Flashing a chimney correctly involves two layers of metal: flashing and counterflashing. In this article, roofing contractor Dyami Plotke explains how he tackles each step in the flashing process. He almost always chooses copper for chimney-flashing jobs because of its appearance, endurance, receptiveness to soldering, and malleability. A series of three detailed drawings demonstrates Plotke’s steps. The first shows where to cut a groove in the masonry for the counterflashing, how to apply a peel-and-stick underlayment over the OSB sheathing patch and up the sides of the chimney, and how to install the apron. The second shows how to install the step flashing and the pan and includes Plotke’s methods for cutting and folding the copper at transition points to make the tightest fit. The third shows how to install the counterflashing. Before sealing the counterflashing to the brick, Plotke uses wedges of folded copper to hold the counterflashing in its groove, and copper pop rivets to connect the counterflashing on the up-slope edge to the counterflashing on the sides. On the up-slope side of large chimneys, he installs a copper cricket to shed water and snow.
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I was wondering if there is any slope to the copper pan that is installed behind the chimney? My house has a small chimney and I was under the impression that I should install a cricket. After reading this article, I'm now second guessing that. Any advice on the pan would be greatly appreciated. Would it be okay to install a small diverter right above the chimney to help direct water away even more? Thanks so much.