Roman/Jcuzzi tub surround construction

[jgwufgator]

I did a quick search and don't see exactly what I need, so let me pose this question.

I had to (and am currently working on) replace my shower stall and we are also replacing our old roman tub/surround with a drop-in jacuzzi tub. The frame that was there was too tall for the new tub, so it has been torn out. I am getting ready to construct a new frame, but I need to know how thick the deck of the surround is going to be before constructing the frame (so the tub flanges sit over (but not directly on) the deck. I figure it will be the 2x4 fram, wooden deck (OSB or plywood), moisture barrier, backer-board, thinset, tile. I do not want the deck supporting the tub at all. I just want it flush with the top of the deck.

To do this, I was planning on constructing the deck exactly as before, except actually putting some sort of moisture barrier between the durock (or hardibacker) and the wooden deck. What material should I use? The shower will be kerdi, but I'd like to know if some poly sheeting or tar paper would be sufficient between the durock and the deck. Also, if tar paper or plastic sheeting is used, is it nailed to the wooden deck or is it thinsetted? Can the durock be thinsetted to the tar paper or poly sheet? It seems like putting nails through the protection completely compromises that protection.

Thanks for any help.

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[Mike2]

Hi Josh, you need to alter your materials sequence somewhat.

The waterproofing layer on your tub deck (horizontal surface) goes on top, not sandwiched in between. So alternatives would include something like plywood/OSB, thin set, backer board, and a liquid/troweled-on waterproofing membrane like Custom's RedGard, then tile. Or you could skip the backer board entirely and go ply, Ditra, then tile. Ditra can be completely waterproofed by placing Kerdi Band over the seams.

[jgwufgator]

Maybe the waterproofing used by the original installer was the greenish stuff I saw under the thinset.

Thanks for your help.

Edit:
I will add that I am thinking Ditra/Kerdi is too expensive, as the tub will not be used EVERY day.

[Mike2]

Two coats of RedGard (approx. $35 a gal. at Home Depot) should do the trick. Yep, I bet that green stuff was just another brand. RedGard is just one of many.

You can see it here on Custom's website. http://www.custombuildingproducts.com/ProductCatalog/SurfacePrep/WaterproofingAntiFractureMembranes/RedGard.aspx?user=pro&lang=en

[jgwufgator]

Thanks again.

One last dumb question. What kind of coverage can I expect from a gallon?

[Mike2]

One gallon coverage of RedGard is 35 to 40 sq. ft., two-coats with a combined dry film thickness of 47 mills. You'll see all that on the back of the container. Or go here for more product information. http://www.custombuildingproducts.com/docs/data_sheets/RedGard%20DS%2011-06.pdf?user=pro&lang=en

:)

[dontnomuch]

In response to post #2, can you install the CBU over the plywood with screws or do you use thinset to avoid holes in the CBU?