How To Seal Roof Flashing

caulking around roof flashing
  • 4-8 hours
  • Intermediate
  • 300-500
What You'll Need
Roofing cement
Caulk gun
Chisel or screwdriver

Roof flashing is an important component in maintaining your roof and preventing water damage. Flashing will sometimes need to be resealed because the seal can wear over time. Resealing your roof flashing is easy and you don’t need many tools or materials.

Step 1 - Safely Get on the Roof

To seal your roof flashing you first have to get on the roof. In order to do so safely, you will need an extension ladder and rubber-soled non-slip shoes. Before attempting to get to the roof, you must make sure that the ladder is secure. Climbing a ladder and walking on the roof should only be done in shoes that will provide a great deal of friction. You don’t want to injure yourself.

Step 2 - Carefully Inspect the Flashing

ladder leaning against gutter of a house

Roof flashing will be found in a number of different locations on your roof. While you are up on the roof, you should inspect all of the areas so that you don’t have to return any time soon.

Drip Edge - The drip edge is flashing that directs water into the gutters. It is found near the edge of the roof.

Valleys - A valley is comprised of two unconnected roof areas. Valley roof flashing acts as a seam protector.

Pipe Vents - These pipes allow for drainage exhaust to escape your home. Vent flashing is placed around these vents.

Chimney - Flashing is placed around the base of the chimney.

Dormer - A dormer is an area of the roofline that has been extended. You will find flashing where the dormer is built out of the original roofline.

Step 3 - Gently Lift the Shingles

Once you have determined the flashing does indeed need to be sealed, gently lift the shingles laid on top of the flashing so you can reseal them. It is important to take great care in lifting the shingles because you don’t want to cause any damage.

Step 4 - Generously Apply Roof Cement

man working on flashing near a chimney

Before applying the roof cement, you want to remove any old cement, caulk, or debris left in the area. Much of what needs to be removed will be hard. Use your hammer and chisel or screwdriver to remove the old sealant. It is best to take the time to remove the old application so that you can ensure a tight seal.

It is easier to apply the roof cement from a caulk gun than any other method. Purchase the cement in a tube that will fit your caulk gun. When applying the cement, you want to apply a very liberal quantity. Of course, you don’t want cement oozing all over your roof, but you do want to ensure a strong seal.

As you lift the shingles, apply the cement to the back of the shingle about six inches in. This will ensure that the shingle doesn’t lift off of the flashing.

For areas around the chimney, dormer and pipe vent, you may also need to pipe beads of roof cement in areas that aren’t covered by shingles. This should be very easy since you are applying the cement from a caulk gun.