What actually does an uncoupling membrane do?

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Jadnashua

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An uncoupling membrane provides a break between two rigid surfaces. IOW, it allows both surfaces to move independently. When you bond tile directly to a rigid surface, say concrete or cbu, or even plywood, the thing between them must have enough flexibility to keep the stresses low enough so that the bond can keep them attached. When that bond between two rigid surfaces is thinset, that thinset must have some flexibility, and that is why you may need a modified thinset to reliably hold things together when bonding directly.

But, if you've ever touched something like Ditra, you'd know that it is a flexible polyethylene matrix. While the membrane's fleece IS bonded to the substrate, thinset does NOT stick to Ditra, and there are voids between the pillars that hold the tile up which means that if a lateral stress is applied, the whole tile and thinset layer can move totally independently of the subfloor or slab only restricted by the flexibility of the Ditra membrane. The membrane can move MUCH further than any difference in the expansion coefficient of the tile and any rigid substrate. Therefore, while the bond to a tile is less strong than that when you might use a modified, that bond is made under ideal conditions (the water is trapped, and can allow the cement curing to complete growing the crystals that actually create the bond to their maximum capability) and the thinset and tile can move without putting any stress on the tile-thinset bond. Plus, when you use an unmodified thinset to bond things, the cure occurs in a reliable timeframe. I was in a class this week, and the instructor talked about one test they did using a glass tile over a waterproof membrane (Ditra). You could see the thinset through the tile, and could tell the difference between 'wet' uncured thinset and cured. They watched that tile for 90-days seeing that grey spot shrink, until it finally was entirely dry. This is the reason Schluter doesn't want you to use a modified thinset over Ditra...until that modified thinset has fully cured, it is still soft and being conservative, they do not want your installation to fail...a dryset (unmodified) thinset has many times more strength than the stresses that can be applied through the flexible Ditra uncoupling membrane. Think of the Ditra as the modifier in your thinset, and it can stretch MUCH more than a modified between two rigid surfaces AND, it reaches that strength in a know, short timeframe. IOW, if you understand how this works, your trepidation about modified goes away when told to use an unmodified when using Ditra.

Note that porcelain tile and glass has been used in tiling for many centuries - many churches and public buildings are still up and in use after hundreds of years with their tile intact. Porcelain tile was first used in China somewhere around the 1300's. Modified thinsets weren't invented and only came into use in the middle of the 20th century. And, the cement they used to hold the tile in place was much less pure than what is in today's thinsets. A dryset mortar is mostly cement and sand or other inert fillers. Those old installations used an uncoupling layer to isolate the tile from any movement. Ditra does the same thing, and is most reliable using today's modern equivalent cement product - a dryset mortar.

Whenever not using an uncoupling layer, a modified thinset IS a good insurance, but is a detriment when used over a waterproof uncoupling membrane like Ditra.

Because of the fleece on both sides of Kerdi, you get a similar, but by no means as extensive, uncoupling. But, also consider that a typical shower is composed of much smaller sections than a large floor system, and that is enough. That's also one reason why the TCNA calls for the changes of plane in a shower to not be grouted...this means that each wall and the floor are independent and not impacted by the other sides, and those sides are relatively small, keeping the shear stresses down. If the shear stresses are kept in check, the bond strength of the mortar is at least 150psi with any mortar, and a good dryset can achieve upwards of 300psi under ideal conditions. A modified can achieve more (not all do), but if the shear stresses are relieved, there's no way you could ever pull a tile off that surface unless you use excessive force - way beyond any normal day-to-day use factors.

If you're interested in more, watch the video on Ditra here http://www.schluter.com/videos.aspx
 
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Eurob

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JW said:
My testing is "Blue Collar" style. I have no lab. No machines. I just pit two uncoupling membranes against one another.

As long as the tests are done in the same manner and approach from A to Z , the data can be relevant . At least for the one doing it and can help others if comparable charts are attached to it .



Jim said:
when you use an unmodified thinset to bond things, the cure occurs in a reliable timeframe. I was in a class this week, and the instructor talked about one test they did using a glass tile over a waterproof membrane (Ditra). You could see the thinset through the tile, and could tell the difference between 'wet' uncured thinset and cured. They watched that tile for 90-days seeing that grey spot shrink, until it finally was entirely dry. This is the reason Schluter doesn't want you to use a modified thinset over Ditra...until that modified thinset has fully cured, it is still soft and being conservative, they do not want your installation to fail...


But maybe those modified thin sets -- not that Ardex and other ones need air to cure -- where used at 10°C and 90%H and the unmodified ones where at 22°C and 40%H when Schluter made the observation(s) . If you want to incorporate all of the modified ones in the same '' panier '' , it kinda looks like a garage test conclusion .

If anyone is interested in more infos about the uncoupling , I will copy and paste more of the same or similar to the post #1. IOW , providing links to the same .
 

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Jim....stop being a shill for Schluter. Being book smart is way different than actually doing.
You took a class 2x, big deal. Get CTEF certification and guys in the industry will take you a bit more serious. Anybody can puke out info from websites. There are tricks of the trade that you will never get from manufacture websites or data sheets.
Surprised Schluter even charged you to take the class. Most times everyone attending doesn't pay a dime.
 

Jadnashua

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FWIW, if you feel your application requires a modified, you can get a blessing to use a rapid setting modified over Ditra. Ditra has been on the market for much longer than the other uncoupling products listed above. A rapid setting modified will gain enough known, predictable strength for practical use over a waterproof membrane with an essentially waterproof tile (porcelain by definition has less than 0.5% absorption by weight of water).

From the TCNA handbook:
Uncoupling membrane: An uncoupling membrane is a plastic membrane system geometrically configured to provide air space between the tile and the substrate to allow independent movement between the two and limit the transfer of stresses.

Only a couple of the many products listed by John Whipple are uncoupling membranes, and those have all been introduced many, many years after Schluter started selling Ditra. Most of those listed are crack isolation or sound suppression membranes.

From the TCNA Handbook:
Crack Isolation Membrane: Crack isolation membranes (ANSI 118.12) for thin-bed ceramic, glass, and stone installations act to isolate the tile from minor in-plane substrate cracking.

Uncoupling and crack isolation membranes have two very different purposes, and comparing them, or grouping them in the same category shows lack of understanding of their purpose and application. An uncoupling membrane protects the installation from differential expansion/contraction between the substrate and the tile relieving almost all shear stresses. It is for this reason that there is NO need to bond the tile with a modified thinset. The fact that porcelain and glass tile installations have survived intact for centuries with an uncoupling layer (in the old buildings, it was a compacted sand layer) and the tile held down with just an ancient, unpure version of modern cement says something, if you'll listen...uncoupling membranes work, and unmodified thinsets work on top of them.

When thinset was introduced, people tried to bond their tile to rigid surfaces directly using unmodified thinsets (all that were initially available). It often failed. To solve that, modified thinsets were developed. The thinset manufacturers have a vested interest to have your installation work, and a modified thinset, being more flexible (but NO WHERE NEAR AS FLEXIBLE AS A QUALITY DECOUPLING MEMBRANE!), they can be used successfully. But, compare the price of a premium modified to an uncoupling membrane with a premium unmodified that performs better, and the advantages start to show up in both performance and costs. The thinset manufacturers are quite interested in selling the higher profit modified thinsets than the much easier and cheaper to make unmodified.

They each have their place. Knowing what that is, and applying it properly is important, and as shown above, not always understood.
 

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Jadnashua

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Some of the benefits of Strata Mat over their leading competitor is the larger roll size. This makes for less installation waste and a more efficient use of product. The product is also much easier to see the coverage underneath since the Strata_Mat is translucent.

FWIW, the largest roll size of StrataMat covers 323sqft...the largest roll of Ditra covers 323sqft. The Strata mat is wider (45" verses 1M or 39.4") so a roll of Ditra is longer, but waste because it is bigger roll, more BS. It could be said that if using it on a big room, the longer roll is a benefit. And, note, that Ditra can become waterproof by banding the seams...StrataMat cannot be made waterproof. If it matters to you, the cutoff pieces of both can be used to fill in any area, and while if you were trying to waterproof it with Ditra, you'd be using more banding, as an uncoupling membrane, either of the two can be pieced together with no waste at all using cutoffs, if desired, with no loss in performance.

IF you understand how an uncoupling membrane works, you'd realize that ultimate shear strength of any of the products WAY exceeds any practical need. Shear stress becomes a big factor when direct bonding tile to a rigid substrate, but is no practical differentiator when using an uncoupling membrane. The goal is to keep the tile in place. An uncoupling membrane can do that quite well without using a modified thinset. BTW, a premium thinset mortar at say Lowes, costs over $30. You can get a premium dryset (unmodified) elsewhere for about $12-15, depending on the supplier. The materials costs are similar...guess which one the mortar industry makes more profit on? Guess which product combination provides better uncoupling? An uncoupling membrane, simply using a dryset mortar to hold the tile in place.
 

Jadnashua

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Most times everyone attending doesn't pay a dime.

I never mentioned a charge to attend a Schluter workshop...all you have to do is get approval to attend, and show up. The class is intended for tiling professionals, architects, builders, store owners and sales people, and others by exception and approval. The idea is to ensure people understand the products, and provide hands-on to reinforce what was learned, so that the products can be used properly without issues.

The information provided on uncoupling membranes is pretty generic, but I did mention Ditra, but it functionally applies to any of them. The basic fact is that Schluter is more conservative than most, and as a result, provide a method that will always work, rather than most of the time.

FWIW, in Europe for the Eurozone, you have to get multiple countries to agree on something, and Schluter tried, but failed to get concurrence on how to use and install some of their products...the politics were just unmanageable, so they relented. The US, was hard, but at least some understand, and this is why they have a different installation method between the two areas. The science is there, the testing data to back it up is there, whether you choose to ignore it is up to you.
 
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Eurob

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Modified mortars ..... used for setting porcelain over uncoupling membranes --->>> PROVAFLEX , SPIDERWEB , STRATAMAT <<<---...... all manufacturers recommend it .

There is no misunderstanding in between US manufacturers which in the same time are making the mortars and agree on the same . On top of it all porcelain manufacturers agree on using a modified mortar for the installations .

Data? ...... In the specs . :)
 

Jadnashua

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And, all those porcelain and glass tile that have been installed over the last 5-6 centuries with just cement over an uncoupling layer are now going to fall apart because the manufacturers tell you you must use their more expensive thinset product on a new install? Unmodified thinset sticks to porcelain just fine...and, when installed over an uncoupling membrane, you have far less stress to cause it to fail than you ever could produce in a practical install. Install porcelain or glass without an uncoupling membrane, and yes, you have a high risk of failure using the same materials. As a result, there is a generic recommendation to use modified with that type of tile. Just look at the spec sheets of the mortars...the unmodified ones all list the bond strength with various tile. The industry standard minimum is 150psi, and most produce a significantly higher bond. A premium dryset, cured under the ideal conditions like between two impervious layers can significantlyexceed their generic spec and some can achieve 300psi range. That can be higher than a lower end modified. Which one is the better choice? The one that performs reliably in a known timeframe that still exceeds any rational need, or one that has been shown to take three months to achieve that? There is just no significant shear stress on a tile when used over an uncoupling membrane - their whole purpose is to relieve that stress. So, then, the important thing is to keep the tile attached to the substrate. You aren't going to pull a tile off of one of today's engineered uncoupling layers unless you are trying to destroy the install. So, with the shear accounted for, and the pull off taken care of, there is no need for a modified in this situation.

Again, take the uncoupling membrane out of the equation, the situation is radically different. Then, the adhesive is providing both shear and pulloff strength to hold the tile in place. But, that is not the subject of this discussion.

Schluter does not manufacturer any thinsets in the USA. Many (not all) membrane manufacturers' prime product line is mortars. Which one do you think they're going to recommend? An inexpensive dryset, or a premium modified at 2-4x the cost? Centuries of field experience with unmodified (essentially cement with sand in it) with an uncoupling layer should say something. It works.

A tiled floor over an uncoupling membrane is like placing it on ball bearings...it can move easily without stresses. Compare that to one glued down where the substrate and the tile are expanding and contracting (i.e., moving against each other) at different rates - the glue better be really strong and elastic or things can get ugly fast, but because of the ball bearing effect, the layer over the uncoupling membrane just lazes along, stress free. There's no need to hold onto the tile with any stronger material...over an uncoupling membrane, it is locked mechanically into the membrane, not attached to it like when installed over cbu, a slab, or plywood - there's nothing (as in expansion/contraction) trying to break the tile free.
 
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Eurob

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And, all those porcelain and glass tile that have been installed over the last 5-6 centuries with just cement over an uncoupling layer are now going to fall apart because the manufacturers tell you you must use their more expensive thinset product on a new install? Unmodified thinset sticks to porcelain just fine...and, when installed over an uncoupling membrane, you have far less stress to cause it to fail than you ever could produce in a practical install. Install porcelain or glass without an uncoupling membrane, and yes, you have a high risk of failure using the same materials. As a result, there is a generic recommendation to use modified with that type of tile. Just look at the spec sheets of the mortars...the unmodified ones all list the bond strength with various tile. The industry standard minimum is 150psi, and most produce a significantly higher bond. A premium dryset, cured under the ideal conditions like between two impervious layers can significantlyexceed their generic spec and some can achieve 300psi range. That can be higher than a lower end modified. Which one is the better choice? The one that performs reliably in a known timeframe that still exceeds any rational need, or one that has been shown to take three months to achieve that? There is just no significant shear stress on a tile when used over an uncoupling membrane - their whole purpose is to relieve that stress. So, then, the important thing is to keep the tile attached to the substrate. You aren't going to pull a tile off of one of today's engineered uncoupling layers unless you are trying to destroy the install. So, with the shear accounted for, and the pull off taken care of, there is no need for a modified in this situation.

Again, take the uncoupling membrane out of the equation, the situation is radically different. Then, the adhesive is providing both shear and pulloff strength to hold the tile in place. But, that is not the subject of this discussion.

Schluter does not manufacturer any thinsets in the USA. Many (not all) membrane manufacturers' prime product line is mortars. Which one do you think they're going to recommend? An inexpensive dryset, or a premium modified at 2-4x the cost? Centuries of field experience with unmodified (essentially cement with sand in it) with an uncoupling layer should say something. It works.

A tiled floor over an uncoupling membrane is like placing it on ball bearings...it can move easily without stresses. Compare that to one glued down where the substrate and the tile are expanding and contracting (i.e., moving against each other) at different rates - the glue better be really strong and elastic or things can get ugly fast, but because of the ball bearing effect, the layer over the uncoupling membrane just lazes along, stress free. There's no need to hold onto the tile with any stronger material...over an uncoupling membrane, it is locked mechanically into the membrane, not attached to it like when installed over cbu, a slab, or plywood - there's nothing (as in expansion/contraction) trying to break the tile free.


This is exactly why -- stopped look and listen -- you don't understand how the unmod works in real conditions -- all the time -- , especially when you prefill .

The pricing for mods -- over all -- is actually lower than the unmods -- $$ which reflect the use over Schluter products -- . The price of a premium unmod is equivalent with a medium modified -- no air required to cure and '' lower end '' as you call it -- , but just to repeat what Schluter is saying is wrong -- check the facts --.


What is this called ? -- http://www.indianafloorsllc.com/ProVa-FlexTileUnderlayment.aspx


:mad::mad::mad: Oh , I almost forgot , we have to DISREGARD the mortar manufacturers recommendations , but Schluter's .... Shame , shame , shame :mad::mad::mad:
 
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Jadnashua

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An uncoupling membrane is NOT a crack isolation membrane, and the size John Whipple talks about is totally irrelevant when installing it. That he lists mostly crack isolation membranes and sound isolation ones in his list of uncoupling membranes gives you an idea that he doesn't understand the differences. That uncoupling membranes can also provide some crack isolation is still irrelevant since the tile is NOT bonded to the substrate - it is mechanically held in place on top of the membrane. The size argument doesn't hold up when using an uncoupling membrane, but it does apply to a dedicated crack isolation one. A little knowledge doesn't always lead to the proper conclusion - one needs all of the facts.

Strata-mat has some good points, but it is totally unsuitable if you are trying to also use it as a waterproofing membrane. And, consider this: thinset for the tiles does NOT stick to Strata-Mat or to Ditra, a tile is MECHANICALLY connected to the mat on the surface, so there is NO requirement for it to bond to the mat at all. If the thinset on top of the membrane did bond with that underneath, it would lose some of its uncoupling. It is locked into the geometric shape, so all the thinset has to do is bond to the tile, with a horizontally flexible mat structure underneath it there is almost no shear stress on the tile at all...why all of the fuss about a modified. If 200-300psi bond strength isn't enough to your tile, you have bigger problems than using any thinset on that job. Both a modified and unmodified has plenty of compressive strength which is handled by the pillars of thinset in the pockets of the geometric structure of the mat.

Schluter is shipping about one million square feet of Ditra a week...one would think that if there were problems, one would hear about it. Understand the products, ignore stereotypes and preconceived notions, have an open mind, and you'll see under these circumstances, it works. Be focused on killing the messenger at all costs, and you will miss some useful information. Use the products as they were designed, and you will not have problems, assuming you have any reasonable workmanship.
 

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From one of many , a very respected manufacturer of mortars and all types of membranes , including the uncoupling one -- Stratamat -- .
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Latex in mortars -- http://www.laticrete.com/portals/0/tds/tds107.pdf
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Stratamat and Modified mortars -- http://www.laticrete.com/portals/0/tds/tds147.pdf
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Needless to mention the shipping and production capabilities , including ALL of the necessary needs for the tile and stone industry under one and united warranty .

LATICRETE ...one of the few out there .
 

Vegas_sparky

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What conditions would prompt you guys to use an uncoupling membrane? Seriously, after hearing Ditra/Strata Mat/Greenskin for over a month, I don't know what this stuffs actually for.
 

Vegas_sparky

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Okay, I read that, and it ended with more modified/unmodified.

I'm wondering under what site conditions do you use this stuff. Tile over wood, tile over concrete, inside, outside. I'm sure its not a solution without a problem, so what's the problem?
 

Jadnashua

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Okay, I read that, and it ended with more modified/unmodified.

I'm wondering under what site conditions do you use this stuff. Tile over wood, tile over concrete, inside, outside. I'm sure its not a solution without a problem, so what's the problem?
If you don't know the answer by now, you may never know.

A good reason to use an uncoupling membrane is when you have something like an acceptable subfloor, have say hardwood in one room, and want to add tile to another and keep the heights the same. Obviously, you could have a ramp for a transition if they weren't, but let's take that to a bigger extreme and say you have 24"OC supports. Tiling directly to the plywood requires a second layer of ply, then, while you could tile directly to the ply with a heavily modified thinset, you'd almost certainly not have the two rooms end up even. While I know pros that do regularly tile over 2 layers of ply directly, it gives you little room for error. Using something like DitraXL, in one step, you can match up with hardwood with a typical tile, and get a reliable install...that's one good reason for using an uncoupling membrane.

Another is if you want to waterproof the surface, something that StrataMat can't do on its own, under the same circumstances above.

ANother is if you really don't want to carry maybe a thousand pounds of cbu up to the third floor, and then drive hundreds or maybe thousands of screws into the floor to hold it down over the thinset.

Or, if you want to avoid the dust from cutting cbu, or, if you'd need to make a bunch of narrow cuts on cbu...an uncoupling membrane is much easier to do with no dust, and you can easily carry enough for a good sized room in one trip.

Or, well, maybe you get the idea.

Most of the products on John Whipple's list, as I already said, are NOT uncoupling membranes....if you understand English with reasonable reading comprehension, that means that SOME of them are....I never said NONE of them were, just that most of them weren't, they are either crack isolation membranes or sound suppression.

While you can use a crack isolation membrane just over cracks, there are really two kinds of cement slabs: those that have cracked, or those that will eventually crack (in that case, where would you put it, over the whole floor?). While there may be somewhat rare exceptions, and since an uncoupling membrane can also generally perform some crack isolation functions (but it does NOT work the other way!), it can make some sense to use one over a slab.

Then, consider the GC wants you to tile the newly poured slab yesterday, but it was just poured. Without something like an uncoupling membrane that deals with vapor management (there's more than one out there), you'd have to wait 28-days if you wanted to follow the thinset manufacturer's requirements...you can tile the floor as soon as it is safe to walk on with those uncoupling membranes. A green slab shrinks a significant amount during that 28-day curing period AND releases a lot of moisture. Keep in mind that cement actually gets stronger if you can keep moisture in it...that is one reason why they sometimes get wetted, or covered with a tarp or plastic when strength is an issue - an uncoupling membrane does a better job.

So, if you do not know when to use one, maybe you need to get a little training yourself. They are good insurance, and when you include the cost of the cbu, the tape, the fasteners, and your body lugging all of that stuff around, not counting the effect of loading your work vehicle when you can have the customer pick up your order and safely throw it in the back of their car (or you, which probably happens the majority of the time), or your back is not as good as it used to be, you'd be well served to learn about and consider using uncoupling membranes.

It's not all about 'need', they are easier to install, and can provide the ability to install and warranty an install with lots less prep than not using one. When you can get another job into your schedule in that week because you didn't spend the time playing with 3x5' sheets of cbu and piles of screws where you could layout, install, and tile the job with an uncoupling membrane, your profit goes up, you can show the customer the benefits, and earn more.

So, be stubborn, ignore they exist, don't use them where you can, and be forced into transitions that aren't always necessary or not getting those jobs in new or remodels with new slabs because you don't understand what an uncoupling membrane can do and your competitor does. If you won't consider them, your competition will. I'm just trying to help explain why they work and how to actually use them to your advantage.

And, because the average DIY'er probably doesn't even know they exist, telling them about them in this format has some merit.
 

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I'm not trying to start another shit storm. The last sentence of your post summed it up perfectly, Jim. I have actually wondered for the past month under what kind of circumstances these products would be useful. Thanks for clarifying it a little more.
 
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