Schluter Kerdi shows ridges through Kerdi

nonstopJune 9, 2013

I wish I would have found this site last thursday. I have installed two walls of kerdi using hardibacker, Mapei Floor and wall tile mortar, a 1/4 x 3/16th V-notch trowel, and I can see ridges through the Kerdi all over the walls. I mixed the mortar to a milkshake consistency by adding more water, I used two trowels to embed the Kerdi in the Mortar but it just would not flatten out. I did not do the pan yet as I am afraid I need to tear it out and do it again, but I don't know what to do. I have a call in to Schluter but since its the weekend, they can't get back to me until next week. What should I do?

Here is a link that might be useful: Link to Pictures

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When did you add the "more water" ?

Did you let the bucket rest a few minutes after mixing it , and then mix it again ?

Did you wet the walls with a sponge or garden sprayer before applying the mortar ?

When you say it wouldn't flatten out, do you mean you have waves and bumps that aren't at the seams ?

    Bookmark   June 9, 2013 at 9:43PM
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I added more water from the beginning, more as in more than the mix required on the bag.
I mixed for 5 mins and let rest for 10 min.
I did not wet the walls at all.
It is flat as in, if I take a level to it, it is plumb. The ridges that the V notch trowel made did not squish into the valleys. So , I can see light and dark lines throughout the kerdi.

    Bookmark   June 9, 2013 at 10:18PM
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Your problem is you didn't wet the walls first. Hardi is VERY thirsty, and will soak up a lot of water. It actually sucks the water right out of the thinset. You need to wet it down really well, and then wet it down some more. It takes a LOT of water. A lot of people end up putting a coat of primer on it first, to alleviate the problem. I would pull down the Kerdi and start over. You might be able to scrape the thinset off of the Kerdi and re-use it. Cleaning the thinset off of the Hardi should be relatively easy.

    Bookmark   June 10, 2013 at 8:43AM
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I am pulling the sheets off and most of the mesh is still attached, but there are mortar lines on the sheets. I should be able to reuse them right?
I am trying to scrape off the mortar off the walls but it seems like i can not get it down to the hardi, is that ok?

    Bookmark   June 10, 2013 at 11:11AM
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I never use hardibacker with kerdi. I put kerdi directly on dry wall. I am not a pro but I believe kerdi can go on dry wall.
No problems so far with this method.

    Bookmark   June 10, 2013 at 1:22PM
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