Chimney flue chase cap rain cap spark arrestor not installed : Masonry chimneys are almost always capped
with mortar to prevent rain water from entering the system. Excessive
water will cause accelerated deterioration of the fire box and the
chimney itself. This cap, called the "flue cap," seals the
chimney liner to the outer flue or bricks. The flue cap is sloped
outward for water runoff. Cracks are commonplace on the flue cap and
those that measure less than 1/ " will usually not be mentioned by
the inspector. Excessively large cracks should be sealed with new
mortar, mixed with a fortifier for a better bond to the old material.
The installation of a rain cap is always a good idea. Keeping water out
of the chimney will extend the life of the entire system. Rain caps or
spark arrestors are available at most home improvement stores.
Manufactured or "zero-clearance" fire places usually have
framed flue chases.