Sentence 9.26.4.4.(2)

Intent 1:

Where counter flashing is installed between a shingle roof and a chimney, to limit the probability of:

• water running down the face of masonry and entering behind primary flashing, or
• the intersection being unable to accommodate differential vertical movement of chimneys and roof surfaces, which could lead to the displacement of or damage to flashing.

This is to limit the probability of precipitation or meltwater ingress into chimneys, which could lead to damage to chimney liners from freeze-thaw stresses, which could lead to the premature failure of chimney liners, which could lead to carbon monoxide gas leaking into living space, which could lead to the acute poisoning or asphyxiation of persons.