What is chimney flashing and how does it work?

When we think about important parts of a chimney the first things that come to mind are usually the bricks, the construction, and the mortar lined joints. These parts are all integral to the function of the chimney but there is another piece that is also very important and that piece is the flashing. Flashing lines the bottom edge of the chimney and, when it is installed and functioning properly, prevents water from entering the house via gaps between the roof and the edge of the chimney. This is typically done using two courses of flashing; The base and the counter. The base flashing is embedded in the shingles and bent upwards. The counter flashing is embedded in the mortar. Here are some photos of flashing that will fail or has already failed (leak:)

Flashing needs to be tight up against the chimney. The corners need to be wrapped or tight and caulked. Here is a video of a proper flashing job we performed on a chimney and a skylight :

Contact us for your chimney cleaning and repair needs. We service the Portland, Oregon metro area; (503) 653-3819. CCB# 193902.

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About the Author:

A 24-year veteran of the chimney repair trade, Cliff has experience in most phases of chimney construction and repair. He began as a chimney sweep apprentice in 1991. Two years later he began to educate himself in bricklaying and chimney construction. He claims that "it has been an interesting trade to say the least.