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Unread 05-20-2022, 09:09 PM   #1
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Join Date: May 2022
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Filling between gypsum greenboard & permabase cement board?

Hi all, hoping to get some advice. Partially through repairing a failed shower pan/curb, previous contractor had glued tile directly on wood around the shower opening/curb and glued tile to greenboard on the shower walls. I've replaced the bottom 20 inches of the shower wall and encased the opening/curb with permabase plus. What can I use to fill in the inch or so gap between the gypsum greenboard and the permabase as in the pictures?

My plan to is to apply liquid waterproofing (redgard/aquadefense) and fabric waterproofing (corners/seams/etc.) over the permabase, existing greenboard and whatever I use to patch the gap between the greenboard and permabase.

Since this is in the shower, drywall compound is not going to work. I'm thinking either thinset or expanding foam under mesh tape (Great Stuff Gaps & Cracks). I'm leaning toward Aquadefense over Redgard because it's got gypsum listed on it's TDS, and Great Stuff instead of thinset to fill the gaps.
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Last edited by tileywiley; 05-20-2022 at 09:15 PM.
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