Can I use copper flashings with a new cedar shingle roof?
A You can as long as you avoid line corrosion, which tends to occur where the shingles overlap the copper flashings. You can avoid this problem by raising the butt ends of the shingles off of the copper slightly with a small cant or hump incorporated into the flashing. This tactic keeps the tannic acids that get washed out of the shingles from dwelling on the copper for too long and corroding it along the butt line of the shingles. Even so, unsightly bright spots will appear in the copper wherever water drips off of the shingles. The bright spots represent areas where a patina is unable to form on the copper and where it will wear at an accelerated rate. There are better choices. Follansbee’s stainless steel sheet coated with a zinc-tin alloy (TCS II and TCS Satin) and Revere’s copper sheet also coated with a zinc-tin alloy (FreedomGray) are both appropriate for use with cedar shingles and will wear somewhat more consistently. The same is true of a lead-coated copper roof, although inc
