If your roof leaks, often the flashing is to blame. Flashing is used to protect seams in your roof, funneling water away from areas where it could penetrate the roofing. Over time, the flashing can deteriorate, or it could have been installed incorrectly in the first place. You can repair the flashing yourself if you are comfortable being on your roof and have a basic knowledge of roofing.
Step 1: Use a wire brush to remove any rust from the surface of the flashing, sand the area too if necessary. With a metal edged putty knife, remove any old caulk or loose roofing cement.
Step 2: Wash the flashing with a mixture of trisodium phosphate and water. Be sure to wear gloves when cleaning with TSP.
Step 3: Apply a rust converter/primer to any rusted surface. Apply two coats, allowing for proper drying time between coats of rust converter. Once the primer is dry, paint the primed areas with latex paint to conceal the repair.
Step 4: Look for areas where the flashing is no longer firmly attached to the roof or adjacent areas. Use flashing adhesive and a putty knife to put the adhesive underneath the flashing. Press into place firmly: you may want to use a brick to hold the flashing into place until the adhesive cures.
Step 5: Apply roofing cement to the edge of the flashing and extend it to cover the seam. Use a putty knife to spread the roofing cement and ensure that the edge is properly sealed. Be generous with the application of roofing cement and be sure to cover all seams. Allow the roofing cement to dry before continuing.
Step 6: Paint the flashing with rust resistant latex paint to protect it from further deterioration.