Terry's Tips are personal observations based on my experience and seeing the cause and effects of things. There may be many ways to address different problems and all opinions are welcome. I am always open to suggestions and certainly want you to correct me on any mistakes that might be written.
If you look and listen to your house, it will talk to you. Are you listening?
This is why I recommend to have a rain cap installed. We can see the cap over the flue is not helping protect the rest of the chimney. Water is the enemy here. A properly sized rain cap that is slightly larger than the top of the whole chimney will protect the top, not just the flue. This is now going to be a much more expensive repair. I would also recommend a brick sealer (like Chimney Saver), that stops moisture absorption but does allow any moisture in the brick to dry out. If you see moss growing it is a sign of to much moisture, and this goes for roofs as well.