Effects of Improper Ditra Installation

by Roger

Improper coverage on tile / Ditra not filled correctly

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 :D ) 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)

Improper coverage on tile / Ditra not filled correctly

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. :D

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).

Improper substrate for Ditra

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. :guedo:

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.

Improper substrate for Ditra

Photo 4

Most any plywood (even osb :whistle: ) 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 8)

Previous post:

Next post:

loti

Dear floor elf,
we are almost finished installing ditra across 750 sq ft, the space includes kitchen, living room, dining area. We laid out the ditra to have as few seams as possible so we have 5 continuos lengths which are notched in places to accomodate closets and short walls We tore out old tile, and carpeting, filled in holes in the concrete, and sanded down high spots. To the ditra installation, the night before the concrete was mopped with water only to get rid of dust, as well as vacuumed. The day of the install we pre moistened the concrete before trowelIng the thin set the thin set was different consistencies from runner to thicker but all held a “v”. After we ran through the two 50 lb bags of plain thin set from the tile distributor we bought Custom brand non modified from HD. There are areas that look like they’re not sticking, it hasn’t been 24 hours yet but if we see that there are intermittent areas where it’s lifting, can we slice through the Ditra and just repair those areas (are seams an issue?, or do we have to roll up the entire length and scrape up the thin set and reapply?) Can we even reuse the Ditra once it’s pulled up? One thing is for sure, we are taking a break for a week before going forward. I’d much rather deal with the issue now, then after the tile is down.

Also when we are ready to I stall tile should the thin set be running runner for the top of the Ditra installation?
thank you in advance for your help

Here is what it looks like now, once we’re back in the house I’ll send pics of the Lifted areas

https://flic.kr/p/r7ECm3

Reply

Roger

Hi Loti,

You can cut and patch ditra wherever you need to. It is normally just an issue when the fleece on the bottom is not embedded, that could be because the thinset skimmed over before it got covered or simply not pressing down enough to embed it well. If, when you cut it out, the fleece does not tear off of the back you can reuse it. If the fleece tears off the back – it was fine, you shouldn’t have ripped it up. :D Make sure it’s actually lifting off the floor before cutting it out.

Mix your thinset normally for the tile installation, not runnier.

Reply

brad

Can I lay 1/8 ditra right over 3/4 plank pine boards for underlayment?

Reply

Roger

Hi Brad,

No, you need a 1/2″ layer of plywood over the planks.

Reply

Ann

Dear Roger,
I’m sorry for responding in the wrong place on your website, but I’ve pasted this question several times, and haven’t heard back from you. I’m not certain what I’m doing wrong. Hopefully, I’m better at tile than technology : ) Anyway, my question is listed below….

We are doing our umpteenth tile installation. Or, at least it seems that way. Our oldest son was over last night, and, as usual, was giving advice to us on what we are doing WRONG on our tile installation plans. Since there is at least a small chance he is correct, I thought I’d ask your opinion.

We are planning to put 21″ x 21″ tiles in our basement bathroom floor. They are very high quality, textured-type commercial tiles. He stated that tiles installed on concrete will always, always crack, and that we should go with smaller tiles to prevent this. (He worked at one time for a “high-end” remodeler, so he has some experience in these matters.)

Our first thought is that if the tiles are installed correctly, with actual thin-set under the entire tile, it shouldn’t crack. But, what do we know? We’re just the old, feeble-minded parents. Should we play it safe and put Ditra over the concrete and under the tile? Go with smaller tiles? Give up and use carpeting?

We couldn’t have done the tile projects we’ve already finished without you….many thanks,
Ann

Reply

Roger

Hi Ann,

There is no ‘wrong place’ on my website. But I did respond to one of your posts (the others were deleted) five days ago right HERE. I get all the questions, and answer them. You should have received an email notifying you that I answered it, it’s likely in your spam folder. The only thing you’re doing wrong is repeatedly posting the same question. Stop that. :D

Reply

matt

Hi roger,
I have done many tile jobs, but trying dit ra for the first time. A friend of mine suggests I fill the cavaties, let cure 24 hours then notch and lay tile. He is an experienced tiler specifically with ditra and I’m not doubting his word lol but I have not seen or heard anybody suggest this via how to videos etc… have you ever heard of this method? And what are your thoughts?

Reply

Roger

Hi Matt,

Yes, I prefill ditra often. And no, you won’t find the method stated online. :D It works just fine.

Reply

Ann

Roger,
Just installed a porcelain tile floor in a heavily traveled room with the long tiles that look like wood. I had a wood substrate, used modified mortar, then the ditra (not XL). Waited 24 hours and put unmodified mortar AND thought I covered all the little squares going several directions with the trowel. Here’s the issues. This was my first ‘big’ tile job as I’ve usually just done little back splashes, and they seemed easy and ‘stuck’ so thought I’d give this a try. (Too old to have even contemplated this task, but alas,… here I am) Obviously I didn’t understand the value of a trowel and the benefits of the sizes. I put too much modified mortar under the ditra in the beginning so lessened as I went. Noticed occasional ‘hump’ in the ditra. And appears it may have happened in other spots. Getting ready to do grout tomorrow (time line for furniture to be back in room), and after 24 hours of tile being on floor found one that evidently didn’t stick. Right in the middle of the floor where traffic will be of course. So I’ve scraped all the old mortar out and redid it with extra mortar because I’ve noticed there were some spots without mortar showing on the tile. Now I’m near panicked how many more may break loose?? I’ve walked all over it listening for any sound of giving. Tried the tapping for dull sounds and occasionally I hear it, but not sure as tile ‘seems’ set and became a daunting task. I can’t find anywhere online about too much mortar under the ditra causing uneven floor, (I definitely have some lips but conceding on those as not the worse thing). Question is: If others were like this one, would they have come up by now with me walking all over them and scraping the edges for grout? And, IF worse comes to worse and they break or lift, could should I cut through ditra to modified mortar and build back in layers?

Reply

Roger

Hi Ann,

It may very well happen to only one tile in an installation. If everything else seems solid go ahead and finish it. If another does happen to come up, cut all the way through the ditra and reinstall in layers as you’ve stated.

Reply

ron

thanks nick I didn’t know that guess i’ll have to read a little more….ron

Reply

Roger

Please use the ‘reply’ link when replying to someone, something clearly stated above the box in which you typed this. I have over 30,000 comments here (seriously), when the reply link isn’t used they are not threaded (one following the comment thus making it a ‘reply’) and it looks like random people talking to themselves.

I’m the only one allowed to do that here! :D

Reply

Nick

Hey Ron,
I am not a pro but I read the Ditra installation manual on the schluter site because I too am using it…and I think 2×2 is the smallest you can apply to Ditra.
Fyi …and sorry if I am hijacking.

Reply

Roger

Hi Nick,

I have no problem with hijacking with correct information – and yours is, thank you. It is more effective, however, if you use the ‘reply’ link in the comment, that way the author of the comment gets a notification emailed directly to them. Thanks for your help, I’ll take all I can get! :D

Reply

ron

hi roger,
im installing 1×1’s over my ditra floor is it necessary to back butter them., and should I do the same for the rest of the bathroom…all the tiles are 1×1’s in a mosaic pattern
thanks ron

Reply

Roger

Hi Ron,

No, 1×1 mosaics do not require backbuttering. However, 2×2 is the smallest tile you should install over ditra.

Reply

Leave a Comment

;) :wtf: :wink: :whistle: :twisted: :suspect: :shades: :roll: :rockon: :oops: :lol: :lol2: :lol1: :idea: :guedo: :evilb: :evil: :eek: :dance: :cry: :corn: :cool: :censored: :bonk: :arrow: :D :?: :-| :-o :-P :-D :-? :) :( :!: 8)