Learning how to install a chimney cap involves some basic DIY skills. Even so, this job should only be completed by individuals who know how to work on roofs safely. Access your roof with an extension ladder long enough to reach 3 feet beyond the eave. You should wear nonskid shoes and use a safety harness, especially if your roof is steep.

How to Install a Chimney Cap Directions

For a single-flue chimney:

1. Position your ladder on stable ground and mount the roof.
2. Attach your roof harness if using one.
3. Measure the flue of the chimney, which is the clay or metal tube extending upward from the chimney structure.
4. Find the length and width of the flue and write down the dimensions.
5. For circular flues, measure the diameter.
   1. Wrap the measuring tape around the flue to measure the circumference.
   2. Enter the circumference figure into an online circle calculator to find the diameter.
6. Buy a chimney cap that fits the flue.
   1. Choose a galvanized steel cap if you can find one.
7. Return to the roof and lower the cap onto the flue.
8. Position the cap so that it is at least 6 inches from the top of the flue to ensure proper release of exhaust fumes.
9. Use a screwdriver to drive the included self-tapping screws through the cap’s rim holes into the flue.
10. Tighten screws until they hold the chimney cap firmly in place.
11. Alternatively, some caps come with a clamp that you will tighten around the flue.

For a multi-flue chimney:

1. Safely mount your roof and measure the flues as a single unit.
2. Determine the width, length, and height that will cover all flues and leave 6 inches above tallest flue.
3. Measure the width and length of the chimney crown around the flues.
4. Scrub clean the crown with a stiff-bristle brush.
5. Buy a chimney cap that will fit your dimensions.
6. Mount the roof and set the cap over the flues and onto the crown.
7. Fit a power drill with a masonry bit that is 1/8 inch smaller than the installation screws.
8. Drill pilot holes into the crown through the holes on the cap.
9. Remove the cap and run a bead of caulk around the crown’s edges.
10. Set the chimney cap in place again over the caulk.
11. Place the installation screws in the pilot holes and tighten them with a screwdriver.