methods he’s comfortable with?
And no matter what Schluter’s ‘reasoning’, they are there to do two things – sell products and cover their ass. I’m not railing against their products – they’re great, I use them constantly. As I regularly state, though, I can not stand the company or their business practice. I also deviate from their printed and stated instructions a LOT. But I do that because I know what will work and what will not. And I am ultimately responsible for the outcome – not Schluter.
I guarantee if something went wrong, even following to the letter of their instructions, the final say would be ‘installer error’. He should have known not to use ditra in a shower floor – ever. See? Covers their ass. When it comes down to a situation like something going wrong, in a court of law we (professional contractors) are viewed as the end-all expert of what works and what does not. No matter what the rep said, no matter whether you have a variation of installation instructions IN WRITING, and no matter what the homeowner insists on – whether they put that in writing or not.
As unfair as that sounds I tend to agree with it. Someone sitting behind a desk has limited ability to know what works and what doesn’t in real world, real life applications. Tech reps are hired to answer basic questions, given to them on a screen in front of them, and to tell you what may or may not be a good idea. NONE of that is legally binding – ever. It is up to us, as professionals, to let you know what will work and what will not. Ditra will not. Tile over tile, with siliconed corners, will. It’s that simple.
Schluter has a multi-million dollar marketing department and an 800 number, we have real world experience with everyday installations. Your tile guy is right – just get some silicone around the perimeter so that change of plane does not crack and you’ll be just fine.
Hey Mr. Elf (aka. Roger),
This is Sarah’s husband, “Roy.” We both recently posted questions and wanted to send you a big, all-caps THANK YOU for all your help and great advice. I wish there were more people like you running websites like this.
After finding your website and posting my question, I told Sarah, and she said, “Oh yeah, I’ve been to FloorElf. He answered a question for me awhile back.” We’ve had a rough year trying to repair water and mold damage.
We’ve caught all kinds of needless contractor mistakes
and thankfully prevented as many disasters, because we had resources and help from you and other professionals out there in cyberland. We also love your sense of humor.
God Bless You,
Roy and Sarah
Cleveland/Chattanooga TN
Well thanks Roy! Anytime I can help prevent the family pet from bursting into flames I consider a good day.
I didn’t read through all the other questions and comments, so forgive me if this is a repeat. My installer hasn’t worked with Ditra before and was talking about laying down the thinset over the Ditra to fill the waffles and let it set to create a level smooth surface. Then he’d come back the next day and lay the tile with additional thinset. I told him this wasn’t the right approach but didn’t want to argue given I’m not a tiling expert like he supposedly is. Thoughts?
Oh boy, I’m tired. I linked you to the post we’re on. Sorry about that, Chad!! The Schluter link is good, though.
Hi Chad,
That is actually an acceptable method and one I use often. That actually comes from my Schluter rep, although you’ll never find it in writing. Their products are geared a lot toward the diy market and they don’t like to deviate from set instructions to limit the amount of failure given too many parameters with people inexperienced with tile installations.
Pre-filling it is just fine.
Aloha Roger
Re: installing DITRA over painted plywood.
I will be installing DITRA over an outside wooden deck that is under a roof. (This is in Hawaii where freeze-thaw is not a problem. The wood is thick plywood, even, properly-sloped, in good condition. The ply is installed over joists.) The problem is the existing wood floor has many layers of paint on it. I gather that thinset (that bonds the DITRA tyo the subfloor) will not bond properly to paint. Can I get away with scarifying the paint, or do I need to remove all the paint down to bare wood?
P.S. I love your site because it appears that you know what you are talking about.
Hi Jean,
Ideally it would be best to take it down to the wood. However, I realize not everything is ideal.
You can scarify it if you use a really good thinset to bond the ditra. Laticrete 254 or mapei ultraflex II will work with it.
Hello Roger,
I will be using Ditra for the first time in a small bathroom remodel. Was watching a video where an installer set some tiles, and had a few inches of thinset, on the Ditra, past the installed tiles. It appeared that he came back the next day and continued to install the rest of the tiles. So it looks as if he had dried thinset on the Ditra, then just continued the job the next day. Is this acceptable? Another thing I’ve not seen is how to line up tiles, by snapping a chalk line. Is this done on Ditra? Thanks.
Hey Chris,
Yes, it’s acceptable to have cured thinset in the cavities. I pre-fill it often. Some guys chalk it some (like me) normally use spacers. Depends on the size of the installations – bigger ones get chalk lines. It doesn’t stay on the ditra very well though.
I have plywood floor that I want to install travertine tile on. I want to use scluter ditra. The floor is slanted on both sides from slightly high joist running through the center of 7×7 space. Should I use self leveling mix to level floor first or can I install a layer of ditra in the low spots and then another layer of ditra over the whole floor? Also does it make difference what kind of thin set i use? Thank you
Hi Gary,
Either one will work just fine. I prefer the slc, but they both work.
To start off, I love reading you comments- but also you are informative.
Now to my question. My kitchen is one the main level ( with a full finished basement under), I currently have Armstrong linoleum. I would like to put in tile, but am concerned that there may be to much movement in the floor. The ceiling fans will rattle just alittle down stairs when my four year old runs through the house. The sub floor is as follows. I joist, a thick subfloor that clicks into itself(like a laminate floor would do) that is glued and screwed down, then a layer of plywood, then a self leveler, then the glued down linoleum. Would the Ditra adhere to the linoleum and counter act any movement preventing cracking? Thanks for your input.
Hi Leslie,
No, the ditra can not be installed to the linoleum. It needs to be removed. It would be easier to remove the self-leveler with it. After you do that I would install an additional layer of 1/2″ plywood, then ditra. That should dampen the movement enough not to be a problem. It won’t stop the fans from shaking, but it won’t transfer movement through the tile.
Hi
I’m being told by a builder that Ditra can be used directly onto floorboards, is this correct or does he need OSB, if so what minimum thickness ?
Also my wife wants an acrylic roll top bath in the middle of the bathroom floor, would the point loading create a problem on the tiles laid Ditra ?
Thanks
Gary
Hi Gary,
I don’t know what you mean by ‘floorboards’. Ditra should not be installed on osb. It should be installed on plywood. If, by floorboards, you mean planks then no, there is no approval for that installation method of which I am aware.
I also don’t know what a roll top bath is, I’m assuming a footed tub. If that’s the case then no, there is no problem with point loads provided the tile is correctly installed.
Hello, I pulled up a bathroom floor to find a tar papered sub floor. I don’t want to add any floor thickness. Can I apply ditra to 60 year old tar paper that isn’t going anywhere easily? Any suggestions?
The room is a small 5’x6′ bathroom. I’m useing 12×12 porcelain tile.
Thank you
Hi Joel,
You shouldn’t. The bond of the ditra, and in turn your tile, will depend on the bond of the tar paper to whatever substrate you have beneath it. I would try to remove as much of that tar paper as you can. Thinset also does not stick to tar paper very well.
Hi Roger, we’ve installed Ditra in our kitchen up to the cabinets. We left 1/4″ expansion joints at the walls, and against most of the cabinets, but even after our careful measuring and cutting we ended up with a minimal expansion joint against some. How serious is that? Should we try to trim the Ditra away from the cabinets before tiling? Is that even possible? Also, the thinset oozed out a bit and filled some of the expansion joints in other areas. Should we try to chip that out, or does it matter? Thanks so much!
Hi Tiffany,
You don’t need large expansion joints between the ditra and cabinets, it’s important to have them with the tile and the perimeter, though. You can leave the ditra as it is.
roger, my mud bed is down & i’m anxious to lay tile. however the thinset bag says “do not use over uncured concrete (28 days)”. on the other hand, ditra says it’s ok to use over green concrete. so how does one adhere the ditra ? thanks, al
Hi Albert,
Deck mud is not the same thing as concrete. You can install ditra over it the next day with thinset.
Can I use Ditra on top of an old (1930s) tile floor? I’m redoing my bathroom and its very small tiles and they are cracked but not loose. I have enough space to account for the increase in floor height. I had someone in to give me a quote on the renovation and he mentioned Ditra and said that would be the better option as it appears that my current tiles are set directly into concrete and will be a bitch to tear out.
The floor is not perfectly level in one spot, should I pour a self leveling compound first (would that go on top of old tile?) or could some generosity applying the thinset under the Ditra address that?
Hi Mary,
Yes you can, but you must first scarify (roughen up) the surface of the existing tile so the thinset has something to bond to and you must use a thinset approved for use of tile over tile. Mapei ultralex 3 and Laticrete 254 are two of them, there are several others. Yes, ideally you should use slc (with the primer over scarified tile), but you can build up those areas with thinset beneath the ditra if you want to.
Oh good! Thanks! Is a handheld sander a sufficient way to scarify?
Yes, but it will take a while. A belt sander or a grinder with a cup wheel would be much faster (and dustier).
We are planning on getting tile installed on a 160sq.ft outdoor fiberglass deck. Do you recommended that the tiler use Ditra and or anything thing else.
We were told that as fiberglass expands and contract with temperature changes putting tile on fiberglass may be a complicated and expensive procedure.
Thank you for your advice.
I honestly don’t know that there is any viable way to install tile over a fiberglass deck without installing a mud deck as a substrate. Ditra WILL NOT compensate for the amount of movement it will experience.
We just ripped up our old second story master bathroom floor. We discovered we have 1/2″ subfloor. We are planning on installing radiant heat cable wires, DITRA and 12×12 marble flooring.
DITRA states a required minimum 3/4″ subfloor and a minimum 3/8″ underlayment. Do we need to rip up our current subfloor and put down 3/4″ thick subfloor or can we just put a thicker plywood underlayment (3/4″) on top of the 1/2″ subfloor. We are installing 12×12 marble tiles so we want the floor to be as sound as possible.
If we need to tear up the existing subfloor, how do we go about doing that? Currently our subfloor boards in this small bathroom (7×7.5) go under the walls into adjacent rooms. Most of the walls sit on the joist.
I assume that the subfloor boards need to be nailed down along the center of the joist. I am just not sure how we would go about doing this. FYI – the adjacent rooms have hardwood floors and carpeting.
Hi Michele,
You can install a layer of 3/4″ right over the 1/2″ to reach the needed thickness.
Hi Roger. The Tavy Thin Skin Glue was very hard to manage because after I would dip in out of the pail and trowel it onto the floor it was almost impossible to release since my glove would stick to it….., but of course I had to in order to put down the Thin Skin paper. I did manage, but there were splatters on the walls from my ripping the gloves loose from the trowel. In the end though the Ditra and tile all worked fantastic and it the project was a great success! NOTE: The glue was pretty easy to remove using mineral spirits and thankfully the Sherwin Williams paint did not show any trace afterwards.
Roger,
I believe I am in quite a fix. My husband and I had planned to install tile floors in our two upstairs bathrooms. We purchased all of the materials and were planning on installing it ourselves. However, an unexpected event occurred that put us in a severely limited time crunch, and with our work we knew we were not going to be able to get it done in time, so we decided to hire an installer. I called several tile installers, but none of them had ever worked with ditra (which we had already purchased). The only place that had experience was Lowes. So, we hired them to install our tile. Our bathrooms originally had linoleum (installed over 1/4″ plywood). We ripped out the plywood and linoleum and prepare for the installers. It was down to the OSB subfloor. I had noticed a couple of places where the boards squeaked (and made sure to point that out to the installer). First, we had purchased 1/2″ plywood to go over the subfloor. However, when we dropped by this afternoon, we discovered that the installer decided on his own not to install the plywood, but to rather installed the ditra directly over the subfloor. That was my first clue that things were going south. I was very upset, but he insisted it would be okay. But then, I came home this evening to discover that rather than installing the ditra over the plywood with modified thinset and then installing the porcelain tile over the ditra with unmodified thinset, he switched the thinsets. We had traveled all the way to Post Falls, ID to purchase the Custom Uncoupling Mat Mortar just to be sure we had the best product. I was livid to discover that he had used the uncoupling mat morter to install the ditra over the plywood and then the modified thinset to install the porcelain tile over the ditra. I immediately went to Lowes to report the problem. They told me that he informed them he always does it this way and would warranty the installation. I told them I had no confidence in the install and that I know he installed it incorrectly. They said they would contact Schluter to see if there was a problem and they will call me tomorrow. In the meanwhile, my bathrooms are in disrepair. We had plumber coming on Friday to install the toilets back, but the installer told us he won’t even be coming tomorrow so there is no way anything will be even remotely ready for the toilets. Are we completely screwed? What do we do? And, if I can get my money back for the installation and all the lost materials, where do I go? (we live in Kennewick, Washington).
Hi Bridget,
Schluter is going to tell them that it’s not acceptable and they will absolutely not warranty that. Lowe’s covers their ass VERY WELL with their contractors – that means they will accept no responsibility, at all, should they feel they don’t want to. It is on the installer – every bit of it. His screw up, his responsibility. I don’t have any idea what type of contract you signed with lowes but if they told you he had experience then there is fault there on them.
The bottom line is that it’s the installers fault – a manufacturer’s favorite term – installer error. “I’ve always done it like this” is just another incarnation of my most hated excuse – ‘I’ve done it this way for twenty years…’ It’s always wrong, it’s always bullshit, and it’s always their responsibility. I have no idea what you may be able to work out with lowes, but it’s my guess that’s your best bet. You can be sure that whatever agreement they reach with you the installer will end up paying for it – but that isn’t your problem. It will likely be easier to reach an agreement with them than the installer, I’m sure he won’t take any responsibility for it.
How difficult is it going to be to rip up? One bathroom has the ditra down and the tile installed on top (no grout yet). The second bathroom just has the ditra. I don’t want to damage the subfloor and I have to get the floors prepared for someone else. I have just cried and cried over this.
I have no idea, I don’t know what specific (modified) product they used, what the humidity and temperature of your home are, whether or not they mixed the thinsets properly…etc. It shouldn’t be too difficult, actually. The unmodified is bonded to plywood, which will be the most difficult to remove, and the modified isn’t likely to be fully cured yet. The sooner you get to it the easier it will be.
Hi Roger. 1st off thanks for the great site. I have also gotten some of the manuals. Very helpful! So I am using Schluter for 1st time on a big job. 4 baths and a ton of floor tile. One thing we are having trouble settling on is best way to level out some really wacky floors. The master bath is out almost 2 inches in few spots. Our tried and true method is wire lath on plywood and mud floor running at minimum 1/2″ and thicker as needed. My plan would then be apply the ditra in non mod thinset and then tile in non mod thinset over that. Is that a go or do we throw out the mud floor routine now that we use ditra? Reason I ask is have had some tell me to use self leveling….but 2″ ?? And no we cannot repair framing at this point. In addition to above we would like to install electric heat mat. Where in the sandwich does this go????? Oh oh last question we are doing a hot tub deck in same bath and owner wants wood deck around tub not tile. Any suggestions on material ? the box is being finished with wainscoting and they want to stick with wood look for the 4″ deck around tub. THANKS FOR ALL your help. It has been very helpful for me.
Forgot to add that the subfloor is the good stuff 3/4″ who’s a whatsit high grade particle board subfloor and we blocked all joints from below and doubled 3 of the floor joists to get extra strength to carry new bathroom.
Well, in that case – same answer.
woops just read instructions on posting additional q’s. Sorry!
Hi Craig,
The mud will be fine under the ditra, no problem with that. The heat goes between the mud and ditra – under the ditra. Teakwood would be ideal (and expensive as hell – but cool), but you can use mahogany or oak if you use a really good seal on it and it is maintained well.
Thanks for the reply. Teak would be cool. What is your method for leveling out a bad floor prior to ditra and tile?
It depends on why the floor is not level. If it’s not too bad I do it with the thinset beneath the ditra as I’m installing the ditra. If it’s more than about 1/4″ out in spots I’ll use slc.
Hi Roger I have Vct tiles on concrete in my basement which 15 years ago I removed old tiles which had the black adhesive I scraped chipped and spent a lot of time cleaning I prepped floor at that time with self leveling cement some dash patch installed the Vct with that white adhesives don’t know the name but the one that dries then stick tiles ok all solid still to date considering putting down well first choice porcelain tiles or vinyl glue down plank flooring If I decide ceramic can I use the ditra without removing Vct just scratching it up ? Will it last ? And how about the vinyl glue down? Thanks Anthony
Hi Anthony,
Thinset will not bond to vct. I also do not know of any vinyl glue which will bond to the face of it, I could be completely wrong about that, though. Have you thought about free-floating floors? Something like LVT (vinyl planks)? That would solve your problem.
Roger
Two quesitons for you.
I put down heat wires over plywood and covered with modified thinset. It dried fine but looks like it shrank a bit (like shrink wrap) and you can see small ridges where the wires are, maybe 1/16th or so. I want to cover with (un-modified thinset) and Ditra. Will that next layer of un-modified thinset let Ditra go over this not perfectly level floor?
Second quesiton, I installed Ditra over plywwod but got a little too much (modified) thinset under part of it. I squeezed out most but not perfectly “flat” and it appears to have good adherence. I would say variations of perhaps 1/16 from a knee or foot print. The next sheet I used less thinset and it went down pretty well and flatter with good ceverage. Now I know “less” is better than more.
Tiles will be 12 inch by 24 inch porcelain put down with a 1/2 X 1/2 inch trowel and my thought is the 1/16th inch variations in Ditra will be made up with the (un-modified) thinset over the Ditra and back-buttering the tiles?
Thanks for any comments
Hey Doug,
The ditra will go over those wire ridges just fine. The 1/2″ trowel will also more than make up for the inconsistencies in the ditra in your other floor.
Thanks for a super fast reply!!
Do you use the Schluter expansion joints, I wanted to put one in the doorway between the heated floor and non heated portion in the front entrance. There is a bit of a height transition there as well from the heat wire side. I will leave lots of room around the perimeter edges.
I did quite a bit of research first but the first job is always a learning experience! I’ve read more of your site and picked up a lot of tips.
I’ve used them and they work very well. They also look cool!
better than silicone in some applications.
I know I asked before but cannot find your answer. I tiled a kitchen floor with ditra and your help – looks great. Now I will tile a custom made built in cherry table that had inlaid tile. I cannot put ditra or cement board – no room. The surface is plywood and the old tile and adhesive is out. The old adhesive seemed kind of rubbery. What do I use to adhere it. Could I use thinset but first put a coat of polyurethane on the plywood. The border around the plywood is cherry about 6″ wide. Right now the tile I have is porcelain and 3/8″ thick. The tile that was remove was 1/4″thick and was even with the border. We have removed some of the plywood and plan to add 2 cross supports underneath. But I can only remove a little more (both sanding and routing out) without ruining the beautiful table. Got any great suggestions?
Hi Karen,
You can use either thinset or epoxy setting material. Do not put polyurethane on the wood, it will prevent the setting material from bonding. If you need it to be waterproof you can use a sheet membrane like kerdi or remove the plywood and replace it with backerboard.
I cannot remove the plywood without ruining the table. It is an integrated and imbedded part of the whole table structure. I just sanded down some of it to give more depthe. I do not necessarily need the tabletop waterproof since I would only be wiping it down and never letting it sit in water or liquid. I was more concerned that the water in the thinset would have enough moisture and be there long enough before the thinset cured to cause the wood to warp. Even the kerdi would go down with thinset which still concern me about the wood having a chance to warp in that window of curing time. Maybe I am worrying about a non issue.
It won’t warp from the moisture in the thinset unless it’s less than 1/8″ or so thick.
Hi Roger,
I am planning on installing ceramic tile on an above grade concrete slab. Red quarry tile were there initially, and they popped right off. Some black adhesive was left on the cement, which I believe is cutback. When I run my hand over the cement, the whole thing feels nice and smooth. My questions: Is it okay to install Ditra over this? What type of unmodified thinset would you recommend? Do you recommend using the Kerdi waterproofing band to seal the seams? I have pictures of the cement, if it would help. Thanks. Karen
Hi Karen,
If it’s cutback it needs to be removed before installing the ditra. I don’t think there’s any thinset that can successfully be used over cutback. Splash some water on it, if it sits on top for over a minute thinset will not bond to it.
My normal unmodified thinset is laticrete 317, but there are many available: Unmodified thinsets. If you want the floor waterproof use kerdi-band, not necessary unless waterproofing it is your goal.
I am getting ready to install my bathroom floor tile ( I am using ditra under porcelin tile) and I have a question that I have not found a definitive answer for, so hoping you can be my definitive:
– for the toilet flange, should it attach to the subfloor or to the finished floor. I have seen lots of different answers to this. I do not relish the idea of drilling holes in the finished tile so I was thinking subfloor but with the ditra and tile that will be a big height difference; what are your thoughts on toilet flange install?
Hey Craig,
The reason you haven’t found a definitive answer is because us tile guys don’t really like the definitive answer.
When done properly and by PLUMBING standards the flange should sit on top of the tile. The easiest way to do that is to mark your tile where the holes will be and cut a groove there from the inside of the circle out. That way you don’t have to drill through it and they will be covered anyway. But the proper method is with the flange on top of the tile.
Hi Tile Elf,
We bought your shower manuals and they have been very helpful. We are waterproofing the bathroom floor with shluter ditra for tile to be installed. Since the toilet flange goes on top of the tile, how do we ensure waterproof seal around the waste pipe in the gap the thickness of the tile between the ditra membrane and the toilet flange?
Hi Joe,
Place silicone around the toilet flange on top of the tile.
Hi,
Can I use Ditra XL in a laundry room (with heavy and vibrating washer), or would traditional method be a better choice?
Thanks,
Andrew
Hey Andrew,
I feel more safe with a double layer then ditra, but schluter says it’ll work. It all comes down to which you feel more comfortable with. Me, I’m more comfortable with plywood layers and regular ditra.