Small holes or corroded spots in flashing can be easily repaired. Renail loose nails, and cover nail heads with roofing cement. Plug pinholes with roofing cement, and patch holes up to about 3/4 inch in diameter with a patch from the same material as the flashing.

First roughen the area around the hole with a wire brush or sandpaper, and clean it. Cut the patch larger than the hole, affix it with roofing cement, and then cover the patch with more roofing cement.

Flashing that is badly corroded will need to be replaced. You will have to remove several rows of shingles as well as the old flashing to do this. Consider whether you have the skills and time to do this; otherwise, call a roofing contractor.

Renew flashing seals by chipping out the old mortar and caulking along the edges of the flashing. Use special masonry caulk to seal the joints between the flashing and chimney.

Seal the seam between the cap and step flashings with urethane roofing cement or silicone caulking compound. If you are working with valley flashing, lift the edges of the surrounding shingles, and spread roofing cement on the flashing about 6 inches in from the edge of the shingles.

If you are resealing drip edging, seal beneath the shingles, but don’t seal the drip edge along the eaves.

To replace flashing around the vent pipe, first remove the shingles covering the flange at the back and sides. Pry and lift off the flashing. Pull or cut off any nails. Position a new vent-pipe flashing over the vent, push it down into place, and nail where shingles will cover it. Replace the shingles, and cover the nails with roofing cement.

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