On May 3, 9:12 am, Javier wrote:
I seem to have me a leaky shower stall...

It's lined with ceramic tiles, both the floor and the walls, there's a
single drain in the center of the stall. The bathroom is upstairs, above
the garage, which is finished with drywall, including the ceiling. A few
weeks ago I noticed some water stains on the ceiling in the garage right
below where the shower is, so I cut a large-ish square hole, and it was
indeed wet. Through the hole I see the joists, supporting OMB boards. I
guess those OMB boards are the floor of the bathroom. I see the drain
pipe coming from the shower and going wherever it goes, but the pipe
feels dry to the touch. I don't see leaks at the elbow joining the pipe
coming down from the drain to the one going sideways. The OMB board was
damp to the touch.

I took out the grille covering the drain, and looked down the pipe. I
didn't see anything other than, well, white PVC pipe.

I didn't use the shower for a few weeks to let things dry out, meanwhile
I applied some silicone caulking around where the drain fixture joins
the floor tiles (the drain fixture is plastic), and at all around where
the floor and walls join (the grout didn't look broken at all, but I
figured it couldn't hurt...)

A few days ago I resumed using the shower, and the OMB board feels damp
again.

What steps could I take next to troubleshoot this, besides calling a
plumber?

Thanks,

-jav

Have some one take a shower while you look from below