![]() ![]() We install asphalt shingles over the membrane to blend the cricket with the rest of the roof. We frame and sheathe crickets just like the rest of the roof, and then completely cover them with a modified bitumen membrane, which is folded up under the chimney flashing. When the chimney is at the bottom of a roof slope, we always install a cricket, a small diversion roof that prevents water from pounding the up-roof part of the chimney. But no matter which material is used, it must be layered correctly if water is to be kept out. In the Northeast, masons are partial to lead flashing, which is soft and easy to bend to shape. Another advantage to copper is that the corners can be soldered for a watertight connection. Copper is the longest-lived, but because it's expensive, we see it only on high-end jobs here. Aluminum and galvanized steel are the usual choices in the South where I live. The type of metal used for flashing depends on where you live. However, caulk is not a substitute for properly overlapped flashing materials. If the flashing looks to be in good condition, recaulking should take care of the problem. This caulk can work itself loose over time. Even in a quality installation, this leaves one small spot that should be sealed with a high-quality urethane caulk. We cut and bend the metal around the corner. Next comes the counterflashing: A second layer of metal is embedded in the chimney mortar joints and folded down to cover the top of the step flashing. The first is called step flashing: Sections of L-shaped sheet metal are woven into the shingle courses and lapped up the side of the chimney. Proper flashing around a chimney includes two layers. And more often than not, the culprit is the flashing - the sheet metal that keeps the intersection between the chimney and roof watertight. My firm gets more calls about leaks around chimneys than about any other problem. ![]()
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