Flash existing CMU and stucco chimney? Best practice?
The roof of a new addition will wrap an existing chimney, and the roofplane/chimney intersect will come at a place where the chimney structure is parge-and-stucco over CMU blocks. So what do we do? Knock off all that finish to get to the CMU face, where we want to flash? Sawkerf into the mortared joints? Lay in the counterflashing with horizontal leg and a hook-lip, and then re-mortar, then re-stucco? Does this all go in two layers of metal, the first stepped into roofing or flashed to where we aren’t stepping? The second, the counterflashing, is the one that is going into the chimney? Or do we just demo all finish plus CMU above where we want to join, and then lay it in as one would do in new construction? I am not going to be doing this, but am doing the plans and specs for the work. I want my instructions and details to represent best practice. Whatever that is.