Oozing chimney
I have a 100 year old home with a working fireplace whose chimney is exposed on the 3rd floor of the home. The portion of the chimney on the 3rd floor was covered with some sort of light cement coating. The cement coating has several cracks in it, and is seeping a thick, dark brown liquid. It's not pouring out; the liquid will ooze out of a crack and then very slowly run down the chimney over the coating. I had the chimney reflashed, which seemed to help, but there is some new oozing going on. A chimney sweep did an inspection and said that it looked fine to him. What could be causing the seeping? It does get hot up there in the summer, and this has happened in both summer and winter. Also, I'd like to repair the coating. Do I need to remove the old coating or can I put a new one on over the existing one?
You need to tear off the coating to get to the root of the problem. That way you can determine what is causing the oozing-deteriorated bricks, a buildup of creosote, or some 1930's waterproofing stuff or whatever. Here is a chimney we redid about 1995 that had an oozing thin red liquid from deteriorated terra cotta blocks:
Note the metal pan on top. That was my idea. It seems water ran down the flue year after year and deteriorated the mortar between the terra cotta blocks and the flue popping off the stucco. The roofers made the metal pan but unfortunately out of galvanized metal, which later rusted and now the chimney has rust stains on it. A better solution would probably be stainless steel or at least paint the pan to keep it from rusting. This pan should have been bigger for better protection against water infiltration. A better solution is to redo the cap. My rubber membrane method works real well. Please click to see it...