Questions & Answers

Hello. I will be installing Schluter DITRA-HEAT-DUO in a small bathroom on top of a concrete floor. The floor area is only about 25 sq. ft. Now, Schulter's coverage estimating tools only shows Schluter ALL-SET as the recommended thin-set. However, their documentation says this:

What type of thin-set mortar should I use when installing Schluter-DITRA?

The type of thin-set mortar used to install DITRA depends on the substrate material. For example, to set DITRA over plywood or OSB, a modified thin-set mortar meeting the requirements of ANSI A118.11 is used. To set DITRA over concrete or gypsum, Schluter-Systems recommends an unmodified thin-set mortar meeting the requirements of ANSI A118.1. Please consult the Schluter-DITRA Installation Handbook before beginning your tile project to confirm the proper materials selection.

The paragraph above specifies unmodified thin-set for concrete which would be Schluter SET and not ALL-SET.

I really have two questions. Schluter recommends DITRA-HEAT-DUO for concrete floors. Will this be too thick with the tile installed? I am concerned about the transition from the bathroom floor to the floating wood laminate floor. Should I use the "regular" DITRA-HEAT (non-DUO) or even the PS (peel & stick) version instead?

Secondly, if I should be using an unmodified thin-set mortar, are there any brands other than Schluter that would be ideal? I'm in Orange County, CA and only Schluter ALL-SET (modified) is locally available.

Thank you.