OT - sweating walls

I may have mentioned here that we recently moved into a house built in the '50s. A problem has arisen.
One of the bathrooms has a relatively small shower. My wife likes to take long hot showers. When she does, a small amount of water, maybe 3 or 4 tablespoons, appears on the floor in one spot.
Doing a little investigating, there is a small "weep hole" at the bottom and that's where the water is coming from. It appears to me that the wall must be sweating on the inside as I can find no place in the shower that water could get into the wall. I'm thinking there would be more water if there was an actual leak.
Looking around on the web, all the references to sweating seem to refer to moisture condensing on the outside of walls, not inside a wall.
Has anyone here run into this problem? And fixed it? The only thing I can think of is more powerful vent fan.
Or am I worrying about nothing? Maybe the amount of water is too little to cause much harm. OTOH, maybe the other shower walls are also getting wet inside and they don't, AFAICT, have a weep hole.
Of course my wife doesn't want to believe it's not a leak - she doesn't want to use the shower in the other bathroom. No, I don't know why either :-).
Any ideas? Thanks.
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On 2/9/13 11:34 AM, Larry Blanchard wrote:

Long read, but perhaps worth the time.... http://www.buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers
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On 2/9/2013 9:45 AM, -MIKE- wrote:

http://www.buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers

improper roof install, I would look into this right away. You might have mold growing in your walls.
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Amen, brother. This requires immediate attention.
However Larry, it sounds like waaaay too much water to be condensation. I would almost bet you have a leak in your shower pan or in your grout. Get in the shower with best flashlight you have and a magnifying glass and investigate carefully every grout joint and look for cracks. A tiny, tiny sliver of a crack will result in a pretty good leak.
If nothing is apparent, then find a way to completely block the drain (I mean 100%) and fill up the shower with as much water as it will hold and leave it there for an hour. Did your water show up? Grout or tile leak that is through the pan. Repair with a line of DAP tub and tile after a thorough cleaning of the area.
Nothing? Remove the grate from the drain and inspect this very carefully to make sure it is sealed where the tile comes over the collar of the drain. To make sure of this, regardless of what your eyes tell you, when this detail is perfectly dry and perfectly clean, apply DAP tub and tile on this detail and mash it in the joint with your finger. Wait 24 hours, put the grate back on and try a shower to see if that got it.
Been doing this a long time. I have never seen condensation generate THAT much water. Doesn't mean it isn't happening, though. But these are things I call "the most likely suspects" when trouble shooting and I would start there.
Robert
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On Sat, 09 Feb 2013 11:20:00 -0800, snipped-for-privacy@aol.com wrote:

Thanks Robert, lots of things to try there. A little more detail:
Imagine the top view of the shower stall as an upside down U. The left edge of the U is flush with an outside wall. The right edge of the U has a tile wall extending 3-4 feet to the right of a toilet. About 6" of this actually extends into the U. The leak is at the bottom of that 6" section, but above the rim around the shower. So I think I can eliminate the pan and the drain but I will check them.
I looked for missing grout once before and found and fixed a couple of small places on the other walls, but nothing on the 6" section where the leak is. I'll try the magnifying glass technique and go over it very carefully. Thanks again.
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On 2/9/2013 12:34 PM, Larry Blanchard wrote:

went away. I didn't think the fan was doing a good job to begin with. Check to make sure your fan is really exhausting too, not to the attic. I saw a friend who had put his vent in the attic, he was so proud he had to show me. I told him it would create mold problem , he discounted my observation... just waiting for him to tell me his roof is full of mold... some don't listen.
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On 2/9/13 1:55 PM, woodchucker wrote:

At least it was in the attic. :-) Around here, most fans are just in the ceiling with no venting at all. Their intended purpose is simply to make people feel better when in the water closet farting away, thinking no can hear it over the fan..... which we all know doesn't work. :-)
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On 2/9/2013 7:20 PM, -MIKE- wrote:

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The water only appears during a long shower? That suggests water is getting in.
Try a hose, and spraying the wall with cold water. If you get water leaking, then the idea that a temp differential is causing sweating is shot down.
Definitely be concerned with mold, though.
I would be tempted to open the wall and see what's going on behind it. Water in a wall is Bad News, and opening a wall is only a weekend project.
djb
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Larry Blanchard wrote:

Hot water = hotter air = air with greater ability to hold water vapor
Cold(er) surface (any) + vapor loaded air = condensation.
So yes, what you suggest *could* be possible but I doubt it.
First of all, how is the vapor loaded air getting into the wall? Through the weep hole? Again, I doubt it. And what's with the "weep hole"? I have never seen or heard of such (in an interior, framed wall).
Secondly, assuming the water *is* the result of condensation within the wall, it sounds like way too much water. If the wall interior was filling up with vapor saturated air that air would be condensing on the entire wall surface. There is a wood plate at the bottom, no? It would wick up a fair amount of water as would any studs. Ditto drywall. If your thoughts are correct, there is much more water getting into the wall then there is coming out.
I don't think you are worrying about nothing, it needs fixing, but I think you need to look elsewhere for the water source. And to figure out *why* there is a hole. Have you probed it with an ice pick? Punky?
HTH & HAND
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dadiOH
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