Bolstering Flashing Seals

Flashing on your roof...wait a minute, flashing on your roof?! What will the neighbors think? Okay, let’s begin again.

Sometimes, problems arise when the seals around flashing are worn away or fail over time. Renewing seals is a little messy, but not terribly complicated and can save you some big bucks, if you have the time and energy to do it yourself. Below are the most common flashing seals you may have to deal with.

How To Seal Chimney Flashing
Use a hammer and chisel to chip out the mortar and caulking joining the flashing to the chimney. It is easiest to use a cartridge of roofing cement inserted into a caulking gun. Caulk the lines between the chimney and the cap flashing, as well as the lines between the cap flashing and the step flashing.

How To Seal Valley Flashing
Carefully lift the shingle edges along the valley flashing and slather roofing cement on the flashing. Extend the cement 5-6 inches beyond the shingle edges to ensure coverage.

How To Seal Vent Flashing
Use a caulking gun to place a generous bead of roofing cement between the vent pipe and the vent flashing (the cone-shaped support for the pipe). Now gently lift the shingles surrounding the vent flashing and slather roofing cement beneath their edges up to the vent flashing. Make sure all borders where the shingles meet the flashing flange (the flat section beneath the vent flashing) are sealed with cement.

How To Seal A Skylight
Carefully lift the shingles around the skylight and layer roofing cement under them and across all joints up to the flange (the metal girdle of the skylight box).

How To Seal A Drip Edge
At the edge of your roof there is flashing along the rake (sloped edge) and drip (straight) edge. To seal the flashing along the rake, carefully lift the shingles along the downward slope and slather roofing cement beneath them all the way to the rake’s edge. It is important not to seal the drip edge along the flat face of the eave, as this will block the holes placed along the drip edges that drain water.

How To Seal Flashing Along A Dormer
To seal flashing along a dormer: Use a chisel to chip out any old caulking. Caulk the joints between the flashing and shingles or siding with outdoor weatherproof caulking or with roof cement. Also caulk any seams in the flashing itself.

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If you need any more information on how to sealing flashing, take a look at our Roofing forums and ask questions and share tips with other do-it-yourselfers.