Posting this so that it might help another house restorer...
The 1890's era rental house that we purchased here in Cincy had a room on the second floor in which the plaster had fallen off of a chimney and the brick underneath had corroded. It was generally a disgusting mess. There also was a huge old stovepipe hole in the middle with a rusted out piece of ductwork.
Suggestions to repair it ranged from screwing on concrete backerboard or some kind of screening and then using joint compound.
I decided to replaster instead...after taking out the stovepipe and surrounding bricks and replacing them. I used plaster mixed with water and a little white vinegar to retard the fast drying time. Regular plastic corner beads were attached on both sides so that the chimney would again be square...just pushed gently into the plaster. Plaster has the advantage of being able to be applied heavily...but dries quickly.
After covering the brick with approximately 1/2 inch of the stuff, I used joint compound as a finish coat. It was time consuming but worth it.
Attaching stuff by drilling into the mortar would have been a real headache...I feel that my solution is more authentic as well.
It looks great and is hard. I'll send photos if anyone is interested. Thanks.
Oh, that chimney only functions as a vent for a water heater.
Dean in Cincy snipped-for-privacy@aol.com