Intent 1:
To limit the probability that:
- heat from a flue pipe will be conducted into unprotected
chimney masonry, which could lead to damage to the masonry in the
vicinity of the flue pipe connection,
- rainwater will flow across the chimney cap and into
the flue, which could lead to damage to the liner due to freeze-thaw
stresses, which could lead to the ingress of condensed water vapour
into the cavity between the chimney liner and the surrounding masonry,
which could lead to damage to the masonry due to freeze-thaw stresses,
or
- mechanical or freeze-thaw damage to the extended portion
of the liner will lead to blockage of the flue or subsequent freeze-thaw
damage to the upper courses of surrounding masonry.
This is to limit the probability of
the collapse of the chimney, which could lead to harm to persons.