I have an interior bedroom wall that somehow produces a brown sticky substance that runs down the wall. It looks like water has condensed on the wall but despite repeated cleaning the substance still appears brown and sticky. The wall is an interior wall constructed of wooden studs and 1/2 inch drywall. Having just cut a hole through the dry wall I can confirm that there are no leaks from the roof into the wall – all timber is dry and sound. The room has a vaulted tongue and groove pine plank ceiling which is not insulated. In other words the 1.5 inch tongue and groove only has a tar laminate roofing material on top. We have an en suite bathroom with shower that I originally thought was the cause of the water vapor, but since installing an extractor fan all other signs of condensation have disappeared. The water droplets start about 2 feet from the ceiling of the 10 foot high wall.

I live near the ocean just south of San Francisco.

Any ideas?
We do not smoke anything and generaly don’t burn food when we cook it. We’ve only been in the house just over two years and have not painted this wall yet. So if the previous occupants smoked then it could be nicotine.