What is a chimney crown?
A chimney crown is a masonry roof that covers the top of your
chimney. It prevents water from seeping into the masonry below.
A cracked or deteriorated chimney crown can lead to serious and
costly problems with the chimney
and the house.
Here is a typical chimney crown from a house made in the 1970s
or 1980s:

Water will sit in the cracks and the cycle of freezing and thawing
will cause them to get deeper and wider. Eventually water will
be able to enter the interior of the chimney between the flue and
the outer walls. This water will then damage the inside of the
chimney and cause costly damage to the surrounding walls and ceilings
in the house. Often times, when the chimney crown is broken it
makes and excellent place for birds, squirrels and raccoons to
make a home.
What is the solution to chimney crown problems:
Some chimney crowns are in such bad shape that they must be torn
off and completely rebuilt. However, if not allowed to deteriorate
too far, most crowns can be repaired. We start by patching the
cracks and deterioration with proper repair mortar or cement. We
then cover the crown with a flexible waterproofing sealant that
will protect it from water damage for many years to come.
We use an excellent waterproofing product called CrownCoat that
carries a 10 year warranty. (For more info see: www.chimneysaver.com)
This product can also be applied in cold weather making it ideal
for use any time of year.
Finally, we install a proper chimney cap on the flue to prevent
water and animals from causing damage to the fireplace.
Here is the above chimney crown properly repaired:

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