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 
Roger-
Thanks for the response in a different thread about proper substrates.. You helped me decide which tile installer to use by confirming the proper layers of substrate he suggested on my second floor condo with plywood and gypcrete flooring.
You said the guy who said gypcrete/thinset/decoupling membrane/thinset/tile was the correct combination. So it will be plywood/gypcrete/gypcrete sealer/thinset/DitraXL/thinset/tile.
My next question please:
Is it acceptable to install my new kitchen cabinets over the above substrate minus the tile?
Or should I just buy the extra tile to include under the cabinets?
This is what my installer is recommending just installing the cabs over the the above substrate minus the tile. He will then tile to the footprint of the new cabinets.
THANK YOU!
Matt
Hey Matt,
That’s just fine. No real reason to tile under them unless you plan on changing the cabinets in the relatively near future.
Roger,
I’m preparing to put some Ditra over SLC/warmwire in my bathroom, and then 12″ ceramic tiles over the Ditra. My understanding is that I want unmodified thinset both to install the Ditra and to install the tile. I have read your suggestions for high quality unmodified thinset here: http://floorelf.com/unmodified-thinsets-a-users-guide
1. I would like to get something off of your “preferred” list but I am having a hard time finding it. Do you have suggestions of where to buy in/near Denver?
2. I have read many people suggesting that you can use Versabond over and under Ditra because it is “only lightly modified”….Is this true (can I use Versabond for my application), and what in the heck does “lightly modified” mean, anyway? I tried to find numerical data…not really able to.
thanks.
Hi Steve,
1. You can get laticrete 317 from Design Materials in Denver.
2. You can, I have and do regularly. But you’ll lose your warranty. And there is no definition for ‘lightly modified’, it’s a bullshit justification to me. If someone wants to use modified just use it, no need to make up false justifications for it.
Thank you!
Design Materials is “Open to the public, sells to the trade”, so that’s out. Laticrete lists Bedrosians as carrying the full line of tile products, but I think they may only sell to the trade as well (will check).
Can order kerabond from Lowes. There is a 2 week lead time — probably enough time for my versabond to dry.
I’m glad to hear that you use Versabond regularly. I don’t give a damn about the warranty. If you use it, that’s good enough for me.
Q: Any special drying instructions for the tile side with Versabond (again, 12″ ceramic tiles). Fill the waffles ahead of time?
Oh, yeah – I forgot the exciting news. My shower passed the flood test! Same feeling I got when my car actually started after I changed the timing belt. Definitely good enough for this:
(I have been saving that up fro something good, you know…)
It’s not necessary but filling it the day before is always a good idea.
For informational purposes in case another Denver area reader needs a source for quality unmodified:
I found that Florida Tile sells Tec 337/338 “Uncoupling membrane mortar”, which is approved by Schluter and on your “first choice” list. (Yes, I’m actually excited about thin set)
Florida Tile does not sell directly to the public, but you can *easily* buy it by calling Mann Mann / Jakor flooring and telling them what you want. They take your credit card over the phone, and you pick up directly from Florida tile. Pricing through Jakor has been fantastic compared to retail. (FT also sell Kerdi membrane, kerdi boards, Ditra and plenty of other goodies)
Thanks Steve.
When putting down the pre fab tray, can you use ditra-set thin set on top of osb? The bag says to use 100% Bostik 425 multi purpose acrylic ad mixture. Representatives are saying I don’t have to use that. What is your opinion. Does it nullify the warranty?
Hi Valerie,
You need to use what is required by the product unless you get a written statement from the rep stating what you can use, otherwise you lose your warranty. I WOULD NOT use unmodified thinset over osb for anything.
Roger: I am planning on putting down ditra over 3/4 OSB 2nd flr, joists are 16″ o/c. was going to use modified Mapei ceramic tile morter (Lowes) under the ditra. do you know of anything that Lowes or HD carries for unmodified for over ditra and under the porcelain tile? Trying to keep this learning experience as painless as possible.
Hi Steve,
If lowes doesn’t have kerabond you can usually have them order it in for you. Any unmodified hd carries is junk.
Hi Roger,
Great website!
I am tiling an office and prepped the subfloor. Last weekend I poured self leveling and this weekend I worked used approved modified mortar under the Ditra. It worked pretty well. But just wanted to check whether this is okay to do with Ditra before I get to the tile.
Thanks,
Dawn
Hi Dawn,
Schluter wants unmodified between ditra and slc, so you don’t have your warranty any more. The good news it that it works just fine, and the warranty doesn’t matter anyway.
Help I am installing bathroom and shower marble tile floor. 12 x12 in bathroom 2′ x 2″ in shower area. I am trying to over kill the water proofing as there is a dining room below. I have installed dal seal / noble seal to the floors and to the walls in the shower as instructions. Can I now install ditra to the dal seal and water proof this as well before tiling? I need to build the floor up and I do not want to use hardi backer as there is in floor heat below dal seal. In thought uncoupling was the way to go but want to be sure?
Hi Michael,
Yes, you can install ditra over it, but I wouldn’t waterproof it. No need to and you may be creating areas to trap stuff between the two barriers, that normally leads to mold.
Thanks Roger!
Mold is no good.
There are a few air pockets in the noble seal due to what I think is the xlt setting too quickly as the in floor heat was on. It is quik trak so the tubes are directly under the noble seal ts. Should I jeopardize the waterproofing and cut and re stick these holes or will the floor be fine. I plan on using modified thinset and ditra xl then unmodified thinset and the 3/8 tile to finish. The floor is 6′ x 12′ in the bathroom and 6′ x 3′ in the shower.
I would cut them out and patch them. You don’t want voids under floor tile.
Hi Roger,
The bathroom floor is amazing. I am preparing to install the shower floor and need to build up 1/2 ” so the 1/4″ x 2″ x 2″ shower floor tile will come to the correct elevation/ 1/8″ above drain. Is 1/2″kerdi board a better solution for this pre sloped floor as opposed to the ditra xl?. I have never used kerdi for under lament in shower floor but it seems to me it is better to have something that will not wick water into it if in the event the drain becomes plugged. What are your thoughts?
Respectfully,
Michael
Hi Michael,
Kerdi is not an underlayment for a shower floor, it is the waterproofing membrane for a shower floor. Your shower floor should be fabricated from deck mud, which can be built up and shaped to whatever size you need. I’m not sure what you are trying to accomplish here or what you are doing with your shower floor. Normally deck mud is used to create your shower floor, then kerdi is placed over it to waterproof it, then it’s tiled.
I Roger,
Yes, this floor was pre sloped, the slope was built in to the floor system. It is a 36″ x 72″ shower with a linear drain along the 72″ back wall of the shower. The floor and drain was set up for 3/4″ slab material but has now changed to a less slippery surface of 2″ x 2″ tile that are 1/4″ thick. I have previously prepped the floor with the noble seal TS and need to build up on top of the noble seal to accommodate the thinner tile being installed. I am wondering if thin setting the 1/2″kerdi board would be better than hardi backer or cement board as I can not screw into the noble seal below. What are your thoughts.
Respectfully,
Mike
Hi Michael,
It may or may not work. You are looking to place a solid product in an environment where it will be constantly saturated, yet still need to conform to compression factors which will be present in your shower floor. I don’t believe kerdi-board is what you want there. While the waterproof abilities of it are perfect for your application the long-term durability of an application such as that has not been tested to my knowledge. Backerboard has. If it were mine I would remove the TS and install an additonal 1/2″ layer of deck mud and re-waterproof it. That would be the correct solution. Anything else really couldn’t be guaranteed to work long-term.
Installing ceramic tile in the kitchen. I am using ditra underlayment over concrete slab. I am not really concerned with waterproof floor so, do I need to “tape” the seams of the ditra in the tile field and waterproof the edges?
Hi Michael,
Nope, not unless you want it waterproof.
This one is under the category of how badly have I screwed up.
I’m installing 12×12 porcelain tiles over an OSB subfloor using Ditra. I bought my supplies and set the Ditra with Mapei modified thin set. No issues there. I’ve done it before and all seems fine.
However, after starting the tiling late in the day, once done I realized that I had grabbed the wrong thin set bag when mixing and I used the modified to lay about 20 sq ft of tile.
Before I continue, did I screw up badly enough that I should rip it up? Or can I convince myself that it will be ok as I’ve already done by using the excuses that,
a) the humidity in the house at this time of year is ~30% so it will dry ok
b) it’s been down for about 72 hours now, without grout
c) I’m only telling folks here so when it fails I can claim ignorance.
Advice appreciated.
Hi Mark,
It’s fine. I’d just leave it.
Morning Roger
I have used modified thinset under hardi backer, then unmodified under ditra, then un modified to set 12 x 24 floor tile, we left the area under vanity without tile but filled the waffles with end of unmodified thinset…. Now we are piecing in the tile under the vanity, would it be a fatal error to put modified thinset to set these last few tile under vanity if the thinset in the waffles is unmodified?
Thanks a bunch, we are out of unmodified but can get more in a day or two to prevent the dog from catching on fire. Connie
Hi Connie,
Yes, you can use modified to set that.
Dear Tile God:
Putting tile in laundry room ( concrete slab floor ) It has linoleum on it now,
I went to scrap it off and the linoleum separates from the paper backing. Can I tile over the paper backing that is glued to the floor and still get a good bond ? if not, is there a product that will activate the glue so I can get it off the floor ? Its important for “my dog” to do this right !!
Thanks
Chuck
Hi Chuck,
Yes, there is a super-secret ingredient that will reactivate and soften the glue – water.
Most of those adhesives are water-based and will soften when soaked for about 1/2 hour.
Thanks !!
Hi, Roger. Can I use Kerdi in place of the rubber waterproofing membrane in my shower? I’d be grateful for any installation advice, as well. Thanks in advance.
Hi Ed,
You can, but it negates the advantages of using it as a topical membrane. It will still be waterproof. I’m assuming you want to do that because you aren’t using it on the walls? If not then just do a single slope and cover it with kerdi, then tile.
Can Ditra be installed over luan plywood? I’ve heard all the horror stories about luan. The luan is glued down and nailed with ring-shank nails. Could I seal it before the Ditra?
Hi Gerard,
It can be installed over luan, but it won’t work for a tile installation. The problem is not with the way luan is attached, nor whether or not it’s sealed. Luan is not dense, it compresses. No matter how much you nail it down, the wood itself will compress through the body of it.
I am planning to install new 13” x 13” ceramic tiles on my basement bathroom [16’ x 6’]
The concrete floor was poured about a year ago, medium to smooth coarseness texture; no voids, leveled.
I’ve noticed that a hairline crack developed along the 6’ width. Do I need to apply a Crack Isolation Membrane or should I just ignore it?
If a Crack Isolation Membrane is recommended, what is the most suitable product to use?, additionally, should I use a sealer on the floor to promote thinset adhesion?
Thanks you for the advice.
Doroteo A.
Hi Doroteo,
You need to use a crack isolation of some sort. Redgard would be the most readily available. Do not seal the concrete, it does not promote adhesion, it hinders it.
Hi there.
Installing ditra over an old concrete slab with a layer of cutback residue on it. The only thinsets approved for use over cutback are modified, like versabond or flexbond. I’ve read that you can install modified under ditra if you give it a week to dry…. But always us modified over. does that sound right?
Hi Tom,
No, that doesn’t sound right. You don’t need to give it a week to dry. It never hurts, but it’s not really needed. And unmodified over the ditra beneath the tile.
The extended dry time for the thinset under the ditra is to allow more time for air to flow through the fleece before I tile the top with unmodified.
The problem is that I can’t use unmodified over the cutback residue…. What do you suggest?
Many other posters out there saying that modified is used over plywood for the same principle. I just can’t sort thru the conflicting info. Can I coat the floor with a scratch coat of mod, and then use the unmodified under the ditra?
I never said don’t use modified under the ditra. I understand what the extra time is supposed to be for, I’m simply stating that you rarely need the extra time. You can (have to) use modified beneath the ditra over cutback. The open air cavities beneath the ditra allow air flow and pressure stabilization beneath the ditra whether or not you already have the tile installed over it. You can also skim-coat the floor, let it cure, then install the ditra, but do it with modified.
Modified is NOT used over plywood for that reason, modified is used over plywood to prevent cracking with expansion and contraction of the wood. Unmodified thinset is brittle, modified – not so much. Regular seasonal movement of plywood will crack unmodified thinset and allow the ditra to become unbonded.
Roger,
After installing the Ditra on a wooden subfloor I have noticed “pockets” where the ditra did not stick to the subfloor. This may be due to the thinset being drier than it should, or not as wet as they suggest, but I do have good bonding elsewhere. Am I to remove the Ditra and start over again to correct this issue of pockets? I notice the pockets the next day as I walked on it in some areas and it just isn’t bonded. I would say I laid down about 100 sqft of ditra and roughly 4 sqft overall has pockets. Is this not acceptable?
Additional info:
The thinset used was modified as stated in the instructions. The tile that will be placed on the Ditra is a 12″ x 24″ carrera marble over unmodified thinset.
I appreciate your help.
Thanks,
Peter
Hi Peter,
You can just cut out the parts that are not bonded, scrape down the old thinset and install new, then replace the ditra. It can be patched in.
Hi Roger-
I am installing ditra over OSB. There is some paint on the floor – over spray from when the house was painted – do I have to get it off before installing ditra? I am using mapei ultraflex 3 if that makes a difference. Thanks in advance for your help.
Hi Amy,
Try to get as much of it off as you can. It can make the thinset become unbonded.
Pray tell!Can I use ditra unmodified thinset over wood subfloor ? This is what I purchased according to directions! Now modified or unmodified is my quiestion after reading your advise !
Hi Kat,
To bond the ditra to plywood you want a modified thinset. To bond the tile to the ditra you want an unmodified.
Hi Roger,
Thanks for your helpful advice on Ditra.
We have a 4 year old addition to our kitchen which is 14′ in width and above a new crawl space which abuts to the house’s original foundation. The 12″ tiles which were installed for the flooring have never broken, but the grout around them has cracked around the area where the old and new floor meet. We suspect that the subfloor was not done properly in some places. (We have removed about 24″ of tiling on either side of the the joint and are able to step directly on the subfloor to detect minor movement.)
The new section subfloor is plywood. Where possible, we have reinforced this floor above the crawl space so that we can detect no movement.
For some reason the contractors used OSB board for the first several feet on the existing side of the kitchen. We have reinforced this where possible from the top side (screwing into cross sections) but it is directly above the foundation wall and is inaccessible otherwise. The result is that in places we can see at most a 1/16″ flex in the subfloor within the area of a given tile when about 150 pounds of weight is place on it.
Finally, here’s my question: We plan to use about 2 feet of Ditra to bridge the joint and cover the area where there is some flex. What are the chances that we will fix the problem? Is any amount of flex acceptable? We do have a heating system and we have read carefully your advice on installing Ditra properly.
Thanks in advance for your help. We greatly appreciate it (and your humor!)
William
Hi William,
Not that much flex! Some is acceptable, like 1/480th of the span. What you have translates to more than 1/50th of the span of a given area. You will end up with cracked grout. About the only thing to do if you do not have access below is cut out that area and fill or shore it up so you don’t have noticeable flex.
Howdy Rodger, i gotta question for you. I have a large shower that is around 6 yrs old. A few years ago we developed a crack down the middle of our shower breaking every tile in its path. I saw this ditra stuff and thought, heck, instead of that cement board junk, that ditra sure looks like it would be easier. I’m ok with leaving the old tile in the shower and going right over it. The tile in it are small glass tile. We removed a bathtub and put this shower in where it sat. I used the rubber liner and then concrete over that, which is what cracked. The concrete is thick and i didnt put in enough support
. Its not moving anymore, just a crack down the middle. My thought is i’ll just go right over the tile with the ditra, is that a problem? Thanks linda
Hi Linda,
I’ll help, but you’re not gonna want to hear it.
Your shower is built completely wrong. You need to use deck mud rather than straight cement or concrete, deck mud has more sand in it and prevents cracking. It sounds like your shower liner is setting flat on the floor beneath the concrete – that leads to standing, stagnant water which will never drain. Ditra is not used for showers, Kerdi is. You can not install tile over existing glass tiles. So yes, going over the tile with ditra is a problem. The entire shower floor needs to be rebuilt properly.
Thank you for getting to my question so fast….and you’re right, thats not what i wanted to hear. I installed the floor after watching many youtubes and from information gathered from plumbers. I got so many suggestions on weep holes, so i did get the weep holes in so there is no stagnant water problems. I can take out all the floor, i just dont wanna..The ditra stuff just seemed like a great way to go over and not worry about the crack anymore.
The shower has worked great for many years, actually longer than 6. We got to thinking and i think we put it in around 2005, which isnt far from 10 years. It cracked a couple years into it.
What would happen if the ditra was used in a shower? And tiling over old tile, what is different than tilling over concrete?
Anything tile installation is only as good as the substrate beneath it. I said you can’t tile over GLASS, not that you can’t tile over tile. Concrete has open pores at a microscopic level into which concrete crystals can grow, allowing thinset to bond to the surface, glass does not. You can not bond anything to the face of that tile that will last as a substrate for any extended period of time.
You may very well have open weep holes, the problem is not that, the problem is that you have a flat surface with open weep holes in the middle of it. Water near the weep holes will drain, water flush (or actually below, if you look at my flawed page) with the weep holes WILL NOT drain. If you dump water on a completely level kitchen table and drill a hole in the center of it some water will drain out of the hole, most will not. That is what you have beneath your shower floor. Ditra has cavities in it which will hold water, more stagnant water in your shower floor. Ditra is not made for showers.
I know you don’t want to do it, and I know you don’t want to hear what I’m saying. You are attempting to put measures in place which equate to a band-aid when an arm has been cut off. It won’t work. Look on my flawed page, there is a reason I tear showers like that out every day. There is a shower floor in there which was made with straight concrete and no pre-slope – take a look at it – that is what is currently under your shower floor. You can try anything you are mentioning, it’s your shower. I’m simply telling you it is not going to work.
I know you’re right…just didnt want to hear it. Thank you
would have to come out. Most of it is tile i cut myself out of salvaged marble i dug out of the ground from a place a tile guy dumped, so its a work of art and i’d hate to lose it. Everything tiled from the ground up is perfect, its just the floor with a crack. I think i can chip out the floor leaving the walls intact, then put the new ‘deck mud’ over the existing rubber liner. I’ll assume i need to put in some sort of metal wire(i think i would have been ok if i had done to begin with) since its thick due to the drain being so high. I would think thick is better than thin anyway.
So if i take out the floor, there is rubber liner all over the floor and up the sides a good way up. Can i leave this liner if its in good shape, which it should be? If not, everything
Thank you so much for your help. I live in the middle of nowhere and have to rely on what i can find on the internet for information…Thanks again Linda
If the liner is in good shape you can keep it AS LONG AS you can remove it, install a preslope beneath it, then reinstall it. There needs to be a preslope beneath the liner. You can see how to properly build a shower floor here: Building a shower floor. The liner needs to run up three inches above the finished height of your curb, so the walls would need to be removed to that point. You can put metal lath in your floor to strengthen it, but that wouldn’t have save a straight concrete floor, it still would have cracked.
Hi I’m a licensed residential builder in Michigan. I used ditra for the very first time on a senvond story bathroom. I normally use quarter inch fiber rock with thinset underneath and screwed not nailed to sound subfloor. I was nervous to use ditra but the customer had bought it and I watched a online video. It was easy to lay cut and install. I laid a 16 in tile overtop with a beautiful centerpiece of glass mosaics in front of there 8 ft vanity. I used a sanded powder grout for the porcelain and unsanded on the centerpiece. I can email pictures. Home owners were very happy. Within two weeks give or take alot of the grout is cracking and coming out. Just the grout and only the sanded grout. I did however notice a couple tiles teeter toting in the doorway that I will be replacing. But everywhere else good shape. I have never had this happen before. I did some investigating and I think I used wrong thin set under ditra. The homeowner bought and paid for material before he hired me. But I am always trying new products so learning something on short term is a usual experience. My question is and take in consideration that the tiles are all bonded well and no movement at all besides the couple in doorway (that are most likely from walking on too soon) do you think I used too much water in grout? He didn’t purchase enough I mean barely so I think I might have thinned it out to stretch the grout(yes I know that’s a no no it was a mistake of rushing and exhaustion) or since its just a grout problem that even though I used modified thin set under the ditra(which I have no idea to this day how I overlooked) that I might have got lucky and just need to remove grout and re do with a flexible grout. And can you give me a product name of flex grout to get and or additive. I have used ditra since and have had no issues at all. I learned my lesson. But I wasn’t sure if by trying to cut a small corner and mixing some of the grout wet would commonly cause a problem like this. Thank you I hope to hear from you very soon. I have met with homeowners and they are waiting for me to resolve this issue as quickly as possible and without destroying the beautiful floor. Aplusdrywall1983@yahoo.com thank you very much
Hi Justin,
You may be able to install new grout in there, urethane would be your best option, although it isn’t ‘flexible’ in the normal sense of the word. It WILL NOT compensate for an inadequate subfloor structure, if that is the problem. I don’t know if you mistyped or what, but modified thinset is the proper type for use under ditra over wood. I can’t figure out whether or not you have backer under it or not, you only stated what you normally do.
The cracking may be due to shrinking, which would happen with too much water added to the grout. If that’s the case then regrouting should fix it, and you don’t need to use a flexible grout of any sort. If your tile is bonded properly and you have a sufficiently sturdy subfloor then that is likely the problem.
I am considering “skim-coating” over linoleum after thoroughly cleaning and scuffing the linoleum. It was glued down so well that heat, scraping etc wouldn’t get it to budge… So with clean, scuffed linoleum and modified thinset will I be good to go on the ditra???
Hi Kirk,
As long as the thinset you are using is approved for use over linoleum.
Hi:
Great article. I’m about to do a tile job and the client wants Ditra on their floor. They currently have two layers of old linoleum over plywood and diagnal lumber sub flooring. Do you think I could just put a another thin subfoor over the whole mess, then Ditra? Or, should I make the effort to rip up the old linoleum?
Thanks.
Hi Kyler,
I am ALWAYS one to remove the existing flooring first. However, if the floor is solid you can place down a layer of thinset then 1/4″ backer, then your ditra. You don’t want any wood beneath there thinner than 1/2″.
I am planning to install ditra over asbestos tiles in a laundry room. What do you use to bond the ditra to the tiles?
Hi Ernie,
I believe mapei ultraflax 3 is approved for that, but you want to call the tech line to ensure that.
We are DIY and we are putting slate 12×12 tiles on top of hearth and floor. We’ll be laying approx.20 tiles. We bought Maori modified thinset for large tiles from lowes. I read using unmodified for over the distraction, I live an hour away from lowes. Do I need to go buy different thinset for the slate tiles to the ditra?
Hi Lynn,
I assume you mean mapei, not maori? If you want schluter’s warranty then you must use unmodified. If you aren’t concerned with it use the modified, it works just fine for slate.
We have a 5×6 bathroom. Putting down 6×24 tiles. We are using Ditra on subfloor. The subfloor is only 5/8 inch thick, however has only 10 in joist. Is another layer of plywood needed??
Hi Ginger,
Maybe. A second layer of ply is always supposed to be beneath any tile installation UNLESS you are using DitraXL – the manufacturer states it can be used over a single layer of ply.