Flashing a
Chimney
by Jonathan Poore
Flashing makes watertight joints at
junctions between roof and walls,
around chimneys, skylights, vent
pipes, and in valleys and hips where
two planes of a roof meet. Often, the
flashing develops leaks before the
roofing material does.
This detail shows the most complex
flashing problem: making a watertight
joint between a chimney and a shingle
roof. Chimney flashing is often
damaged, badly installed, or missing
altogether. Installing proper chimney
flashing is within the capability of the
competent non-specialist. Although
special roofer's tools make the job go
faster, the procedures described here
can be done with ordinary carpentry
tools.
Layout. Study this series of
drawings to determine what
measurements you'll need. If you have
an existing chimney flashing that was
done