How to Attach a Flue Cap to Your Chimney

What You'll Need
Flue cap
Caulking gun
Putty knife
Protective gloves
Soft rag

A flue cap is a vital chimney feature that assures you of greater chimney efficiency. A properly installed chimney cap will add to the longevity of your chimney. You may install it during initial construction of your home or at any other time. Fitting the cap onto the flue is not a complicated process. It is a job you can comfortably undertake yourself. Below is a guide to help you attach your flue cover.

Step 1 – Mount the Roof

Use a ladder to get onto your roof.  Be sure to carry all the installation items with you. This will make it easier to complete the work without having to climb down for required items.

Step 2 – Fit Cap onto Flue

Place the flue cap at the desired position on the chimney crown. The crown is the concrete portion of the chimney that surrounds the flue. Adjust the cap so that it is well aligned. The entire base perimeter of the cap should be at a uniform level. Make the necessary adjustments should you notice one part of the cap at a higher level.

Step 3 – Conform the Flange

Bend the flange around the base of the cap so that it falls in line with the chimney crown.

Step 4 – Mark the Flange

Circle the flange with a piece of chalk. As you draw the circle, hold the cap down gently to prevent it from shifting out of place.

Step 5 – Lay Adhesive

Use the caulking gun to spread adhesive inside the marked line. 3/8s of an inch should do. Move the caulking gun in a zigzag pattern so that you make a wavy line of adhesive across the original marked line. Do not exceed 1 inch on either side of the middle line as you lay the adhesive.

Step 6 – Attach Flange

Firmly press the flange of the chimney cap into the adhesive. Be sure that the entire perimeter of the flange attaches onto the adhesive. This will ensure a secure fit. It is important that you maintain a uniform alignment of the flue cap as you work. You want to be sure that once the cap is attached, it does not look misaligned.

Step 7 –Smooth the Adhesive

Some adhesive may show through the holes in the flange. Use a putty knife to evenly distribute the adhesive. You may use a soft rag to wipe away excess adhesive.

Step 8 – Allow to Dry

Allow some time for the adhesive to dry completely before you use your fireplace.


  • Allow some space between the end of the flue liner and the bottom of the cap. If you set the cap too close to the flue, it will restrict the healthy flow of gases from the chimney.
  • Be sure to obtain accurate flue measurements. This will ensure that you purchase a cap that fits properly when installed.
  • Have someone stationed on the ground while working on the roof. This makes it easier to seek help should an accident occur.