How to Caulk Flashing


A leak in the roof of your home doesn't always mean trouble with the roofing itself, gaps or tears in flashing is often the culprit. Flashing is the material that covers areas of the roof where two different materials meet. Some common areas of flashing use are where a chimney intersects with the roof, areas around vents, or the area around a skylight in a roof. Flashing is typically a durable plastic material, aluminum or copper, that can withstand the elements and keep water out of your home. In some cases, you may have to caulk around the flashing if becomes worn or damaged.

Things You'll Need

  • Ladder
  • Utility knife
  • Wire brush
  • Putty knife
  • Roof caulking
  • Caulking gun
  • Set up your ladder and climb carefully up onto the roof. Carry your putty knife, rag, caulk and caulking gun with you.

  • Remove any old caulking material. Place your putty knife between flashing and the roof or chimney and pop out the edge of the caulking. Pull out the rest of the caulking material with your hands.

  • Scrape out the inside edge of the flashing with the edge of your putty knife. Wipe the edge off with a rag to help remove any debris.

  • Allow the area to dry completely from any dew or rain before applying the caulking material. The caulking material will not adhere well to the joints if water is present.

  • Use masonry caulk to fill in flashing joints between a chimney and roof. Load a caulking tube into your caulking gun. Snip off the tip of the caulking tube. Press the trigger several times until caulk oozes from the tip. Place the tip of the caulking tube into the joint. Press the trigger and move the gun parallel to the length of the joint. Do not stop in any one spot or else you will over-fill that area with too much caulk. Keep the caulk gun moving until you fill the joint. Release the trigger as you life the caulking gun out of the joint.

  • Fill the joints with silicone caulking if you are working in areas of the roof surrounded by shingles. Lift the shingles and apply the caulk 6 inches from the edges of the shingles. Keep the caulking gun moving, as in the step above.

Tips & Warnings

  • Try to always have a friend present when working on the roof, in case something goes wrong.
  • If you are using a ladder to reach your work area, have your friend hold the ladder to steady it.
  • Call a professional roofer if the flashing you want to caulk is in a steep or dangerous area of the roof.

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  • Photo Credit Jupiterimages/ Images
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