Any professional tilesetters in here - Ditra Mortar Coverge

Discussion in 'Remodel Forum & Blog' started by chefwong, Nov 17, 2011.

  1. chefwong

    chefwong New Member

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    How accurate is this per their handbook:


    To bond DITRA to the substrate: Use one 50-lb. (22.68 kg) bag of mortar per 150 - 200 sq ft (13.9 - 18.6 sq m).
    To bond the tile to the DITRA: Using a 1/4" x 3/8" (6 mm x 10 mm) square- or U-notched trowel will require 50-lb (22.68 kg) bag of mortar per 40 - 50 sq ft (3.7 - 4.6 sq m)


    I'm ~traveling~ to pick up Kerabond and having extra bags (returns) is not exactly a option with the supplier.
    I'd like to be on target for real world usage on the amount of mortar used for Ditra (application, waffle filling, tile)
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    The bonding to the substrate is fairly consistent. Note that the type of thinset you use depends on what the subflooring is: if it's a wooden subfloor, it must be a modified thinset, otherwise, it can be an unmodified...they are quite specific in their installation manual and it behooves you to follow it for best results.

    The top, setting tile, is more problematic. The more irregular the subfloor or inconsistencies in the tile will call for more thinset to ensure that you get a nice flat tile installation. And, they specify this thinset must be an unmodified variety. So, you may need two different varieties, or an unmodified with an approved, add-in modifier, or separate varieties.

    How fast you work, and how much wastage you have from maybe not using all of the thinset prior to it starting to set up may also have an effect on your coverage. Also, how you hold the trowel can make a big difference in the actual thickness of the applied thinset. Hold it at 90-degrees will use more than holding it at say 45-degrees. So, estimates are just that.

    In the scheme of things, the stuff isn't all that expensive...depending on what your time is worth, having an extra bag or two probably shouldn't be a deal breaker. Also note, the stuff you buy will have a manufacturing date code on it, or a use by date. It does potentially go bad - you don't want it to be close to the use by date when you just get it - fresher is definately better. If the bag isn't sealed perfectly, or it has a small hole, or it is improperly stored can all impact the stuff...portland cement just loves to absorb moisture, and if it does, it may not make the bag a solid, but it may end up being a lot of cured 'sandy' particles, that won't adhere to anything.

    The guys over at www.johnbridge.com use a lot of Ditra, you might ask there.
  3. chefwong

    chefwong New Member

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    No offense to the moderator over there.....but they have a guideline on questions being posted on a *continuous* project thread and sometimes questions don't really get responded just due to the original thread questions / title ----- whereas I may even break the rule and post a good title respective to the question being asked, only to have the thread moved into the *project thread* or what I call the blackhole...

    Concrete is the base. The goal is to screed flat (not level but flat) and then Kerabond/Ditra/Kerabond/Tile.
    Methinks it will be 2 phases - mainly due to tile still being on the boat....and phase 1 will just be flat, kerabond, ditra and fill in the waffles.
  4. chefwong

    chefwong New Member

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    Location:
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    Some more questions if any tile pros may come upon this thread


    Mapiceme
    Anyone use this. I have used their Planipatch eons ago and hated it.
    What I like about Mapiceme is that it's rapid set....and can go down to 4".
    Even laticrete most competing product is 1/2".
    And the latter I was looking at, Sakrete B1, their set time was not as fast as Mapiceme but decent at 2" fill level as well.


    -http://www.mapei.com/US-EN/product-d...89&IDLinea=103
  5. chefwong

    chefwong New Member

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    Last but not least

    THE GREAT DEBATE
    Modified vs. Unmodified WITH DITRA

    For example, I used Lat 254 and may have even used it as thick as 1 1/4" inch - porcelin tile over concrete. I have had drills drop ontop as high as 6 feet....at least 4 times since I have it installed and no damage to the tile whatsover

    I'd be inclined to set the Ditra and fill in in the waffles with modified...
    Bearing I'm not laying tile ontop for another 2 weeks, I would think that the modified bed might be stronger than non.
    Warranty or not....
  6. BobL43

    BobL43 DIY Senior Member

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    My personal experience with the John Bridge web site has been great. all my questions I keep in my project name thread, and If I have new question to ask relating to my project, I just enter a title in the title box up at the top of my reply. Has worked great so far. Everything I asked has been answered for me by the pros.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,143
    Location:
    New England
    You need to understand the chemistry of modified verses unmodified...a modified mortar has components that must dry to achieve the system's full strength. It must outgas water vapor for this to occur. Essentially, a modified is a layer of a laytex type material that encompasses a matrix of cement. The laytex provides a protective barrier around the cement and is stickier. Until the laytex dries, it is easy to tear the bond. Think rubber band verses a concrete block.

    Ditra is essentially waterproof. Porcelain tile is essentially waterproof. The drying can only occur via the grout line gap, and if you decide to fill it with grout before that happens, it can literally take months to achieve its strength (concrete based products strength is based on curing for 28-days - an unmodified achieves more sooner when placed between two waterproof surfaces like Ditra and porcelain). While, eventually, this will happen, if you walk on or move heavy object over the floor, you may crack a tile or break the bond. Because the manufacturer has no control over that, and few installations would restrict access for that long, they tell you to use a (good) unmodified. They will give you an approval to use a rapid set modified, but that is not something a typical DIY'er should ever consider. A rapid set modified will achieve enough strength to prevent most disasters, but will still take forever to achieve the stated full strength. IOW, a good unmodified may provide equal strength, but not quite as fast. The rapid set would allow a pro to potentially set and grout in the same day.

    An unmodified thinset only needs to cure...if there were excess moisture (within reason), it would not affect the curing time or the strength (too much moisture, and you will compromise the strength, though). This is predictable. So, while a modified may have a higher ultimate shear strength, that difference would be lost if you didn't allow things to cure AND dry properly, and it means an extended 'keep off' time.

    A good unmodified thinset (not the entry level, cheap price leader which is mostly sand!) will typically have a shear strength of 300+ pounds/sqin. A good modified may increase that by a third. But, take a typical 12" sq tile 12*12*300=43,200 pounds! Are you really expecting to need more than that? The Ditra would debond long, long before the tile would break off the mortar.

    Compressive strength is in the same ballpark, and if you had a point load big enough to be an issue, you'd crack the tile first anyway with either.

    If you want to fill the waffles first and can let it sit for a couple of days, you could use modified for that. But, I'd still use unmodified to set the tiles on it. I've dumped a clump of modified out on newspaper and let it sit for a few days prior to throwing it in the trash...in the center, it was still soft and springy. That doesn't happen with an unmodified as it will cure anaerobically.

    Any manufacturer (with any kind of integrity) spends a lot of time prior to making recommendations on how to use their product...do you really feel you have enough info to second guess them?
  8. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Mapecem Fast Setting Screed Mortar is my favourite product for shower construction. At 15-16 per bag that is a ton of technology in one 40 pound bag. Love love the stuff. 1/4" - 4" in small areas. 1/4"-2" in larger areas. You need the Admix for a slurry coat as well.
    Last edited: Dec 7, 2011
  9. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    It is crazy to install Ditra and use modified thinset on top??? It's not allowed by Schluter and why void your warranty. Go pick up Spider Web from Custom or Dural online. Both embrace modified thin set and you do not void your warranty. That way as well you can use your premium thinsets.

    You will love the mesh over top of these products. It is a positive mortar lock or so they say. I find it helps slice up the thinset when filling the waffles and the product is easier on the knees than ditra. With ditra it's hard to get your mortar filled in perfectly.


    [​IMG]

    You are forcing a solid mass into a dish so air is trapped, much like drywalling and filling the screw heads. For some reason the mesh with the Spider Web makes this process a little easier.

    [​IMG]
  10. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Jim if you just dropped Schluter from your recommendation list you could have some much more free time. People do not want to understand the chemistry. People do want warranties.

    To install Ditra over plywood you need two thinsets. On to install the ditra to the plywood and one to install the tile over top.

    Most dry set mortars (which are rarely used) in off the wall locations are expired or over a year old.

    At least when you push the amazing powers of dry set mortar remind people to check the date codes.

    Since most people use modified thinsets most modified thins sets are fresh (ie under six months old).

    So it is easier to buy a product and tile that accepts modified thin set.

    If the installer wants "Crack Surpression" Ditra doesn't even do that. Noble Seal TS does and can be ordered online and shipped right to the door.

    Jim you have been brain washed by the giant Marketing Machine that is Schluter Systems.
  11. jimbo

    jimbo Plumber

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    I don't think the installer needs to UNDERSTAND the chemistry. jad apparently does, and his explanation tells us WHY we should FOLLOW the recommendations of the manufacturer when we decide to use their product. WE don't need to know the chemistry, just READ the instructions!

    As to purchase of supplies, you can make your best estimate, but if you don't include a factor for waste...will you use every last ounce of mortar from every bucket you mix up???......then you will end up making a trip back for more. How much is that inconvenience worth, compared to the price of an unused bag?
    I'm sure a professional tile contractor gets pretty good at their estimating, but I guess they usually have an extra bag of mortar on the truck just in case!
  12. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Exactly

    Mapecem Screed mortar gives 14.5 square feet coverage at 1/4" thick. Per 40 pound bag. These measurements are very accurate.
  13. chefwong

    chefwong New Member

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    710
    Location:
    District of Columbia
    Project is quite underways....

    ended up using Mapecem
    Ultraplan M20
    Kerabond
    and Lati 253 Rapdiset....

    All good stuff......
  14. BobL43

    BobL43 DIY Senior Member

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    Location:
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    Hi John,

    I went onto Custom's website and saw all their info on the Spider web matting and mortar, but I see that the mat is sold only as 30 Sq meter (323 Sq ft) rolls. Is there anyplace to buy smaller quantities, as I only need about 50 Sq ft of the mat. I have not called Custom to find out yet, just thought I'd ask here first. I like the concept of being able to use just one type (modified) thinset.

    Thanks,

    Bob
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    22,143
    Location:
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    Pretty much everyone that sells an unmodified, also sells the admix separately...one bag, dual usage, you can get modified when needed, or unmodified when not.

    With any cement based product, shelf-life is an important issue...the quality of the store and turn-around all play a big component in what you get. Just a little moisture can turn a bag of mortar into cured sand particles over time...it may or may not have been enough to make it a solid blob, but it won't hold a tile properly. Never use an old bag, or one that has 'chunk's in it. You're risking things if you use an opened bag that has been sitting around for a bit unless you were REALLY careful about sealing it back up again, and never longer than the shelf-life date code.

    Just like you shouldn't buy an outdated bottle of milk, that doesn't mean you may not find one on the shelf...it is just one of those things you, as a consumer should check.
  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Location:
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    As I read their spec sheet, this should be 3/8" minimum over a slab, and when over a subfloor, at least 1-3/8" thick. On a subfloor, it requires a cleavage layer and lath. If you were going to put a surface waterproofing layer on it, it would be an expensive way to do things when a sand mix would work for a lot less. If it was a preslope, should work. Since it is not porous, you shouldn't use it as a setting layer in a shower (again, unless using a surface waterproofing layer). You have to mix it with an aggragate and water or their admix, so now you need a bunch of materials. Since your sand or gravel would likely have some moisture, you need to be skilled enough to not add too much extra water. Fine for someone that uses it a lot, maybe not so good for a DIY'er.
  17. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,143
    Location:
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    SpiderWeb is an interesting product. The thing that actually holds the tile in place is the bond between the thinset and the bonded on fibers. The pockets then act as pillars to hold the tile up. Ditra works in a different manner...the pockets still hold the tile up, but they are shaped like a dovetail, preventing the mortar from pulling out of the pockets. The mortar on the topside doesn't actually adhere to the membrane much, so it has some flexibility - the floor and the membrane can move independently of the tile and the mortar since they aren't bonded together. On SpiderWeb, you are relying on some of the fibers from shearing off the substrate to maintain a monolithic tile layer, and others to actually hold the mortar in the pockets and to the membrane. Different concepts, similar results. Use of larger than 12x12" tile requires different subfloor prep. This isn't true with Ditra. SpiderWeb should use their recommended SpiderWeb thinset. Ditra, any quality dryset. Both likely quality products...Ditra has been in use much longer with a good track record.

    If you're interested, this short video shows how the Ditra uncouples the tile from the substrate: http://www.schluter.com/7214.htm
    Last edited: Dec 7, 2011
  18. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    One of your local suppliers will sell it by the foot. Don't call the box stores - call the tile stores. Most tile stores in Vancouver will sell shorts.

    If you can't find a supplier you can use Noble Seal TS instead of either Ditra or Spider Web. Noble Seal TS can be ordered right to your door step and as I mentioned earlier preforms better than Ditra and Spider Web.

    "Uncoupling" is a Schluterized Invention Word. Their is I believe no ANSI test for "Range of Uncoupling". Again Marketing.

    Ditra the plastic that makes it "Waterproof" is thinner than Kerdi. Kerdi is 8 mil or roughly 1/4 the thickness of your credit card. Noble Seal TS is 30 mil.

    You do the math.
  19. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    Jim you kill me.

    Do you get to go on the Schluter Company Get Aways?

    I bet you have never installed Dural Durabase or Custom's Spider Web, let along a full roll of Ditra.

    Just so I get this straight your saying Ditra is better than Spider Web? Where do you draw this fact from.

    I think the Ditra warranty is 3 years. Is that right? Maybe 5.

    If you use any modified thinset you get a 7 year warranty with Spider Web. If you use Customs own mortar you get a ten year warranty.

    Which company do you think has more faith in their product Jim? My money is on the one with the longest warranty.

    Again, shame on you for selecting only half the story to share in your efforts to promote Schluter's products.

    Just so no one thinks I'm being mean to Jim here, here is a link to the Spider Web PDF http://www.custombuildingproducts.c.../spiderwebuncouplingmat.aspx?user=dis&lang=en

    I ordered my last roll of Dural Durabase from ProSource.

    The cost of it was juts over a dollar a square foot. Here in Vancouver in the box outlet's Ditra sells for about $3.00 a square foot. Closer to $2.20 in the tile stores. So even with shipping the Dural is cheaper than Ditra.

    Now Spider Web is a Custom Building Products product. It might be slightly different from Dural's Durabase.

    Maybe call Pro Source as see???
    Last edited: Dec 8, 2011
  20. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    OMG - that is funny. Your apparent counter sales points are endless. If you where in fact in this business and actually mixed thinset and applied waterproofing products daily you would be "Skilled Enough" to know that all mortars have a water level requirement. That should be followed.

    For Mapecem Screed Mortar we use a hair under two litres per 40 pound bag. Every mortar requires different amounts of water, every thin-set, every grout. This is why we read the bags.

    It might surprise you Jim (since you promote Schluter as a way to pass your retirment and not build showers like me) that the suppliers have this figured out.

    So if your worried about not being skilled enough to mix a bag - practice measure a cup of milk. Try a few times if you mess up. Sometimes you might need to add a little more if you stop pouring to quick.

    Now imagine your mixing bucket actually was on giant measuring cup!

    [​IMG]

    Tada Magic.



    Imagine that in every paint store they sell liquid guides.

    Every box store has one.

    No worry your skilled enough.

    Jim you promote Kerdi hard and as well the dry pack. Mixing dry pack is an art. Many pro's make a special bucket. I use a my Makita and a garden hoe. How do you mix your dry pack? I mean how did you mix it for your mom?

    JW
    Last edited: Dec 8, 2011
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