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Old 02-25-2018, 01:02 AM   #24
jadnashua
Veteran DIYer- Schluterville Graduate

STAR Senior Contributor

 
Join Date: Jul 2004
Location: Nashua, NH
Posts: 12,357
If the slab moisture is within specs, had you considered using Ditra on the slab? It would offer a path for moisture (vapor) to stabilize, and protect from any moisture from below from being an issue. You'd want to seal the seams with Kerdiband for best effect.

That would require different mortars and likely would not work properly with the backing intact.
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Jim DeBruycker
Not a pro, multiple Schluter Workshops (Schluterville and 2013 and 2014 at Schluter Headquarters), Mapei Training 2014, Laticrete Workshop 2014, Custom Building Products Workshop 2015, and Longtime Forum Participant.
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