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Hisgirl 01-01-2009 07:46 PM

Moisture mystery in midst of shower redo
Hi all...I could really use a good opinion.

1. We had a leak from an elbow of our bathtub jets. The wood floor under the tub box was wet and the moisture had spread around. We removed all the tile and tub to replace it with a non jetted tub.

2. Found another leak under the shower pan from hole in grout. Mold had built up. Remove all mold and cleaned and dried area out.

3. Removed all tile from shower stall and took it down to insulation and studs. Found mysterious beaded moisture behind insulation. Came to conclusion it was from moisture trapped with nowhere to go. Aired it out and watched it during a hard rain. No more moisture.

4. Put up hardie backer board in shower stall in prep for tiling. Now, days later, prior to tile, am seeing water stains in seams of cement backer board. :mad: Have NO idea where it is coming from.

Took some boards off and there isn't any wet behind it or on the insulation ....rains coming in so we'll watch it. If it's roof issue, which we can't see any reason it would be, I would suspect it would dribble down in a rain...or would have that first day when we found it and it poured. But we saw nothing. Roof is about 8 yrs old.

Could the hardie board have sucked moisture from the air while the wet wood floor spots were drying out?

What if we watch it during the rains and there's no moisture running down the corner 2 X 4s and no moisture showing up at all..... I'm scared to go ahead and tile with those mysterious stains showing on the seams.

Any advice?

Just Bill 01-02-2009 06:41 AM

You are supposed to coat the seams with thinset/mesh tape, could be moisture from the thinset..?? Hardibacker does not soak up or pass moisture, but moisture can get thru (Duroc)cement board.

Ron6519 01-04-2009 09:01 AM

Did you put up a vapor barrier on top of the studs and behind the backerboard? I mean a 6 mil continuous plastic barrier, not kraft or foil faced insulation. Cold air from the exterior could be causing condensation as it hits the warm interior air. That interface would be the backer board.

Maintenance 6 01-05-2009 09:29 AM

Having the wall opened up likely caused the issue. You have allowed warm moist air to penetrate to the outside cold wall surface. If you have checked to be sure it is not from rain water or a roof leak, then I would re-insulate it and install a good vapor retarder. 6 mil poly would be good, especially in a bathroom. Once that is properly installed, no more moisture will be able to penetrate the wall system.

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