I need to remove and replace an old stove vent pipe made from 8" or 9" terra cotta pipe inside a galvanized sleeve. The pipe runs 11' floor to ceiling in the kitchen and extends an additional 16' into the attic. I've been told roofers will sometimes lift the sections of terra cotta out from the roof, but haven't found anyone in San Francisco willing to do this work. I'm currently thinking of building a frame around the duct to support it and then cutting the steel sleeve and removing the terra cotta pipes. Any suggestions?