how can I still be confused with waterproof debate

DaWolfmanMarch 25, 2012

I started my tub surround project intent to put in new shower surround with the existing cast iron tub. I 4 mil polyed all 3 sides to the stud. I then faced delima on whether to put greenboard to just above tub lip or behind tub and to the floor.I had concerns to where water would go.Buddy helping so buddy win argument and behind it went. Now a gift of free tile was given to me so i switched things and am now going tile . I know putting up another vapor barrier can cause a vapor lock but should I be concerned about water getting behind tiles,backerboard and greenboard then beading down the poly and resting on my subfloor.the green board is siliconed to the tub and I'm ready for durock to be installed . Should anything be between those 2 boards. Should I tar paper over green board first if so should it be #15 pound Building Paper instead of tar paper.Should I RedGard over durock instead so water can come back in to tub area? My Brain itches. So many things to consider.

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whatever ya do buddy just don't make two wonderful membranes that are parallel to each other all over because this makes a moisture sandwich which always builds up and rots... anything else is not as importnat as this, ya got it now?

    Bookmark   March 26, 2012 at 3:24PM
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What was the purpose of the green board?

The water barrier behind tile ends at the top of the tub.

I is a not a vapor barrier, but an actual membrane to stop water.

Water goes through the grout in a tile wall, and then through the cement board just fine.

    Bookmark   March 26, 2012 at 4:36PM
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How does water go horizontal through grout and than through thinset, and than through cementboard? I have a open framed room behind our shower, and never see water running down the clear plastic sheet. Is that a myth? Is that form of construction no good anymore? And how does the water get out of the bottom being it is caulked? Wouldn't this water remain captured behind the plastic?

    Bookmark   March 26, 2012 at 9:16PM
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water = humidity = moisture = presence of H2O =
not necessarily "running" as a liquid down the clear plastic sheet.

Water can evaporate behind caulking. Water can seep anywhere and pile up anywhere if it is encase between two membranes.

    Bookmark   March 27, 2012 at 12:16AM
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