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 
Hi Roger. I am installing a tile floor over 3/4 plywood which is installed over car decking. I will be using Ditra and Laticrete’s Floor Warming mat. After all the layers are assembled what can I expect my finished floor height to be. I want to be sure that I have my wood threshold at the right height before beginning. Thank you. Virginia.
Hi Virginia,
I have no idea, I don’t know what you’re installing. The basic height would be ~1/8″ for the mat, ~1/8″ for the ditra plus your thinset and tile. Whatever your tile thickness is add ~3/8″ to that and that will be the approximate height of your installation OVER THE TOP OF THE PLYWOOD. I don’t know if your threshold is going down to the plywood height or the height of the car decking or something in between.
It is ALWAYS best to install your tile then purchase your threshold. I don’t know why you would want to do it the other way around.
Hi Roger
I have a 4 inch suspended concrete floor for my main floor. When it was new 7 years ago I acid stained it and epoxied it. Since I had no experience, it turned out pitch black instead of a nice brown. Now I want to tile over it. I am using 24 inch fibra tiles and the regular ditra. Tomorrow I will start removing the epoxy with a steel shot blasting machine. Crazy tough boring job I’m sure. Any special recommendations for thinset? I think the recommendation is just non-modified thinset. Is this the best?
Hey Colin,
I would use the laticrete 317 for that. It’ll work just fine.
Hi Roger,
I would like your opinion on my situation. I want to install travertine in my Kitchen. The joists are 2 x 8 16″ OC with about 10ft 7in span. Of the 10 that are full length 4 are doubled and 1 is a triple. I plan on reinforcing the single joists with steel strapping. The subfloor is diagonal planks. I want to add 5/8″ ply then use Ditra to keep the height down. What would you suggest?
Thank you,
Ken
Hey Ken,
If you double or reinforce the single joists you’ll have more than enough structure for your travertine with the 5/8″ and ditra.
Wow what a fast response, thank you very much
Ken
Hi Roger,
I bought your “how to” guides and they are awesome. To say they are a Great help is an understatement. My Dog was on fire and I was able to put out the flames.
Have you tried this product (Glue and underlayment)?
http://www.tavytools.com/bndr5.html
I plan to use this over sheet vinyl flooring and skim it with modified thinset. I plan to let that dry and then use unmodified thinset and ditra for the underlayment for the tile install again with unmodified thinset.
My vinyl was installed over 1/4 inch luan and both glue and staples were not spared, so ripping it out would be almost impossible!! The floor is very solid with no flex and the vinyl has no cushion backing on it (thankfully).
Thank you again for all your great tips, advice….and elf humor!
Regards,
Keith (in Virginia)
Hey Keith,
I have not used it, but I do know that thin-skin is a very good product and works well. (I know guys that use it a lot) Do remember that if you choose that route your tile installation will only be as good as everything bonded beneath it – that includes the luan to vinyl and the glue that bonds it. And hope it never gets wet beneath the thin-skin.
Hi Roger,
I guess I’m gonna put a soft joint in.The problem is that I wont have a doorway, it’s a 281 SF big room but as I said I am going to put a soft joint in about where the addition starts(halfway). That being said I have obviously a couple of questions more.
What size trowel should I use with 12×24 tiles and using the Raimondi Leveling System?
If it’s gonna be 1/2×1/2 trowel over Ditra XL how much thinset I will need for 281 SF. Or how much a bag let’s say of 50 lbs. yields over Ditra XL. The tiles I will use butted together already give me 1/16 joint and if I’ll use the Raimondi that also adds 1/16.Will it be enough or it’s better to make 1/8.
Thanks again
Attila
It is better, and required, to use at least a 1/8″ grout line with tile that size. 1/2″ trowel will work fine. You’ll get about 30 square feet per 50lb – you’ll need about 10 bags. bag with the XL. DO NOT butt the tiles together.
It was never my intention to butt the tiles. Butted they already give 1/16 and the Raimondi adds another 1/16.
That’s 2/16 th already but I’ll listen to you and put 1/8.
With a room of that size what would be the better way to start tiling.
Starting from one side an go from there row by row or mark out the middle of the room and lay a row lengthwise then the tile the rest.For sure I wouldn’t be able to finish it in one day and I am afraid they’ll move overnight .
Although i did two small bathrooms so far, never in my life attempted something this big.
Your input would be much appreciated.
Make a line down the center of your room and see how it lays out. If you have smaller than 1/2 cuts along the edges then shift it all over 1/2 tile. Then start on one side, you should have the correct measurement by then, and work back row by row. They will not move overnight, especially with the leveling system. It will lock them into place.
Hi again Roger,
) a white discoloration to it.It happened when I grouted the bathroom to, and I got rid of it using a full strength white vinegar wash (scrub).
finally I’m done tilling, grouting getting rid of the haze etc.
My grout which I did yesterday has (like always
I did it after a week or so and I’m not sure if this time I should wait that long or get to it right away.
Normally how long should on wait after grouting if this happens.
Appreciate it, thanks
Attila
Hi Attila,
The sooner you can get to it the better. If it’s sooner than 2 days or so you probably won’t need to use straight vinegar.
Hi Roger,
First a quick thanks. Your site has been a huge resource for me.
I have a tile project where I hope you can confirm I am on the right track.
I’ve already purchased Durock as my tile backer, but I am considering changing to Ditra if it would provide better support. Specifics of my job site and tile are at the end of this post.
I am using a 6 x 24 porcelain tile, and I was under the impression that I must use a modified thinset for best adhesion when using porcelain tile. Now that I am considering Ditra, and modified thinset will go below Ditra and unmodified thinset above Ditra, I was curious how this would work with porcelain (when a stronger adhesion is recommended).
Two questions:
1) Can Ditra be effectively used with a 6 x 24 porcelain tile?
2) Given these specs, which would provide the best support for my tile (Durock or Ditra … I am not hesitant to spend more for the right products)
Here are the specifics:
16 oc; actual measurement of joists are 1 1/2 x 8 7/8. Length of joists has a 10 ft span between supports. OSB is 19/32.
Here are the specifics of my tile.
6 x 24 glazed porcelain tile
Hey Trent,
1. Yes
2. Your best option would probably be installing an additional layer of 1/2″ ply, then thinset then the backer. It will be a hell of a lot cheaper than the ditra and will provide better support in your situation.
Can I put ditra over pexboard radiant heat?
Hi Leslie
I have no idea. I can probably give you a more definitive answer if you tell me what ‘pexboard radiant heat’ is? You can use ditra over regular radiant heat, but I have no idea what the pexboard aspect of that may be. Is it a manufacturer? Is it just called something different here? Am I drunk already? (I only had one beer in my Cheerios this morning…)
Help me help you.
Roger,
I’m going to be installing tile floors in the two bathrooms in our new house, There is 3/4″ OSB over TGIs, The osb is screwed to the joists.
-Can I put the Ditra over the o.s.b. subfloor with out buildup with additional layers? Or do I need to have the 1 1/4 in. min. thickness subfloor, then install Ditra? This floor meets l480 standards.
-Should I use latex modified thinset for both the Ditra and Tile installation?
Thanks
Hey James,
If the floor meets l/480 then you should be fine with going over that. Ideally you would have the additional layer, but what is ever ideal?
If you want your warranty intact you need to use modified below ditra and unmodified over it.
Great site Roger…..quick question regarding tiling a bathroom floor and using ditra……
When adding a new layer of subfloor (5/8″ tongue and groove plywood onto existing 3/4″ tongue and groove slats) what’s your take on intentionally avoiding sinking screws from the new subfloor into the joists?….and only screwing the 2 layers together between the joists?….
Regards
Hey Jim Bob,
That is the proper method, and the better of the two. It creates a separation layer with your top layer that does not move exactly like your joists or bottom layer – expansion and contraction are dissipated through the top layer if it isn’t screwed into the joists.
Great Site! Quick question, Schluter recommends a minimum 2″x2″ tile when using tile. I would like to use 1″ hex tile over ditra. I’ve read on another blog that if you install the ditra as recommended then skimcoat with thinset, let it dry 24 and then install the 1″ hex you should be ok. Any thoughts?
Thanks,
John
Hey John,
Nope, not really. It will still give you the same cured product either way – so you are still using tile smaller than 2×2 on ditra. The issue is that the 1×1 tiles are not completely supported, some portions of nearly every tile will be directly over the high part of the ditra – the part that frames the waffles. That area is not supported.
If you think about a cured ditra installation like your tile sitting on little pillars it’s easier to understand. With a 12″ tile the pillars fully support the tile, because the pillars are 3/4″ apart. With 2×2 or smaller tile you are attempting to balance those tiles on those pillars rather than supporting the tile with the pillars. KnowWhatIMean?
Thanks! What would you recommend as an alternative to Ditra that would work? The floor is going over 3/4″ plywood over 3/4″ plank subfloor over 2x10s at 16″ OC.
Hi John,
Please read through this answer I posted: Posting questions Thanks.
Spidermat from custom, Prova-flex by loxscreen, or GreenSkin by Devcom would all work. I would recommend Greenskin, spidermat, prova-flex in that order.
Hi Roger,
I got the greenskin. I also have ditra set from Bostik (which I bought when I was going to go with Ditra). Would you use the ditra set as is or modify it (with Bostik 425)? I asked Greenskin directly and they didn’t have a definitive answer.
Thanks,
John
Hey John,
Use the 425 with it, it’ll be a more sound installation. Greenskin is good stuff! I like it.
Hi Roger,
Last year I built a 12’x15’ addition (dining room) to my existing kitchen which is 10’x13’. In the new construction we used 2×10 at 10 inches o.c. which gives me a deflection of L / 892. The subfloor is ¾ Advantech and I was planning to put Ditra XL and tile over it. According to the Shluter website I can do that. My problem is the existing kitchen. I only have a 5/8 Advantech subfloor on IBeams placed at 19.2 inches o.c. The tiles I have now in the old kitchen were glued to a 5/16 plywood, fastened with “staples “ to the 5/8 Advantech subfloor in order to meet with the hardwood floor in the living room. I already have three 12×12 cracked tiles were the plywood sheets were butted together and I also have a ¼ inch sagging in the middle of the room. Here the floor doesn’t meet Schluter’s specifications to install Ditra and I don’t know what to do. Since they are I Beams even if I rip up the floor I wont be able to sister them. I cannot jack them up because the room in the basement is finished. I was thinking to pour a self levelling compound to level it then put the Ditra XL down but since the subfloor is only 5/8 I am afraid to do that, I am wondering what other options do I have left without going higher than the hardwood floor. I am thinking hiring somebody to tear up the floor and put some additional IBeams between the existing ones(at 9” oc ) in and shim the ones are sagged and bringing the floor straight and level. I am planning to install 24×24 or 12×24 ceramic tiles on Ditra.
Thanks
Attila
Hi Attila,
There is nothing you can do short of adding the beams and shoring up the sagging ones as you’ve described. That is the only way to build it up to a proper substrate. You can probably get away with 1/4″ backer with thinset beneath it then ditra XL or 3/8″ ply with ditra XL over it.
Hi Mr.FloorElf(Roger)
Thank you for your quick answer to my question!
I just had a contractor look at my floor(not really look because it’s still with tile on it)and telling me that he might not be able to add some additional beams between the existing ones because of the electrical wires that might be passing between the joists but he could reinforce it adding blockings at every 2 feet or so properly fastened(glued,screwed) and then also reinstall the 5/8 t&g Advantech.
My question is how well in your opinion a floor could be reinforced just adding blockings and if I would get away putting Ditra XL on it and tile it with 12×24 tiles. Initially would have liked 24×24 but since my subfloor is not going to be a proper subfloor I just gave up on that size.Would you thing 12×24 would be okay or I will have to go back to 12×12.
If of course you agree that reinforcing it by adding blockings it’s going to be enough.
Thanks again for being here so I (or people like me) wont burst on fire!
Attila
Hi Attila,
The blocking will significantly stiffen up your floor and should work just fine. Tile size: It makes no difference whatsoever. I know that sounds counter-intuitive. If you have a 24×24 inch tile it is four square feet of tile, right? If you have four 12×12 tiles it’s four square feet of tile, right? If you have two 12×24 tiles it’s four square feet of tile, right? All three of these take up exactly the same amount of floor space. All of them will be placing the same amount of stress, strain and weight on every square inch of the floor as every other size. One square foot of tile is one square foot of tile.
What you need to be concerned with when using larger tiles is the flatness of the floor – it needs to be flatter than one on which you can use 12×12’s. That’s it, weight-wise it’s not an issue at all. Ditra XL should work fine – for any size you choose.
Thanks Roger
My question about the big sizes was because I’ve read on some forums that bigger the tile easier it will snap if you have deflection issues. That is why I was afraid to put bigger tiles.About the flatness , the addition is pretty flat and if we manage to take up the the 5/8 board, and fix the stiffness and deflection issues, the kitchen floor should be acceptably flat too. I guess. I was planning to invest in a Raymondi leveling system to bring the tiles even.Any thoughts on that?
Thanks
Attila
I heard it works well. Sometimes I use the tls, but same concept. They work.
Oh, as far as the ‘snapping tiles’ – a grout line will become debonded from the tile (cracked) before you’ll be able to snap one of those tiles in half. They won’t snap unless you have ZERO support. The grout lines will crack first – long before that. If you see cracked grout again it may be a problem, but you’ll still have the same issue with 12×12’s. The larger format actually spreads the load over a greater area (bigger footprint) so point-load deflection is diminished, they’re actually a better fit for a less than adequate floor.
Happy to have found you site Roger,
you just put my mind at ease. I guess I’ll be okay after all. I might go back to bigger tiles depending on how well the “stiffening” will go.
Thanks again
Attila
Hi Roger,
I just called Schluter to see what brand of modified thinset I should use to glue the Ditra to the Advantech board and they said that any premium brand latex modified will do the job.
Do you have any brand in mind I could use?
I have access to Mapei,Tec,Customblend, Ardex, no Laticrete though.
Thanks
Attila
Mapei ultraflex is good, so is versabond. Versabond is made by custom. Customblend is not a brand, it’s a product of custom (a garbage product
), but if you have access to it you likely have access to versabond as well.
Hey Roger, thanks again. I’ve just read your post on soft joints
and since my kitchen and dining room is going to be 21′ long and 14 wide I was wondering if I need to put a control joint in. The room gets only some late afternoon sun trough the patio door. My concern is mostly the transition between the dining room and kitchen where they are attached together. This comes about halfway the length (10 of the 21”). I am not really expecting the new construction to move but… Foundation of the new construction is on metal posts some of the screwed down to 15′ so it’s pretty solid.
Thanks
Attila
You should be fine with no soft joint in that provided you have perimeter joints around the entire perimeter. If it were my installation I would place a soft joint between the two rooms.
*Something only tile guys know: If you watch people walk through a doorway they hardly EVER step in the middle of the doorway. They don’t walk on thresholds and normally step into the other room without stepping in the middle of the doorway. Weird, right?
Try watching sometime. That is an ideal spot for a soft joint.
i want to tile over galv metal shower walls can i thin set over metal then apply kerdi membrane, or should i use 1/2 “kerdi boardand deal with the extra thickness
Hey Bob,
You should install wet mud over the wire lath. That’s why the wire lath is there. Thinset will not work. If you want to use anything else (kerdi-board) then remove the wire.
Unless you’re talking about actual metal walls (which is how you worded it) in which case it can not be tiled, the metal will need to be removed.
You are the lime in my Corona Roger!! Thank You!!
I am tiling a bathroom and a small bedroom in the same 12×24 rectified and fully vitrified porcelain tile (3/8” thick). I am in southern California with concrete slab for the whole house.
There is a crack in the bathroom floor (both sides level, but goes through about a third of the room) so I got some Ditra (1/8” high) for just that room to protect the large format tile from the crack. There is no cracking in the bedroom. I intend to eventually tile the whole house in large tiles.
1) Should I use Ditra in the bedroom as well? Is it something I should use throughout the house? If not how do I address the transition between Ditra & non-Ditra rooms?
2) If no Ditra is needed in the other rooms, then what thinset do you advise for the concrete slab? Modified? What are your favorites (Laticrete I am sure
but which one)?
3) Fellow grout hater here (but I would rather do it right)-can I do 1/32” grout lines or would 1/16” be better? I will be using the SpectraLOCK epoxy grout for stain resistance.
4) What notch size trowel do you suggest? Different for below the Ditra versus between the Detra & tile?
5) I have animals (and their puke and a rare pee). Will there be a significant value to sealing the vitrified tile? If so, then do you suggest the Miracle Sealant 511 Impregnator?
Thanks so much for your help!
P.S. While it is horrible on floors, a Cool-Aid moustache looks great on both kids and adults
Hi Angela,
1. If you’re going over concrete everywhere it’s always a good idea to use ditra throughout. Whether or not it’s currently cracked it likely will be to some extent in the future. Concrete moves a lot (really), ditra is always a good idea.
2. My preferred laticrete thinset is 252.
3. 1/16″ would be better, 1/8″ would be even better. With large format tiles you need larger grout lines, especially if you’re doing any type of pattern.
4. 1/4″ or 3/16″ under ditra, 5/16″ or 3/8″ over, depending on the flatness of your slab.
5. The acids contained in the bodily functions you’ve mentioned will damage the grout regardless of sealer. Sealer does nothing against acids.
Thanks for the post on ProvaFlex – I almost bought it, but now its going to be ditra, no more cement board, to much work screwing and glueing(I’m to old)., I’m doing my kitchen (450 sq ft)., osb over 16 oc joists., questions: thinset and trowell size for the bottom and thinset and trowell size for the ceramic tile on top…thanks
Hey Chuck,
I normally use a 3/16″ trowel under ditra. The trowel size for the tile depends on the tile and the flatness of the floor. If they are both relatively flat then a 5/16″ or 3/8″ is fine.
Roger I am going to be installing floors for Empire Today but I’m a little leary about being resposible for a 1 yr warranty on labor. They use a(garbage) 1/4″ pressboard (not OSB) as a sub-floor for vinyl tile and sheet vinyl. I think they use the same pressboard and DITRA for porcelain tile. They expect the installers to do two jobs a day. I asked if I’m supposed to go back and grout the next day and they said they use fast set thinset and grout the same day. I have never used DITRA before or fast set for a whole job. This just sounds like alot of potential call backs or insurance claims. I thought you couldn’t use fast set with DITRA. Before I do a tile job I would like your feedback. PS Times are tough and I need work but I’m getting a bad vibe from the Empire Today ways of installing flooring. During the interview I was told that they are a “floor covering” not a “flooring” company. Which I guess means the floor just needs to look new not stay new. I don’t think my work ethic is going to let me work this way. Thanks.
Hey Rick,
It’s entirely up to you. I wouldn’t touch it with your insurance, though.
If they do not want or allow a proper substrate then I wouldn’t be willing to guarantee it. Remember, if it fails it’s not their problem – it’s yours. If you don’t feel comfortable putting your name on it – don’t.
Fast set thinset is allowed with ditra, it works well.
Well, i am in love with this website-not really-i just like it a whole lot. With that said, i have a painted block wall in a basement that i would like to tile over. It is stable, but has a few pops in the paint due to mositure. A title contractor told me he would tile right over that with expoy and it would be fine. A second tile guy-uninvited, showed up with the drywaller-claimed it had to be blasted clean of paint then tiled. Last but not least, the tile store said to screw hardiboard to it.
So, i am confused for sure-but i will believe you, reading over the site and appreciating your concern for man’s best friend. It will be the best answer.
Many thanks in advance
jim
Hey Jim,
Well, the tile store is full of shit. (Not surprising)
The epoxy option, which MAY work, is still dependent on how well the paint is bonded to the brick. Whether or not he uses epoxy the strength of the bond of the tile to the paint is fairly irrelevant, right? It’s the bond of the paint to the brick that’s holding your installation in place. If you have bubbles from negative hydrostatic pressure (that’s why you have bubbles) then when that happens in the future in a different area your tile will become unbonded from that area as well. The tile will be well bonded with epoxy to that layer of paint – the one that just peeled off your wall. You would be hard-pressed to remove that tile from that paint.
The uninvited guy is correct. The best option of the three is to remove the paint, mechanically or chemically, and go from there. It’s the only option where your tile is actually bonded to the brick (or your membrane). You can also bump out the wall with a 2×2 or 2×3 frame and screw cement board to it, then just install as you would a normal shower over framing.
Hi Roger,
We installed Ditra two days ago, and of the 200 SF in our kitchen, it did not bond very well to about 20 SF. It’s odd, as it was in hte middle of a batch of thinset (not at the end), and it seems just fine at first. Then teh edges started to curl, and as we tried to push the curls back down, that entire end of the Ditra started to go wavy. I am really hoping we don’t have to pull up that section of Ditra, as I am sure getting the thinset off of the plywood is going to be a nightmare. Do you have any thoughts?
Thank you!
Nora
Hey Nora,
Wavy or not – if it’s now bonded well to the substrate you can tile over it. You’ll just have to take care to get your tile flat over that area. As long as it’s bonded it’s fine.
I am working on helping my parents redo their kitchen floor. We removed the subfloor and linoleum over their concrete slab already. After researching, I realized we cannot use backerboard over the concrete so the alternative is Ditra. The concrete slab is about 1 1/4″ below the hardwood floor it butts up against. The Ditra XL seems like the perfect product for us to use. After thinset layers and the Ditra XL product and the heigth of the tile it should be the perfect thickness. My dad has asked a couple of contractors in the area (they live on the Centeal Coast of CA) & they have’t used Ditra before. They have suggested using self-leveling compound to build up the thickness and then tile on it. I think that would be difficult to do over a space of 350 sq. ft. Do you think the Ditra XL would work for our situation? The tile we are using is 18×18 travertine.
Hey Lincoln,
The ditra XL will work, as will the SLC. Either one will work fine if properly installed. I’ve done slc over a floor that was just over 2200 square feet – 350 feet can be done.
I am going to install 12 x 24 porcelain tile with infloor heat mat and Ditra over 5/8 T&G plywood. I have been told to do this a million different ways and not sure what to do. I was going to use Nivex self leveling cement to burry the mat. Do I have to use primer before using the SLC? After the SLC is set what type of mortar do I use? I have been told that I should use Profix 8500 with latex Profix 6500 that install the Ditra. Is this correct or can I just use regular modified mortar? After that I was told to use unmodified mortar to set the tile. What is the best way to seal off the perimeter of the room and any openings before pouring the self leveler? Do I have to worry about leaking a gap between the wall and the self leveler? Any advise would be greatly appreciated.
Thanks
Hi Stephane,
I have no idea what the brand that you’ve mentioned is, we don’t have it around here and I’ve never seen it. You can use an slc over your floor heat, it’s a good idea. You DO need to use the primer. It’s normally easier to install the primer, then the floor heath, then the slc. That way you’re not trying to install the primer over and around your wires or mats. Regular modified mortar over the slc is what you want. Pink expansion foam around the perimeter and wooden blocks for heater vents and such. Put tape over any gaps.
I am installing ditra…the only problem is that we had to replace parts of the subfloor due to rotting and now the new subfloor has a lip. Will thin set even the lip out so I can install the ditra right over top?
Hi Kimberly,
Yes. Just use a straight-edge when you embed the ditra and you should end up with a flat substrate.
hey roger,
I want to tile a concrete slab in my basement that has had several issues
with hydrostatic pressure. the problem has hopefully been relieved by installing an interior perf pipe into basin system. still there are hairline cracks in the slab that show moisture. im guessing due to capillary action.
im highly considering using ditra, but am still concerned about the thinset drawing more moisture from those cracks and causing failure. and if it does draw moisture where does that moisture go? ditra boasts it ability to manage vapor, but im full of common sense and the concept only seems
kinda right. I did consider using a red guard type product, but my same fear holds true. what approach would you take to this application?
thanks
Hey Greg,
The redgard won’t work, the hydrostatic pressure will debond it from the slab. The vapor management properties of ditra allow moisture to dissipate through the channels on the bottom side of the ditra to the perimeter of the installation. Any vapor or moisture WILL NOT cause thinset to fail. It is water stable once cured. I would go with the ditra.
ROGER,
How do I handle my ditra/tile to toilet transition? My plumber left me with a Sioux Chief Gasketed Closet Flange to insert when my tile was finished. Do I run the ditra and tile right up to the toilet cutout and then diamond drill the flange down on top of the floor? Is there a way to waterproof the transition to the pipe (slap hydroban on there) or does it need to move on different plane?
Jerry
Yes, diamond drill holes for the flange and fasten it to the top of the tile. You can silicone the transition, but there’s absolutely no reason to. The wax ring between the toilet and flange seals it. If you are concerned with any type of water penetration outside of that wax ring then you have more problems than that particular transition.
I’m pulling up two layers of vinyl sheet, each with 1/4″ underlayment. The Schluter instructions seem to indicate I can right onto the subfloor with modified thinset for the Ditra. Is that acceptable practice? If I have to put in 3/8″ underlayment I’m betting I’ll have to modify my cabinets so the fridge and washer fit, which I’d obviously rather not do. Yes, the floor seems quite solid with no notable deflection; 3/4″ OSB on 2x10s at 16″ OC.
Hey Doug,
If you’re using regular ditra you still need the double layer of plywood. If you want to stick with the single layer ditra XL is approved for use over a single layer 3/4″ ply.
Roger…… I need to install tile on a concrete foundation in an area that adjoins a room with hardwoods. I need to make floors same level which is about 1 1/4″ – 1 1/2″ difference. Area is 13′ x 10′. What is your suggested method to build up the tile floor area? Tile is 3/8″ thick basketweave.
I thought of using 1/2 Hardieboard set in thinset on concrete slap (no nails??) & then use Ditra on top of that OR shoot down 3/4″ treated plywood & then Ditra. I’m really at a loss for the best way to build up floor…….it’s expensive tile that needs to last ….. forever
Hey Brantley,
Deck mud. Anything you install to the slab like ply, backer, etc. won’t really lend itself to long-term durability. Deck mud is the most stable and long-lasting substrate for an installation over concrete. I’ve torn out mudbeds that were literally 70 years old, and only because they wanted to change the tile. They were in better shape than a lot of new floors I see.
Greetings Roger,
I am installing tumbled slate tile in an entry-way that has (after I rip up the linoleum) a base of 3/4″ tongue and groove hardwood on top of the subfloor. My house was built in 1908 and, as most homes this old do, has some creaking in the floor. My question is, do I rip up the 3/4″ T &G hardwood and build a new OSB base then Ditra or leave the 3/4″ and install the Ditra on top of the T&G or is there a 3rd option I am not considering? Thanks for your feedback and time!
Hey Chris,
You should be able to secure the current 3/4″ to the joists to stop the creaking, install ditra then your tile.
Hello Roger,
I stumbled upon your site and have been reading and learning,but just got confused-imagine that!
Anywho,I thought that you had stated that when putting down a subfloor above a pre-existing one(say a subfloor going down on top of the floorboards that are attached to the joists-the old floor had to come out)do not screw the new sub-floor all the way thru to the joists just screw it to the pre-existing floor for expansion reasons.
And your response to Chris to cure his creaking floor is to screw the 3/4″ t&g thru the sub to the joists-isn’t this the same as what you said shouldn’t be done or am I mixing up my do’s and don’ts or double negatives or…*POW*(head explodes)
Thanks,I’ll hang up and wait for my answer:)
Hey Art,
Ideally the second layer should not be screwed into the joists. That, however, is with a flat floor which has no creaking. If there are already two layers and the floor creaks the only way to properly attach the first layer of ply to the joists, as it should have been done originally, is through the second layer. It is not a deal-breaker, just better practice.
Every ‘rule’ about preparing a substrate which is followed diminishes the chance of having problems. There are very few of these that, alone, will cause a floor to fail. The more rules you follow the less the chance of failure. Substrate preparation is all about diminishing chances of failure. Sometimes something needs to be done that breaks a rule, but ends up with a better substrate. Having both layers firmly attached to the joist is a hell of a lot more sturdy than having it moving beneath your tile installation.
Nice to know someone’s paying attention, though.