Bumps in Ditra Installation


Old 04-24-18, 10:33 AM
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Bumps in Ditra Installation

We are having an issue with our Ditra installation and are wondering our options. This is our first time tiling and installing Ditra after doing other home renovation projects. We installed the Ditra over a flat OSB subfloor. We used a level to determine the floor was flat before staring the install (not perfectly level but it was flat). We used Schluter All-Set and the Ditra trowel to install the Ditra then the next day used a 1/8 trowel to install Kerdiband on the seems and near the tub. We now are testing the tile to make sure everything is cut correctly before tiling and notice three of the tile are uneven and rocking. This is happening at tiles that touch the Kerdiband. The bumps seems to be no more than 2 inches wide and between 1/8 to 5/32 inches tall. Is this something with proper care to ensure the tile heights are the same we can take care of during install? If so how do you do this? Do we need to replace the Kerdiband or Dirtra? If so how do we make sure we don't have any leftover mortar messing up the next install? Thanks for your help. Here is a link to a video of the tile rocking to see how bad it is. https://photos.app.goo.gl/kctRjJCaRhoRy27j1
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Old 04-24-18, 12:17 PM
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You really have nothing to worry about. The thinset that the tiles are bedded in will be able to compensate for the rocking you see when laid dry.
Old 04-24-18, 01:01 PM
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What size tiles are you setting,

Do not use that 1/8 trowel, that is too small for even the smallest of tiles!
Old 04-24-18, 01:08 PM
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Join Date: Apr 2018
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Thanks for the reply. We used 1/8 trowel for the kerdi band We planned on using a 3/8 in. x 1/4 in trowel for the our 12 x 12 inch tiles that are 3/8 inch thick .
Old 04-24-18, 01:38 PM
Join Date: Jan 2006
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You will be fine with that trowel. Next time, install the Kerdi-Band at the same time you install the tile.
Old 04-24-18, 06:05 PM
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Yes, your notched trowel will compensate and allow for cushion to jump the bump in the membrane. Just be aware that a 3/8" x 1/4" trowel will require you to watch carefully the tiles as you install them so that each adjacent tile is at the same level as the next. Personally, I prefer 1/4" x 1/4" trowel as there is less squish of the thinset.
Old 04-25-18, 06:37 PM
Join Date: May 2007
Location: USA
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You said the humps are 1/8 - 5/32" high. Yikes, that's too much deviation.

Adding Kerdi Ban shouldn't add more than its thickness, which is .008 of an inch. I would remove the Kerdi Ban and try again if you really think you need it in the first place.

BTW, unless you're planning to completely waterproof the floor, Kerdi Ban on Ditra seams is not needed.


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