Traditional Shower System vs Schluter's Kerdi Shower System - Which dries faster?

Discussion in 'Shower & bathtub Forum & Blog' started by johnfrwhipple, Jul 17, 2013.

  1. johnfrwhipple

    johnfrwhipple I love these ACO Shower Drains - Best in Class

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  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    IN a conventional shower, when you get the grout saturated, it wicks into the mudbed which is quite porous if done right. If it is used often enough, that moisture can accumulate until there's enough to cause it to run to the weep holes.

    In a surface membrane shower like Kerdi, moisture can still penetrate the grout joint, but thinset is thinner and denser than a mudbed, so it doesn't tend to penetrate as far or as fast. Plus, if the thinset is embedded into the fleece on the Kerdi, and its depth is within normal standards, it doesn't tend to go that far.

    Keep in mind that unless you've got a porous tile that can absorb a fair amount of water, the only path to the membrane is through the grout joints. If it can't be drawn further into something like the mudbed, the only place for it to go is back up and out. The moisture wants to dissipate, that's primarily up with a membrane, but can go both directions when there's a mudbed - then throw in gravity, and it may tend to go down more than up. Conceptually, I don't see it spreading under the tile much in a membrane situation, but could easily see that happening in the porous mudbed.

    When you throw in the fact that we're talking miniscule amounts of water per shower being absorbed, without the sponge of a mudbed beneath to direct it down and potentially accumulate, it doesn't tend to happen with a membrane (given good workmanship - good thinset coverage, full grout joints, proper slope).
  3. johnfrwhipple

    johnfrwhipple I love these ACO Shower Drains - Best in Class

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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Just keep in mind, a typical shower has standing water in it (and only often on a small part) for the duration of the shower and easily less than a minute after you stop...there is NO standing water. A tight grout joint won't absorb much except when totally immersed, and then it can take awhile. So, in a typical shower, my guess is that water may never get much more than to the bottom of the tile, and then, over a membrane, only want to go back up. On a mudbed, I think it would tend to wick down should it reach the bottom of the grout joint...lots more surface area to spread out once there rather than up through that small joint.
  5. Yersmay

    Yersmay Writing, constructionDIY Member

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    At the risk of being the village idiot, I will jump in with some questions. In an earlier, different thread John posited the idea of using something called Ditra-Mat in an old fashioned mud bed. In review, I believe John was concerned that the topical membrane with the layer of thinset above it tends to hang on to water longer than one might expect. If I remember correctly, John wondered if in the long run the porous mud bed would wick water down and away from tile or stone and the drainage plane in the Ditra-Mat would carry the water to the drain weep holes effectively. If I recall, Jim replied that this would be dubious in that the mud bed would eventually become saturated and basically hang on to the water... and on balance it would not be as good as a topical membrane. (I hope I have that right, Jim).

    But I've been thinking a lot about Ditra-Mat because of its internal drainage plane. Somehow it just seems like this is a good idea if it could be harnessed. Is there any way that Ditra-Mat could be utilized as a topical membrane? In theory, if water passed through grout it would fall into the Ditra-Mat drainage plane and be easily routed to the drain. The fact that John did not pose this as a possibility probably means it is impossible. But could someone explain why this couldn't work somehow. Thanks in advance.
  6. johnfrwhipple

    johnfrwhipple I love these ACO Shower Drains - Best in Class

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