How to Install Your Chimney Cap

The manufacturers instructions will give you the best information on how to install your specific model, so if your chimney cap came with instructions be sure to follow those rather than the guidelines below.

In order to avoid rain damage to your flue and rodents building nests in your chimney you need to have a chimney cap. After you have found the correct measurements and ordered your cap, you need to think about how you are going to install it. Here are a few simple steps to assist you with installation.

The manufacturers instructions will give you the best information on how to install your specific model, so if your chimney cap came with instructions be sure to follow those rather than the guidelines below.

You will need to wear protective gloves when you are installing your chimney cap as it is made from metal that could have sharp edges.

Outside mount chimney caps are relatively easy to install. Simply place the cap over the flue, making sure to cover the top 2 to 3 inches of it. Next you will use screws to tighten the chimney cap down on all sides.

For an inside mount chimney cap you can achieve a tight seal by pushing it down the flue. You can then use a silicone sealer to cover the joint.

If you have a metal flue and are installing an inside mount chimney cap you will want to push the cap down into the flue. In this case you will want to avoid using silicone sealer as it can be ruined by the heat conducted by the metal flue.

Often all the items you need are shipped with the chimney cap, everything from sealer to Tapcon screws. For top mount chimney caps you can use either Tapcon masonry anchors or adhesive.

Should you choose to use adhesive, you first need to place the chimney cap in the correct location on the chimney crown. The flange of the chimney cap should then be bent so that it conforms to the crown. A line should then be drawn around the perimeter of the flange. A 3/8” line of sealant should be placed just inside the line. With a caulking gun you should create a loose wavy line about one inch thick. The flange should then be pressed down into the bead of adhesive. A putty knife could be used to remove and smooth any material that escapes as you press the flange down, but this step is not required.

Another way to install a top mount chimney cap is with Tapcon masonry anchors. To use masonry anchors you will need to have a 3/16” masonry bit and enough Tapcon screws to mount the chimney cap. Most hardware stores carry Tapcon kits that contain both the bits and the screws. You should use screws that are 1 ½" or 1 ¾" long and ¼” in diameter. You will need to place at least one screw on each side of your chimney, with a screw at least every runny foot. For example a chimney cap that is 17 by 24 inches will require the following configuration. One screw should be in the middle of each 17 inch side. On the 24 inch side you will place one screw on each end and one in the middle.

When you are ready to install you will want to place the chimney cap in the correct location on the chimney crown and then bend the flange around the crown. You will use a 3/16" masonry bit to drill holes through the flange and into the chimney crown. Loosely place a screw in each hole as it is drilled to hold the chimney cap in place. When you finish will all the holes be sure to tighten.