Flashing protects the vulnerable seams in your home from water.
Installing it correctly helps to ensure your home will be leak-free.
Roofing and siding will protect most of the walls of your home from water
penetration, but certain junctions of your home need additional material to
keep water out. Flashing covers the vulnerable seams on your house. These
seams are generally found where there is a joint between dissimilar
materials, movement between two aspects of the building, or both. Two
common areas where flashing is needed are the chimney and around doors and
windows. These tips will help you to install flashing correctly in those
Chimney and masonry flashing.
Creating a weatherproof flashing joint against masonry can be challenging,
but is essential to seal off areas around your chimney.
When installing flashing on bricks, chisel out a slot in the mortar joists
that is about a half-inch deep, then fold in the top edge of the flashing
and fill the joints with fresh mortar.
If you are dealing with stucco, as opposed to bricks, cut out a shallow
groove with a circular saw fitted with a masonry-cutting blade. Then place
the top edge of the flashing into the groove, and cement it in place.
A less effective method is to secure the flashing against masonry with tar,
adhesive or caulk. This will probably work for a few seasons, until the top
edge of the flashing will pull away leaving water free to run behind it into
Door and window flashing.
The sides of doors and windows can be sealed with caulking, but you will
need flashing across the top since this area is most exposed to the weather.
Many doors and windows come with a molded strip of vinyl flashing, but you
can use metal as a replacement.
When working with new construction or a remodeling project, you will have
room to tack flashing to the wall and cover the upper edge with siding.
When replacing old flashing, remove a course of siding, or pry out the
bottom edge and slip at least an inch of the flashing underneath. If you
remove a few shakes or clapboards, be sure to tack the flashing with roofing
nails along the top edge of the flashing, where the heads will be concealed
once the siding is refastened. The exposed section of flashing should
extend across the top of the window or door trim, and then tuck around its
Most vinyl flashing will curve away from the building to cover the trim. Be
sure you don't crimp the curved section when you fasten the siding. You can
always trim the lower edge of the siding, which will allow it to be nailed
tightly against the wall without putting any stress on the flashing.
Source: Mike McClintock, The Washington Post.