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Unread 01-01-2022, 09:17 AM   #4
cx
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Join Date: Jul 2001
Location: Boerne, Texas
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Some of the MR boards (Moisture Resistant) have face coatings that are not particularly friendly to thinset mortar, Christopher, which is the reason for avoiding them in your application. I've never used the purple kind and can't really testify as to the suitability. I do know the plain white boards will work well.

Your subfloor, if in good condition, is technically suitable for a mortar shower floor. If that hole is oversized for a Kerdi drain, I'd add a second layer of nominal half-inch plywood to correct that condition.

My opinion; worth price charged.
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Last edited by cx; 01-01-2022 at 11:01 AM. Reason: Typo
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