Fireplaces, Heating Stoves, Flues and Chimneys - concrete chimney cap

I,ve got some water leakage coming in thru the chimney bricks behind the wall. I was going to redo the concrete cap and was told it might have a seal under the concrete between the bricks and clay flue liner. I've never heard of this and was wondering if it was common. Any other suggestions as to what might cause the leaking would be appreciated. Thank you

I need to do the same thing for mine, but not because of leaks, but to ease cleaning of the double flues. I plan on removing the concrete lid and support bricks completely, repointing the areas around the flues, sealing them well, and have a metal cap and flue extensions fabricated to "roof" over the area, allowing individual caps on the flues that can be removed for cleaning, and prevent water infiltration. Not sure if it would work for you, however. Just an idea.

There are good illustrations at http://www.maconline.org/tech/design/fireplace1/chimneyd/chimneyd.html that show how to achieve a watertight chimney.

Also, look here:

Chimney Caps To Last A Lifetime (http://www.1stchoicechimney.com/documents/Tops-to-Last-a-Lifetime.pdf)