Bathtub installation -- order of installation (end pony wall, tub, heated floor)?

Discussion in 'Shower & bathtub Forum & Blog' started by jch, Jul 10, 2011.

  1. johnfrwhipple

    johnfrwhipple I love these ACO Shower Drains - Best in Class

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    John are you serious! Unbelievable. And people wonder why I have so many issues with Schluter.

    Good on them for replacing the Ditra but ask Schluter for a better water ratio mix. The boys and techs from Mapei are not going to tell you to over water their thin set so you will need Schluter's help on this.

    As for the best way of removing the old thin set try placing a wet rag over a section for an hour and then using your scraper. Before you layed the Ditra was there any places at all the cable heat was proud of the finished floor height?

    How much thin-set did you spread when you layed the Ditra?

    Is the floor heat on or off? Off is the correct answer.

    Your bonding issue and the over watering of thinset is one of the reasons we don't use heating mats or heating blankets. I have heard of similar failures with the bonding issue.

    I feel for you John. Sorry to hear that. Thank God you found it before you layed all the tile....

    It might be a good idea to lay the next round of Ditra down in smaller sections - say 3'x3' squares.

    Did you roll the Ditra? Did you walk on top of it while installing? How strong are you? How much do you weigh?

    When installing Ditra, Kerdi, Tile, Noble, Wedi and anything that requires thin-set remember that you need to check the coverage rates. Lift up the Ditra and check the coverage, then re-set it.

    JW
    Last edited: Jun 30, 2012
  2. jch

    jch New Member

    Yes it was good of them to replace the Ditra, although there's no way I was going to shell out for a replacement when I was following the thinset manufacturer's directions... I would've switched to a competitor's product.

    Schluter said to add water to the Kerabond until it's like yogurt--will hold ridges but they'll slump. When I said that Mapei says not to overwater it, they said it's not overwatering--it's just being at the top end of the water range...(!)

    When laying the Ditra the first time, I pulled up the Ditra and it had full coverage stuck to the underside. The pattern on the thinset now on the floor confirms that I had full coverage (no trowel lines), but I suppose it wasn't wet enough to actually soak through the weave of the fleece.

    I used the official Ditra 4.5mm square trowel.

    Floor heat has never been on.

    I used a float to embed the Ditra in the thinset. There is a very strong grid impression in the thinset, so mechanically I think I did everything according to Schluter's instructions. The problem seems to be that stock Kerabond won't wet Ditra's fleece enough for a strong (and quiet) bond.

    I'll try the soaking methods for getting the old thinset up. My Novaplan Easy SLC is grey (covering the heating wires) whereas the Kerabond is white, so it should be easy to tell how far to scrape.

    Interestingly, the hairline cracks in the SLC have *not* telegraphed through the thinset... Maybe I don't need an anti-fracture membrane after all ;-)
  3. johnfrwhipple

    johnfrwhipple I love these ACO Shower Drains - Best in Class

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    3,816
    Location:
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    I wish you lived in North Van. I would hit you up for a case of beer and we could bang this floor out in an hour or two!

    I helped Dave Randal from Mapei build his son's shower here in North Vancouver. We worked on it a couple of days but Dave did all the work - I just helped with the linear drain install. One thing that impressed me the most about Dave was the care he took in measuring the water content. He measured exactly and told me that these thin-sets, concrete repair products and grouts are "Exact Science" the water range is all you have to work with.

    When you over water concrete you weaken it. The art here is finding the happy medium between overwatering and strong enough and water properly and no bond with the Ditra. It bothers me that this information is not made available from Schluter. Why can they not specify the water mix?

    Perhaps switch to a 1/4" by 1/4" trowel for the next install. Get the Ditra set, stand on it and slide back and forth - this will be too much thin set but straight away you can left up the Ditra and then re-comb it with the proper trowel.

    Or screw Schluter and there warranty and use Grani Rapid from Mapei.

    Or call on Ardex and ask for a thinset recommendation for Ditra with a friendlier water ratio.

    Or use some stucco mesh and call it a day.

    Or, swing by my place for some Noble Seal TS - It is harder installing Noble Seal TS than Ditra though.

    Your so close. I don't doubt for a minute that this stage will get the best of you. Push on man. We are waiting for finished pictures...

    JW
  4. dlarrivee

    dlarrivee New Member

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    1,172
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    Mapelastic CI?
  5. jch

    jch New Member

    Picture time...

    This is what the thinset looked like when I set the first 2/3 of the Ditra. Notice that it holds notches:
    IMG_4139_small.jpg

    and the first 2/3 down:
    IMG_4141_small3.jpg


    2 days later, there was a crackling/pop-rock sound when stepping on the Ditra or when rocking back and forth on a 12x24" tile laid on top of it. Schluter told me to cut out a square of Ditra and try to peel it up. They were hoping that the fleece would rip off the back of the orange plastic. Unfortunately, that was not the case. Notice how the coverage is quite good:
    IMG_4143_small.jpg

    After peeling all the Ditra up (and stretching/ruining it in the process). The new Ditra is on the left. The pulled-up Ditra is on the right. Notice how coverage on the floor is good and that the grid pattern is very prominent from pressing the Ditra into the thinset.
    IMG_4145_small2.jpg
  6. johnfrwhipple

    johnfrwhipple I love these ACO Shower Drains - Best in Class

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    Location:
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    John that is not going to work.

    When you pull back the Ditra it needs to have the thin-set squished into the fibers of the fleece. It is hard to spread it all out, line up your trowel lines and lay without the thin-set skimming over. Better to place a wack of it on the floor, flat trowel or burn it in and then let it dwell while you do this. Then scratch your trowel lines while you roll the ditra into posiiton.

    I've seen so many 'Pros' mixed their setting material so they can pour it out of the bucket. I do not like this approach but it's easier - not better - easier.

    Is there a bond breaker on the back side of the Ditra? Did it get dusty?

    Try a sample piece like I mentioned above. See if you get a good coverage rate. I'll bring in some Ditra to work today and show you a coverage check on some scrap drywall.

    Work on prepping the floor and do another test. Use an off cut and some scrap cement board or drywall to get a feel for it.

    Working in smaller sections might help you get the product down faster.

    JW
  7. jch

    jch New Member

    I tried wetting some of the old thinset--it makes it less dusty to scrape, but is really thirsty.

    Now I'm wondering whether it would help next time to mist the hardened thinset, trowel on new thinset, then mist the back of the Ditra before rolling it out.

    Would a damp fleece help the thinset bond better??
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The fleece bond strength is around 75#, the 'perfect' thinset is around 250-300#/sqin. Overwatering it enough to embed the material won't hurt with any similar membrane but it can't be soup. Now, on top of it, to a tile, it is MUCH more critical to get a good mixture. The membrane to tile bond should be max, if possible even though the membrane would release first you want full coverage and a good bond to the tile. The dovetails will lock it into the membrane if filled properly. There, the consistency of the mortar needs both bond strength and compressive strength for best effect.
  9. johnfrwhipple

    johnfrwhipple I love these ACO Shower Drains - Best in Class

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    John I got nothing for you. I have not tried to do this before.

    When you installed the first round of Ditra how long did it take you to set it inplace? Was there a draft or anything that could have made the thinset skim over?

    If Schluter and Mapei won't recommend a water mix why not ask Jim. Jim should John overwater his thin-set by 10%, 20%.

    It is truly amazing the effect an extra handfull of water has on a five gallon bucket of water. Maybe try 5% added water and do a test run. Perhaps set one 3'x3' square and then start the tile in the tub surround. This should give you a few days to see the effects of this added water mix.

    I never got to that test sample for you John but I will try and find a good picture showing the coverage.

    So few examples online of checking for coverage on the back side. I thought I would find more references but did not. http://www.go-tile.com/advice_ditra_matting.php This link has a good picture of the proccess but not so close up you can see the floor.

    [​IMG]
    http://www.facebook.com/photo.php?f...9990817.118951.258556230836606&type=1&theater

    If you look at this picture you will see the floor coverage and the little spikes it makes when the membrane is lifted off the floor.

    Checking for coverage when tiling is key as well.

    JW




    JW
    Last edited: Jul 1, 2012
  10. jch

    jch New Member

    I had full coverage on the back side of the fleece when I tested it, but it wasn't spiky like that! So definitely need to go with at least some more water in the mix.

    Question: The first layer of Kerabond thinset is so firmly attached to the SLC that I can't get it up with a scraper. So I've used the scraper until it's smooth and as close to level as I can get.

    Do I need to *mist* this existing layer of thinset before I apply the next layer?? I'm concerned that it'll suck all the moisture out of the new thinset.

    btw, there were no drafts/sunshine when I put down the Ditra originally. There was less than a minute between applying the thinset, trowelling, and rolling down the Ditra -- very fast -- so I don't think it could have skinned over. The whole room took less than 20 minutes, applying thinset as I went.
  11. johnfrwhipple

    johnfrwhipple I love these ACO Shower Drains - Best in Class

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    John I'm not a mister. I like to use a sponge with clean water and clean the surface. Make sure you vacumm well and then wipe it down with a sponge. You can't soak the floor or the water will further weaken the thin-set. We like to load up the section we will be installing with thinset and burn it in. Then just before laying the Ditra comb your ridges. I walk on my installs straight off and then switch to my roller or 2"x4". Lift a corner, check your coverage and once OK'd move to the next section.

    Once layed we try to not walk on the fresh Ditra until the next day. And even then we often lay out scrap boards to walk on. Do not vaccum your Ditra install for a couple of days since you can pull it up.

    JW
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The best and only real way to tell is to apply some, install the membrane and see if it is getting properly embedded. Once you do this a few times, you'll recognize when you have the proper mix. It might take as little as a half-cup - it might take more or less. It can't be soup, and as said, it must be properly mixed with a decent paddle at the prescribed rpm. Excess air entrainment IS a problem. I don't remember the max value, but think it was in the order of 10%. It's easy to get MUCH higher values if your drill motor is too fast or the paddle isn't optimal. And, because on smaller batches, a large paddle may not be entirely submerged, you will get more air entrainment than if it is fully covered.

    Also note that, while it doen't happen all that much, if you mix a partial bag, you might be getting different results depending on how it was mixed at the factory and how it was shipped. Things can settle, and there's no guarantee the top of the bag has the same mix as the bottom, only that you have the right proportions of ingredients in the whole bag. My projects have always taken me too long to use a whole bag at once, either from the complexity of things or the smaller areas. This means that I'm mixing partial bags of thinset almost all of the time. I tend to use a bathroom scale good to around 0.1#, and calculate the water accordingly. That gives a good starting point.
  13. jch

    jch New Member

    Yah, I've been doing the bathroom scale and measuring cup thing too...

    After cutting the replacement Ditra to shape, I decided to take a break today and instead mixed up some Synko Concrete Fill ("con-fill" as the contractors here like to call it) with my new egg beater paddle. Con-fill has got lots of fibres in it (for strength) and is great for filling holes/gaps up to 1" in concrete board (HardieBacker in my case) and for bringing crooked pieces back into plane with each other. It doesn't shrink and is rock hard in an hour -- great stuff!

    Next up I'll tape the seams on the HardieBacker with alkali-resistant fibreglass tape and embed it in some thinset.

    After that's all done, I'll return to the floor and the Ditra.

    Gotta say this egg beater paddle traps a lot less air than the double-box one did -- probably because it's only 5" in diameter, instead of 8" -- a big difference in speed when the drill can only go at 600 rpm.
  14. johnfrwhipple

    johnfrwhipple I love these ACO Shower Drains - Best in Class

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    Concrete Fill is used for drywall not tiling. I have never used it on a backer board install.

    Why did you not just use thin-set?

    1" holes in your backerboard?

    Oh man. We better look at this....


    JW
  15. jch

    jch New Member

    Thinset shrinks too much. I've got a lot of sharp angled corners (slanted ceiling) that don't work well with the "score and snap" approach to trimming HardieBacker. And trying to trim 1/2" off the edge of that stuff leaves a pretty ratty edge. Con-fill fixes it in one coat. You should try it -- works great.

    edit: see 2 posts down from here....
    Last edited: Jul 3, 2012
  16. dlarrivee

    dlarrivee New Member

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    Stupid question, why are you doing the floor before finishing the drywall?

    Who recommended a setting type joint compound (reinforced or not), for your cement based tile backer?
  17. jch

    jch New Member

    1) Because I thought it would be easier for me to tile a floor than a sloped ceiling--start with the easier part first then do the other. Also in no big hurry so could let the floor cure before moving on to the walls. That said, I'm now focusing on the walls/ceiling and will resume the floor once the walls are taped.

    2) A contractor friend recommended con-fill for fixing spots where the HardieBacker had not snapped cleanly (corners etc.). From the name, I was assuming that it was primarily cementicious. However, having used it now, I see that it is plaster of Paris based, with some cement in it.

    This could be a big disaster when I apply thinset over it--it could soften.... Now I'm hoping that the layer of AquaDefence will make this a non-issue when I'm installing the tiles. However, during the taping phase it could still be a problem. We'll see.

    So much advice, so much to learn.... Appreciate all the help.
  18. johnfrwhipple

    johnfrwhipple I love these ACO Shower Drains - Best in Class

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    John - I'm glad your still plugging away at this and sharing your progress.

    Cement Fill rocks up hard but really is not a proper backer material - that said if you can achieve 80% contact on sound backer board you will be alright. AquaDefence does stick and dry to cement fill. Once the Aqua Defence dries it will not reactivate the cement fill and make it mushy.

    To add strength to these areas do you have any stucco mesh?

    JW
  19. jch

    jch New Member

    No mesh -- there are only a couple of spots inside the wet area that I used it -- to fill in broken off edge chunks of HardieBacker (1/4" x 3/4") and along the top edge of the shower head wall (where it meets the ceiling).

    I extended HardieBacker into the dry part of the room (long story) so there I used the con-fill to skim areas that weren't perfectly in plane with each other and to fill some gaps where it met a non-true existing wall. None of these dry areas will be tiled so thinset compatibility is not an issue there.

    We'll see how it stands up when I'm taping with thinset... Worst case it'll turn to goo and fall out, in which case I'll just replace with a few applications of thinset.

    Still nice stuff to work with though :)
  20. johnfrwhipple

    johnfrwhipple I love these ACO Shower Drains - Best in Class

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    3,816
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    I'm a fan of the cement fill myself John.

    If you have some Aqua Defence you might try giving the cement fill a coat before thin setting. Nothing sticks to drywall compound that well. I have been trying different primers over drywall for some time looking for a good solution and have found that the Planicrete AC cut with water works well. The Grani Rapid liquid cut with water - not so well. I have some Mapei Prim Grip we are testing out as we speak.

    I would imagine that any left over self levelling primer cut with water might work for a small patch repair. If you mock it up before hand I bet you find you get a better bite with both Aquadefence or thin set once these areas are primed.

    Lets see some more action shots. I like pictures!

    JW
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