chas045

Stop Dampness from Drain Line?

chas045
July 17, 2019

Several years ago we had our second floor fiberglass molded shower replaced with a professionally built shower. The plumber had cut in from below to do the replumbing and I had done some of the sheetrock patching and could tell where we had worked. Within a year or so, I could see a light stain that suggested a leak of some kind although the area never seemed damp, and I eventually cut an exploratory area out. I couldn't see or feel any dampness with or without water running. I guessed without any experience that perhaps condensation from hotter or colder difference between ceiling air and the drain could cause something and I shoved a little wall insulation lightly around the area and repatched the sheetrock.

I saw almost nothing more for a couple years, but my patch work began to crack away in one spot. Knowing I was going to be painting another ceiling having just added some crown molding and may as well do the other room too, I repatched the patch again with some new joint compound. However, before I could finally get around to paint, I just saw that the new compound had picked up stain. I cut back in today and found that the piece of fiberglass insulation directly under the pipe was a little cruddy, but an adjacent piece looked untouched. The sheetrock directly under the pipe was a blotchy light moldy black but clean two or three inches away. The subfloor above the pipe that supports the shower is pristine all over. The pipe, sheetrock and added insulation all seemed dry.

To me, this indicates condensation somehow. Is there something I can do to prevent a repeat? I am in North Carolina. The humidity is often above 90% and temperature likewise. In winter humidity is low and temps go between 20 to 60°F. We run AC around 77°F.

Comments (2)

  • Jim Mat

    Replace the affected area with a vent, and install another vent to allow air circulation.

  • chas045

    Jim: are you talking about the vent stack (plumbing) or are you suggesting some ceiling air ventilation device that I have never heard of. This house was built in 1999. The drain goes in two directions and I assume one is the vent, probably right there.I believe the new shower drain was built to match the original drain and just spliced in.

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