Expert: James Ball - 10/3/2011

Question
This is a follow up to a question about the use of Hydraulic cement on a chimney/ cap.  I have seen a lot of mortar and caps worn out due to water damage.  One common problem I see is the crown separates from the flue and water is getting in.  If I clean out the cracks, is the use of Hydraulic cement okay?  Is there a better product to patch and seal it?

Answer
Hello Tim, Hydraulic cement is used in a wet environment and not for a crown, so if you get the right mortar and replace the whole crown (leave 1/2" gap around the flue tiles and fill latter with silicone) that should do the trick, just filling the cracks will only by you time, and may last a month or several years.
James