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Unread 03-08-2018, 07:20 AM   #17
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Join Date: Jul 2005
Location: Fairfax, Va
Posts: 4,271
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Help me noodle out this floor build up

Rough in plumbing is nearly finished, the in-floor work passed inspection yesterday, so I'm about ready to close up the floor and need to get my head around the next steps.

I'm doing a curbless shower using the Durock shower system, using one of their custom sized pans. The pan will be 1" thick at it's perimeter. I am also installing a heated floor (probably Ditra Heat), but not running it into the shower. Shower floor tile and main floor tile will be the same thickness.

I have 3/4" T&G ply set between the joists on full length cleats, done to both increase strength for the large format tile and to get the floor both level and flat.

My current thinking is to lay another layer of 3/4" ply over the entire floor, staggering the seams from the first layer, then the pan on top of that. Durock says to set the pan using a 1/4" X 3/8" square or U notch trowel. Then mortar and their membrane on top of the pan using a 3/16" x 3/16" v-notched trowel or 1/8" x 1/8" square or u-notched trowel. The membrane is 1/64" (12 mil). I will probably run the membrane onto the main floor by a couple of inches. to cover the main to shower floor transition.

I don't know what the mortar layers will squish down to. My brain already hurts.

Now onto the main floor. which needs to match the height of the membrane'd shower pan. Can anyone suggest what combination of CBU or ply, mortar, and Ditra heat mat will get me there? I can certainly use thinner ply under the shower pan. I don't have the mortar or Ditra heat thickness spec's.

Any and all feedback is most appreciated!
If I recall correctly my memory is excellent, but my ability to access it is intermittent.
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