How to Install Wood Stove Chimney Flashing

Chimney protruding from a red roof
  • 2-6 hours
  • Intermediate
  • 0-300
What You'll Need
Chimney flashing
Chimney saddle
Silicone sealant
Roofing nails
Brick nails
Expanding nail caps
Metal shears
Circular saw
Safety wear

Chimney flashing is essential for preventing weather from getting inside the chimney, especially excess moisture. The chimney flashing needs to be installed between the shingles and the chimney, protecting the gap from ice and water, which can quickly cause damage in bad weather. Flashing should also be installed along the saddle of the chimney.

The saddle is any sloping structure at one side of the chimney which assists water runoff. Using the suitable tools and materials, installing chimney flashing for a wood stove chimney is a fairly straightforward job. It should not present a problem for anyone who is comfortable with common DIY jobs.

Step 1 - Install the First Section of Flashing

The chimney flashing will already be bent as required. Cut a section of this for installing around the front of the chimney. Cut the flashing using metal shears. The ends of the top section should be cut at a 45 degree angle as well. Bend the corners you have cut around the chimney, and attach it in place using galvanized roofing nails. Also, attach the flashing along the front edge with more nails.

Step 2 - Install the Remaining Chimney Flashing

man working on chimney flashing

Cut and install the eight-inch square sections of chimney flashing to fit in along the sides and corners of the chimney. Place some silicone sealant in the exposed areas of the corners of the chimney. Nail the flashing in place. The shingles should also overlap the flashing in these sections. Install the rest of the flashing in the same manner, working your way right around the chimney. Make sure the shingles overlap the flashing and the sealant is applied to any gaps.

Step 3 - Install the Chimney Saddle

The chimney saddle will help excess rain water to run off the roof. This should be installed at the back of the chimney, and the metal flashing will also need to be installed around the base of this as well. Attach the chimney saddle in place using the same galvanized roofing nails.

Step 4 - Install Cap Flashing

caulking flashing around a chimney

The top of the cap flashing needs to be installed into the chimney. For this, grooves of approximately an inch in depth need to be gouged into the mortar line of the chimney where the flashing will be installed. Use a circular saw or a grinder to make this groove.

Place the cap flashing at the front of the chimney after having cut it to size. Bend the sides of the flashing around the corners, and hammer it in place. Likewise, install the side flaps of the cap flashing, and fasten them in place with roofing nails. Cut and install the cap flashing sections for the sides of the chimney. and finally, cut and install the rear cap flashing. The sections should overlap each other by about two inches.

Step 5 - Apply Sealant

Apply the silicone caulk along all of the grooves to seal the installation and make it watertight.