How To Check & Re-seal Your Roof Flashing

The rains have a way of letting home owners know that is it time to get up on the roof and inspect the roof flashing.  Water can enter through the roof’s flashing if the seal has been broken.  Before major water damage occurs, you should check and re-seal your roof flashing as soon as possible.  Better yet, before the rains come, it would be a good practice to check your roof flashing for areas where leaks may occur and re-sealing should be done.

Materials needed

You will need a couple of items to re-seal any leaks found in your roof flashing.  These items are:

  • Hammer
  • Chisel
  • Roofing cement
  • Caulk
  • Caulking gun
  • Ladder for going up the roof (if necessary)

Checking and re-sealing instructions

Here is what you need to do:

  • Inspect the seal between shingles.  If upon observation the seal between two shingles has been compromised, re-seal it using roofing cement.  The roofing cement should be applied under the shingles by the drip-edge (which are strips of roof flashing), never by the eaves.  Make sure to spread the roofing cement evenly and coat the flashing well.  Be very careful in lifting the shingles as these are prone to damage if not handled properly.
  • Check the valleys.  Another area to inspect is the valley flashing.  You should raise the shingles near this area.  Place roofing cement approximately six inches away from the edge under the shingles.   Spread the roofing cement well.
  • Examine the vent flashing.   This supports the pipe you see jutting out of your roof.  Instead of just using roofing cement, you need to use caulk as well.  With enough caulk in the caulking gun, apply a good amount of caulk in between the flashing and the vent pipe.   Place a splotch of roofing cement under the surrounding shingles and spread this well.  Some roofs have a flashing flange beside the vent flashing.  If this is the case with your roof, place roofing cement in between the flashing flange and the vent flashing.
  • Inspect the chimney area.  In order to seal the area between the chimney and the flashing, mortar and caulk is used.  First remove the caulk using your trusty hammer and chisel.  Remove all the caulk and clean the area of the chimney and cap flashing.  Apply roofing cement around the cap flashing and the step flashing.
  • Check the skylight.  If your roof has a skylight, you need to check the seal.  The skylight box should have a metal girdle or flange.  Raise the shingles in this area then apply roofing cement under the shingles as well as on the joints right up to the metal girdle.

Reminder:  If you are not sure what you need to do, it is best to call a professional roofer to do the job for you.

In areas where surfaces intersect, water can enter if these are not properly sealed.  Roofs have different kinds of flashing that serve as extra protection against water seepage.  You can find flashing around chimneys, skylights, vent pipes, vent fans, roof valleys, roof deck intersections and other areas as well.  The flashing can be made from aluminum or galvanized steel.

Generally, if properly installed, water should not seep in and cause water damage in your home.  However, nothing lasts forever so you need to properly inspect and re-seal your roof flashing.  This is the only way to protect your home and avoid unexpected home repairs.


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