How to Install Vent Pipe Flashing on an Existing Roof

Installing vent pipe flashing on an existing roof is not a complex project. Not only will it reduce potential water damage, but this simple job can save the homeowner hundreds of dollars down the line. To ensure that the installation is leakproof, however, it is important that the flashing and the adjacent shingles fit around the vent pipe properly. Common tools and a few simple steps will ensure a watertight seal when installing vent pipe flashing on an existing roof.

Step 1

Bend back the roofing shingles above and on the two sides of the vent pipe with a pry bar. Do not pry back the shingle beneath the vent pipe.

Step 2

Slide the new flashing over the vent and into position. Install the flashing under the top and side roofing shingles, but lay it above the roofing shingle that lies below the vent pipe. Turning the flashing as you lower it into place will make the installation easier. Be sure the neck, or hole, of the flashing fits snugly around the vent pipe.

Step 3

Hammer the roofing nails into the top and sides of the flashing sleeve, making certain the top and side roofing shingles are bent back so as not to nail through the shingles. Seal the nail heads with roofing cement.

Step 4

Hammer the roofing nails into the bottom edge of the flashing, making sure the flashing lies on top of the shingle located just below the vent pipe. Seal the nail heads with roofing cement.

Step 5

Seal around the edges of the flashing with roofing cement.


  • Use nails made of the same metal as the flashing material. Dissimilar metals may react with one another, hastening corrosion.

About the Author

Susan DeFeo has been a professional writer since 1997. She served as a community events columnist for New Jersey's "Cape May County Herald" for more than a decade and currently covers the family and pet beat for CBS Philadelphia. Her health, fitness, beauty and travel articles have appeared in various online publications. DeFeo studied visual communications at SUNY Farmingdale.