fj12ryder wrote:
That looks very much like the damage I had to repair this last summer. My problem was caused by the poor sealing done around the vent flashing on the outside. There was no sealant around the top part of the flashing and water would come in, run down the wall and soak the wood. You couldn't tell a thing was wrong until the floor was gone. No stain, no swelling. The wall below the vent also had to be replaced. That was a real pain.
Thank you for your insights. And for anyone keeping score: I took out an electrical plug in that wall - directly above the damage - to get a look inside that wall. No signs of water in the wall and the insulation was completely dry. Diagnosis continues....