Install Metal Roof Flashing for a Skylight

Lead Image
  • 4-8 hours
  • Advanced
  • 500-800
What You'll Need
Tape measure
Metal cutter
Ply board
Caulk gun
Caulk tube
Metal flashing
Roofing nails

Although roof flashing is merely the addition of a flattened galvanized steel or aluminum sheet over joints in the roof, it plays a critical role in the defense against water leaks. It is found attached to plumbing vent stacks, chimneys, fan vents and roof valleys. Roof flashing is water-resistant, low-maintenance and can carry weight or accommodate movement. Mistakes in the installation of roof flashing will allow water to seep into the interior of the house and may lead to costly damages. Follow the simple steps below to properly install metal roof flashing for your skylight.

Step 1 – Determine How Much Roof Flashing You Need

To keep costs down, first determine how much roof flashing you actually need. You will need one roof flashing for each side of your skylight. Measure the length and the height of the sides of the skylight. The more sides and the longer your skylight has, the more roof flashing you will need.

Step 2 – Prepare the Metal Flashing

Cut the metal flashing based on the length you determined, but adding an extra two inches. When the piece is cut, mark the height of the skylight, add one inch and cut. For ease of installation, bend the cut piece of flashing to about 85 degrees. Do this by inserting the flashing between two boards with the cut edge aligned to the edge of the boards. Bend the extra portion of the flashing by pressing it against the overhang with the use of a third board. Repeat these steps until you have all the metal flashings that you need.

Step 3 – Install the Metal Flashing

Once the metal flashings are ready, place the pieces between the roof and skylight, above the roof and under the skylight. Secure by nailing the flashing to the roof. Then fold the tabs on all sides of the skylight and screw them down. Repeat to install the flashing to all sides of the skylight frame.

Step 4 – Cover the Gaps

Once all the metal flashing has been securely fastened on the roof and sides of the skylight, ensure that there will be no avenue for water to seep in. Cover seams and gaps formed in between flashings by caulking these spots. Spread the caulk evenly to make sure that all spots are fully covered. Unless this part is well done, then the purpose of roof flashing will be forfeited.