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Unread 02-09-2011, 08:13 PM   #1
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Join Date: Aug 2010
Location: Northern Virginia
Posts: 8
Stu's master bathroom remodel


First post on the forum. Have enjoyed occasional visiting and reading for several years now.

I am in the middle of a master bathroom remodel. Have completed the demo, plumbing changes, and most electrical. Starting to detail plan the floor. I am looking for guidance about floor height and types of thin-set. I am not a pro, but enjoy doing home projects (some tile experience… two full-bathroom ceramic tile replacements jobs, floor and bath/shower, but never used radiant heat or isolation and final floor height was not an issue)

My plan is to install tile and radiant heat on the bathroom, vanity room, and closet floors as follows:

9. tile (porcelain, 3/8" thick, 18" square, over three rooms, about 117 sq. ft.)
8. thin-set (3/16"? for larger format tiles)
7. isolation membrane (ditra 1/8")
6. thin-set (1/16"?)
5. radiant heat mat (1/8") (nu-heat custom one-piece mat over three rooms, about 68 sq. ft.)
4. thin-set (1/16"?)
3. new underlayment (3/8in ply)
2. existing subfloor (19/32in T&G ply)
1. existing joist (2x10, 12ft unsupported length, 16"o.c.)

I'm concerned about the tiled floor height and the transition from the bathroom to the carpeted master bedroom. The thin-set thickness above are my estimates based on my readings here.
3/8 underlayment + 1/16 mortar + 1/8 mat + 1/16 mortar + 1/8 ditra + 3/16 mortar + 3/8 tile = 1-5/16" total height -- assuming I got the thickness estimates close… yikes! that's pretty high. Am I headed down a path that will lead to a large height difference from tile to carpet or is this manageable?

One thought I had was to ditch the plywood underpayment altogether and do a subfloor / heat mat / ditra-xl / tile approach. Schluter claims the ditra-xl is good over 19/32 T&G with 16"o.c. joists. That would save about 1/4 inch in height. Is this a better approach… a good compromise to floor strength, tile isolation, and floor height?

And here's what I think I know about the mortar:
- layer 4 under the heat mat = acrylic or latex modified thin-set (as spec'd by nu-heat)
- layer 6 under the ditra = latex portland cement (as spec'd by Schluter)
- layer 8 under the tiles = unmodified thin-set (as spec'd by Schluter)
Is there a particular brand that is recommended for any of these, or is what I can get at HD okay (figured I could use Versabond for the modified thin-set layer 4)? I'm happy to get specific types at the local tile place if that's the better route.

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