How To Install Roof Flashing

If you've recently built an addition to your home, you'll need to install roof flashing to connect the old and new roofs as well as in the roof valleys. Proper flashing installation is an important feature that allows rainwater to run off both the house roof and porch roof properly. The flashing should be installed before the roofing material. Follow these few simple steps for a successful installation project.

Step 1- Measure the Flashing Needed

Make careful measurements and purchase your flashing from a local home improvement center or roofing supply store. Aluminum is the most popular flashing material choice. However, you can choose tin (20 to 40 pound weights), galvanized metal, sheet lead and premium copper. Allow for about a 10-15 percent over run. Flashing normally comes in 10-foot lengths, so purchase enough to cover the entire project plus a little left over in the event you make a mistake cutting or measuring.

Step 2 – Prep the Area

If making a valley roof repair, remove all materials down to the roof planking before installing flashing. Makes sure the valley area is clean and dry before proceeding. If attaching a room addition to an existing roof, remove a line or two of shingles on the original roof. You don’t need to remove any tar or felt paper. However, you might want to consider removing the top siding on either the house or room addition before flashing installation.

Step 3 – Cut and Bend the Flashing

Cut the flashing material to the desired length. When tying in two roofs, bend the flashing in the middle using a metal break tool according to the roof joining angle. Flashing is normally eight inches wide, so make sure each roof has four inches of flashing material.

Step 4 – Lay Flashing Down

Place the flashing where needed lining up the middle of the flashing with the valley grove. If tying in two roofs, make sure half of the flashing is on both sides.

Step 5 – Secure Flashing

Use a heavy duty staple gun to secure the flashing to the roof planking applying the staples one-inch from the flashing edge down each side of the material.

Step 6 – Replace Roofing

Once you’ve installed the flashing in a valley, replace the roofing material to ensure a waterproof barrier. Finish the roofing for the two tie-ins also installing fascia board.

Step 7 – Tar Application

Use a little roofing tar for extra added protection against water back-up before installing shingles.

Things to Remember

Single pieces of flashing can be used in place of one long one if these are overlapped carefully by about two inches. Do not use aluminum if you plan to join multiple pieces of flashing by soldering these together. Aluminum cannot be soldered so you need to use another material like tin or galvanized metal. Remember to always wear gloves and protective eyewear to ensure safety.