Chimney mortar bricks or blocks loose cracked. It is common to find the top rows of bricks loose
enough to fall off. This condition should be repaired as soon as
possible. Damaged chimneys are common in earthquake prone areas. Damage
to brick and block chimneys is common in areas with very cold winters.
Moisture entering the brick or block freezes thus forcing the outer
layers of the masonry material to slough off (exfoliation). Possibly the
application of a waterproofing material would help. Loose and damaged
mortar joints will lead to the destruction of the chimney. If the
condition is advanced repointing the joints may be in order . Contact a
masonry contractor for assistance and additional information if
necessary.