Roof Cap Installation for Sloped Roofs

Roof Cap Sizes

• To fit all roof vents, roof caps come in a range of sizes. The size of the opening in the vent that the roof cap must cover determines the size of the roof cap needed. For a roof cap to fit over, and fully cover, a roof vent opening, you must purchase a cap in the appropriate size. When purchasing a cap, don’t rely on the dimensions of the cap alone. Check the packaging to see what vent sizes the cap is designed to cover.

Trimming the Vent

• Before you place a roof cap over a vent, you must trim away some of the vent to ensure it fits beneath the roof cap. The bent pipe should be cut so that the top sits at the same angle as the roof, instead of straight across, and only an inch or so of the vent should extend above the roof. Once the vent has been trimmed to this size, most roof caps should fit over the opening.

Keeping Out Birds

• You should take steps to ensure that birds and other critters have no means of entrance into your home through a roof vent before installing a roof cap. This can be accomplished using a bird screen. Get a bird screen cap the same size as the vent opening and slide the cap over the top of the vent. Alternately, cut wire mesh down to the size of the opening and use wire to secure it around the top of the vent.

Installing the Roof Cap

• Once the vent is prepared, install a roof cap by placing the cap down in front of the vent and sliding it upward on the roof so that it slips beneath the singles above and on either side of the vent. Where the shingles meet the roof cap base, apply roofing cement to create a tight seal that keeps water and debris out. On the bottom of the roof cap, where the base remains exposed, drive nails through each visible nail hole in the roof cap and cover the heads of each nail with cement.