Masonry Chimney to a Class A Chimney
Many times a masonry chimney will be deteriorated and need to be torn down. But it may not need to be torn down all the way to the ground. Maybe it runs in the middle of the home and is nearly impossible to remove the masonry down to the basement.
You can tear the chimney down to where it is solid again, many times just to the attic floor, and then rebuild the chimney with double wall Class A Chimney pipe. This may be the safest way to rebuild the chimney if the previous masonry chimney had a severe bend or corbel in it.
This chimney may be too dangerous to rebuild with masonry again because of the severe corbel. A much safer alternative is to use a factory built chimney with an anchor plate. This anchor plate will bolt to the bricks where they are in solid condition and sealed with high temperature silicone. The one side of the anchor plate is flat to make a bonding surface with the brick. The other end has a male end that accepts the Class A chimney pipe.
Below the Class A Chimney pipe, you should install a stainless steel liner in the existing masonry. To transition from the stainless steel chimney liner to a Factory built chimney, use a transition plate.