Sealing a chimney flashing

The chimney flashing prevents water from seeping into the house from the roof. Any leaks must be fixed right away to avoid any further damage.

Tools and materials needed

  • Extension ladder
  • Masonry Trowel
  • Hammer
  • Silicone caulk w/caulking gun
  • Flashing cement


Get a ladder and get on the roof.

Use a ladder that can either be hooked to the roof or can stand up by itself. If you have a normal ladder, have someone hold it while you use it. Using a safety harness that is attached to a secure part of the roof is recommended. Also, attach a rope to the toolbox to help you rise is rather than climb a few times to get the tools on the roof.

Remove the old seal

Peel and scrape off old sealant to prepare the area for the new sealant. When you are done, apply the sealant.

Flashing refit

Reposition the flashing back into before applying cement or caulk. Use a hammer to gently hammer the metal sheets back into place. Be careful not to hit too hard.

Apply caulk

Apply the silicone caulk and be sure to reach every small gap. The edges of the flashing must also be covered with caulk. Apply as much as you can.

Applying cement

After the silicone caulk has dried, apply the cement, using a masonry trowel. Spread it even on the flashing. You could apply it just on the edges too. Anyway, the cement will do it’s job.

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