I bought a sheet of Ditra mat today to install in a mechanical room. I have a few questions about its application for those experienced with the product:
1. There are different model numbers with Ditra mat. There’s the Ditra 20, Ditra 30, etc… I wasn’t paying attention when I bought my sheet. Does it matter? Are there differences in thickness? I hope not because future installations by a tilesetter for adjacent room needs to match elevation with the small room I’m doing. I’m just installing in the mechnical room so the water heater can sit on it.
2. What exact thinset do I need to use under the Ditra product? Should it be latext, modified, etc…?
3. There is a lot of overspray from the wall texture material that landed on the concrete slab. Is there something special I need to do to the floor to remove this texture before I apply the ditra? I scraped the hard surface clean but there’s still the texture material bonded to the concrete and I’m afraid their won’t be adequate bonding between the concrete floor and the Ditra.
Thx.
Replies
I didn't know there was different models #s either so can't help there.
On thinset, you use whichever is right for the SUBSTRATE to lay the Ditra in, then use un-modified for the Ditra to tile bond. Important for you to read their instructions. If you didn't get them, you can Google them up online to print out.
I would wet scrape and rinse the overspray first. Let it dry, then go to the Ditra.
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You can Ditra 5M, Ditra 150 and Ditra 30. The number refers to the area of material in the package (5 square meters, 30 square meters; 150 square feet ). I don't know why the 150 is in square feet.
Can someone help validate the information I gathered after Googling on the topic of "what thinset I need to use UNDER the Ditra (concrete) and OVER Ditra (porcelane)?"
Modified thinset is preferred for superior bonding, but I must wait 1 week before grouting. Brands are Latticrete, Tec Full Flex, Mapei Ultra Flex2, or Custom Flexbond.
Unmodified gets the job done faster for immediate grouting after adequate bonding, and MasterBlend is the brand I can use.
I also gathered that Custom VersaBond (HomeDepot) can be used between the concrete and Ditra.
Are these sounding correct to you?
The issue with the thinset and Ditra (or any other impervious membrane) is how the thinset dries.
Unmodified thinset dries chemically, thus it can be used between the membrane and another waterproof substance, like your porcelain tile. Modified thinset, OTOH, dries by evaporation, hence the recommendation you found to wait a week before grouting. BTW, I have never heard that specific recommendation until now; previously Shluter's position has been that if you use modified thinset with Ditra that invalidates the warrantee.
That said, I know a number of people (me included) who have inadvertently or deliberately used latex-modified thinset successfully with Ditra. But it's not recommended.
Of the brands you mentioned I am familiar with TEC (FullFlex), Mapeii, and Versabond. One is about as good as another in my experience. One thing you do not want to use is a new crapola product on the market called 'premixed thinset'. It is not thinset mortar at all, but is a mastic with sand in it. There's no cement.
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
One thing you do not want to use is a new crapola product on the market called 'premixed thinset'. It is not thinset mortar at all, but is a mastic with sand in it. There's no cement.
Dino
I don't want to hijack this thread but its a related Q so here goes;
I'm doing a side job, small bathroom remodel and the HO'ers have their own tile guy - friend of the family or some such. Tile guys say that they are going to use the Kerdi system and I'm sorta glad as I want to do some new bathroom remodels in my new/old house so I figure I'll get an up close and in-person tutorial!
I have some vague idea of how the Kerdi is supposed to be done but always figure I can learn some new stuff from the pros. This may be where I run into a problem - these guys may be charging for their work but PRO may be a stretch.
These guys are using that stuff that you refer to, premixed thinset, they installed some bullnose tile where they had to build up the thinset(maybe 1/2") and after 48 - 54 hours the stuff was still soft underneath. The way that I know that is one of the bull nose tiles fell from overhead and broke a few of the tiles on the curb of the shower.
I let them know about it and their grout guy came out to see what the problem was. He explained to me that because of the Kerdi the thinset took much longer to cure due to the fact that the moisture could not escape, Kerdi being water proof it took much longer for it to set up. My thought going through my head was that I was talking to a used car salesman but figured that the job aint mine so ..........
Also they installed some sort of sheetrock like stuff on the walls and said that because they are using that stuff they didn't need to run the Kerdi up the walls. This stuff they were using was supposed to be water proof! They told me that all they had to do was run the Kerdi tape on the joints and then they could tile away. I snapped some pictures of their work. They didn't run the Kerdi on the joints - they just thinseted them. Here is where I think they actually did use real thinset but to lay the tile they were using the stuff out of the bucket(premixed thinset)
First picture is where the old sheetrock IN the shower has had nothing done with it. It is adjacent to the new stuff that they installed(the sheetrock like stuff) As you can see they havnt done anything to the corners/joints. You can see the remnants of their premixed thinset.
View Image
This next pic shows how they detailed out the joints, just applied a coat of thinset(the real stuff) but there is no Kerdi tape on the joints!
View Image
Another way they detailed the joints!
View Image
The whole job looks suspect to me but what the hell do I know! I assume that I will need to find someone else to learn from. ;)
Doug
Edited 9/14/2007 8:49 pm ET by DougU
If my eyes and your photos aren't deceiving me, that is pretty appalling work for a shower.....that is a shower they're tiling?
Wow! Should be an equal opportunity leaker, though (leaks equally at all corners and between the tiles).
Last year I was building a couple of large custom showers and ran shy of thinset to finish a few last pieces. Jumped in the boat, crossed the lake, jumped in the truck, drove to a little building supply that doesn't have much but I was trying to avoid a 30 mile round trip to the tile supply.
Ah Ha! The little store had a small bucket of that premixed stuff!
Returned to the job, glued the last tiles to the wall, cleaned up and went home. returned the next morning, those last pieces were laying on the floor and the premixed thinset was still soft.
Lesson learned!
If my eyes and your photos aren't deceiving me, that is pretty appalling work for a shower.....that is a shower they're tiling?
Yea, thats a shower!
I dont know how long it will last but what the hell are you supposed to do - its family!
Doug
They used Denshied, a good product in my opinion when used and detailed carefully.
Like using epoxy coated screws. Looks like they used roofies.
Fiba tape and thinset the joints and cover the screws too while your at it. Better to Kerdi Band the joints.
Pigs those guys. Complete hacks.[email protected]
Looks like they used roofies.
Yes, roofies.
They cant be worth a shid on their own can they? I assume moisture will start to rust them at some point, especially since they are just the electro plated ones.
Is it common to tape the nail, or screws just as you would when you do drywall work?
They told me that they were going to run Kerdi tape on the joints, even said that they only had to go 6' high because that's all that was required, but they didn't. I looked real close and there is no way in hell there is any tape under that thinset.
Doug
Edited 9/14/2007 9:36 pm ET by DougU
Well, if you are going to get screwed, might as well keep it in the family
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might as well keep it in the family
When the shower leaks, and it seams like it will, it might be uncomfortable around the Christmas dinner table though!
I'm just glad I dont have my name on any of this shower! I would like to tell them but I dont know how, and who the hell am I to tell them that their BIL is a hack!
I did say something to one of the tile guys about using the premixed thinset and that I was concerned about it setting up, or the lack of it due to not getting any air. I think thats why they let it sit for a week before grouting though, dont want any of the tiles to fall and smash the HO's toes!
Doug
That is terrible. The kerdi is completely waterproof, but who cares since the corners will leak like crazy and get behind and under the kerdi pan. Something like that is sad though, people like those customers are probably good people who are trusting. Now they are going to find out they were screwed.I did a kerdi shower and aside from a little bit of a learning curve, it is pretty easy. The main thing is getting the kerdi up on the walls or where ever as fast as you can. I was a bit ambitious and tried to do too large an area and had the thinset drying on me a bit. I look at it as to be in the best situation, you should just kerdi everything in the shower, floor, walls and ceiling (if enclosed).Also, that thinset must be ####. I'ved use kerdi and Ditra and with both you use unmodified on the top and with small or large tiles, the thinset was hard overnight. Also, with tiles on the ceiling applied to kerdi, there was no problem at all. Once you put it in place, the suction was so strong it was difficult to remove if you wanted to. Get the Kerdi/Ditra cd from schulter for them, they need to understand the product before they use it.
Get the Kerdi/Ditra cd from schulter for them, they need to understand the product before they use it.
That's funny because I was talking to one of the tile guys about the Kerdi pan and such and he took the CD out of the box and handed it to me, said that everything I need to know about it was on there, Braged about how simple it was, well I guess so seeings how you cut out several of the steps!!!
Maybe I should give it back to him after I watch it, seams that he needs a refresher course.
Doug
The area where the wall meets the pan, the kerdi looks like it is fine, don't know about the drain area, that is simple but who knows with these folks.The video shows how to set the presloped pan, then kerdi the pan, corners, etc. then it shows the wall. The one in the video is an open ceiling shower and they go up at least 6 or 7 feet. The kerdi for the walls in that picture would not have cost much, I think it figures to $1/ft and basically goes on like wall paper. For around $100 they could have had a nice shower, now they are wasting all that money on tile, nevermind fixes the damage from the leaks. If they are lucky, it will leak enough right away.
D
I saw them put the pan down and they seamed to do everything as the instructions show but when they got to the wall I think they decided that the sheetrock like material( I forgot what it is called) was sufficiant. I couldnt see how nailing it with roofing nails could be good unless you somehow did something to seal them, not to mention leaving the joints with no tape. I cant hardly think the joints with nothing more then thinset will eventually crack and fail.
Looks to me like they do this and save the Kerdi material(they did have several rolls of the stuff) that way they can do three or four showers by buying two or three systems/packages!
Doug
use the modified UNDER the Ditra for most substrates, but always use unmodified over the Ditra.Default position when unsure is use unmodified, IMO.Either CAN work, but the modified can take forever to set up with large tiles where no air gets to it. The unmodified is like portland cement - it does not dry - it cures chemically as Dino said. The modified is slightly stickier for hard impervious surfaces, like if your concrete finish is very smooth and has been sealed. Modified can also make for a slightly more forgiving, modestly flexible bond for different materials like plywood base instead of CMU board.If your crete surface is hard and smooth and you want to use unmodified under the Ditra, you could scarify it first.
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What then is the "logic" one applies when using modified or unmodified thinset? is it dependent on the type of material to be bonded only or is there rules of thumb for their uses?
It varies by type of material being used. you can read the bag for indications which products a thinset is best for and sometimes a type of tile will state clearly which type of thinset is best to use with it.IMO, either will work for any, BUT there is generally a best for any situation.
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Here's the logic. If the thinset can dry easily (such as under the Ditra) you can use modified or unmodified thinset. If the thinset cannot dry easily (such as when setting large porcelain tile over Ditra) then use unmodified.
Remember that unmodified thinset is (like) cement -- it sets like regular cement by chemical reaction. It does not need to dry -- in fact concrete will "set" when underwater.
Modified thinset (modified with latex) must dry to set. If you use it between Ditra (which is impermeable) and porcelain tile (which is also impermeable) then the only way it can dry is through the grout lines, and this can take a long time. That's why you should use unmodified thinset in this application.
Billy
Wow! Pif the tile chemist! I'm impressed.
I would recommend unmodified under Ditra, applied in globs at 16" centers, but never at 24".
You been drinking alreaady tonight, Gene?
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I attended Schluter School this week at CTEF in Anderson SC as a guest of John Bridge Tile Forums. It was great to meet FH contributor Tom Meehan.
What Piffin and Dino said is correct.
Below Ditra: Unmodified on a slab, Modified on a plywood subfloor.
Above Ditra: Unmodified or dryset.
Have you checked the deflection of your floor system? If you really want to know about Tile/Stone installations here is a link.
http://www.johnbridge.com/vbulletin/index.php
Chuck S
live, work, build, ...better with wood
Edit: spelling
Edited 9/14/2007 9:40 pm ET by stevent1
I think he is on a slab, so deflection should be minimal, LOL
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"I attended Schluter School this week at CTEF in Anderson SC as a guest of John Bridge Tile Forums. It was great to meet FH contributor Tom Meehan."
I thot I read that John himself has switched to modified top and bottom?
could be wrong ... so don't quote me here ... I'll try to check it out for myself and suggest U do the same.
I prefer modified top and bottom ... as long as the job can wait a coupla days and have more time to dry out. Haven't had a problem on jobs I did when ditra first hit the area and I didn't know better ... but now I try to give it more time between setting and grouting.
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
I have seen a couple of people over at John Bridges talk about LIGHTLY modified.Don't know how you judge the amount of "modifications"..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I used to get a thinset that was unmodified, but if you bought the right liquid to mix it with, it became modified. Use water and it was unmodified, Forget the name.
But I think it was permissible to add half water and half modifier liquid instead of all the liquid.
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BTW, I don't remember liking it half and half. Kind of mealy to work with and slow to set.
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I just used some Ditra a few weeks ago and used Kerabond thinset, which is unmodified and you just add water to keep it that way. If you want modified, you add Keralastic instead of water. One jug of the keralastic to one bag of thinset is the normal mix, although I guess you could use less. The Keralastic looks basically like milk.
Before the days of dry latex additive (not so long ago; less than 20 years) if you wanted 'modified' thinset you bought a jug of 'milk' (latex additive) and mixed it into the thinset powder instead of water. This was standard procedure at that time as there was no such animal as ready-modified thinset powder.
One thing I've always wanted to ask a real mason (who oughta know if anybody should) is if you can just add a bit of lime to unmodified thinset to 'fatten' it a bit so it's easier to work with (stickier). I know this is done for brick mortar.
If this is a workable idea for thinset, how much lime would be appropriate for how much thinset mortar mix?
Anybody?
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
I do think that used to be done.With that thread I had up last winter about the antique Moroccan tiles I was asked to use, I had to use grinder and wire brush to remove the old mortar is was set in. That was a very high lime content.I would not consider this to be any kind of ideal solution in wet locations though, like showers, or floors regularly wet mopped like restaurant kitchens, because of the way lime will rework and bleed.
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Okay, now you're teaching me something I didn't know: that lime content in mortar could rework under wet conditions. Would that be the cause of efflourescence in brickwork?
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
Yes.Lime in the mortar will move as water passes through. old chimneys and soft brick exteriors built with lime mortar are recognized as self-healing, because the lime will leach and reconstitute itself in those small cracks and crevices.But the down side is that over time, the lime will leach away.here on the island most of the old summer places were built on piers that were done so -
They dug a deep old hole in the ground, and rolled in bolders and stone with lime based mortar burned out right here on island with washed beach sand. Then as the pier got to the ground level, they switched to bricks for the 18" to eight feet that needed to be visible. After a hundred years, anything that was below ground level would have the lime washed out, whether stone or brickwork. We get a lot of water in out soils here moving through. I have replaced a LOT of these foundations. Same thing with the solid wall rubble stone foundations. They would get patched sometime after oh, about 1959 with portland based pointing up above ground and on the interior of the cellar, but when we dig to add-on or replace foundations, all the mortar between stones has turned to sand because the lime has washed away.The lime in mortar makes it more workable, but the portland makes a better chemical bond between materials and aggregate
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Oh, boy, you don't know what you did to my afternoon with that answer!
I just spent the last three or so hours reading everything I could find on the differences between lime and portland cements, how each is made and what of, different types of lime kilns and cement mills, carbonation, pozzolans, hydraulic and non-hydraulic lime mortar, hydrated lime and lime putty, cement chemistry, mortar-mix designs....
TABLE 3 - ASTM C270 Proportion Specification
Mortar Type
Proportions by volume (cementitious materials)
Aggregate Ratio - Measured in damp, loose conditions
Cement
Lime
M
1
¼
Not less than 2¼ and not more than 3 times the sum of the separate volumes of cementitious materials
S
1
Over ¼ to ½
N
1
Over ½ to 1¼
O
1
Over 1¼ to 2½
And now I'm freezing and hungry and the office is still a mess and I haven't paid the bills or made my bread for next week yet. And I was gonna make a batch of pork-n-beans, too....
But I can surely drive the idiots at the big box nutz next week. 'Uh, I need a 30kg bag of pozzolan.'
Thanks, Dean Piffin.
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
Edited 9/16/2007 5:51 pm ET by Dinosaur
Thanks to you friend.Did you notice that special mixes are recommended for historic preservation?There goes your evening...
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And more researchBut what is the detailed differences between mortor and thinset..
.
A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Okay, let's have a fair division of labour here; YOU research that one! I'm hungry!!
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
I could be wrong, but in my mind, it is mostly finer grading of aggregate
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