How to Repair a Chimney Leak

Updated February 21, 2017

Chimney leaks can become a serious problem if you don't take care of them. Water can damage brick or mortar work and moisture can find its way inside your home. Brick work needs periodic maintenance, including sealing to prevent chimney leaks. You can find leak repair materials at your local home improvement centre and make repairs in just an hour or two. Common chimney leaks may include flashing leaks or loose brick and mortar.

Turn on the water spigot in preparation for using your garden hose. Climb up on your roof, using an extension ladder. Harness yourself to the chimney in case you fall. Pull a coiled water hose up onto the roof with the help of an assistant feeding the hose up the ladder. Have your assistant climb up onto the roof and harness himself to the chimney also.

Inspect the roof flashing for leaks by hosing down the outside of the chimney, where it meets the flashing. Use the spray nozzle to control the water flow. Have your assistant inspect the inside of the chimney for any leaks by using a flashlight to look for any leaks inside the chimney. You may also notice a gap or space where the flashing tar has been worn away. This may be the cause of the leak.

Scrape away any worn out or torn flashing seal, using the metal scraper.

Insert the flashing seal into the silicone gun applicator. Cut the end of the flashing sealant at a 45 degree angle, using a utility knife.

Squeeze the silicone gun trigger until it is tight against the tube of flashing seal. Apply the flashing sealant to the area around the flashing, where it meets the chimney base. Apply a bead of flashing seal, just like you would apply silicone to a tub. Let dry for several hours without getting the flashing wet.

Repeat the process by running one more bead all the way around the flashing. Let dry overnight if possible, without getting the flashing wet.

Remove all loose mortar using a large screwdriver.

Apply brick mortar using a silicone gun and mortar tube.

Smooth out the new mortar, using a smooth finishing trowel.


Some flashing sealants are designed for wet weather applications, so if they get wet, they will still seal properly.

Things You'll Need

  • Extension ladder (high enough for roof access)
  • 2 body harnesses
  • Garden hose with sprayer
  • Flashlight
  • Metal scraper
  • Flashing sealant
  • Utility knife
  • Silicone gun applicator
  • Large screwdriver
  • Mortar
  • Smooth finishing towel
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About the Author

Joey Pellham has three years experience teaching writing courses in China. He specializes in home improvement/do it yourself and parenting articles. He has written for publications such as Associated Content, Triond, Wordpress, and Blog Spot. Pellham has been freelance writing since 2008. Pellham studied at Washington State University.