Understanding the Importance of Chimney Flashing

If your chimney extends through your roof or any part of your roof’s overhang, the flashing system plays a vital role in its integrity. Chimney flashing consists of sheets of durable materials, such as sheet metal, meticulously installed to create a barrier against water intrusion from the expansion space surrounding your chimney.

This expansion space allows your chimney to accommodate temperature changes when it heats up during fireplace use. The two components of flashing—roof flashing and chimney flashing—work in harmony, ensuring that your chimney can expand and contract while effectively keeping your roof watertight.

The roof flashing is installed from beneath the roofing material, bending up and under the chimney flashing. The chimney flashing, on the other hand, extends from a joint at the chimney’s base, bending down to overlap the roof flashing. Together, these components prevent rainwater from leaking into your home.

Even if your chimney has flashing, it may still be inadequate, potentially leading to interior leaks. As depicted in the images below, these issues can persist, highlighting the importance of proper chimney flashing installation and maintenance.

The Consequences of Deteriorating Chimney Flashing

When the chimney flashing deteriorates, it creates a pathway for water to infiltrate the interior of your home. This can result in substantial damage to the roof and walls in the vicinity of the chimney, as vividly illustrated in the picture below.

Step Flashing: A Common Chimney Flashing Type

Step flashing, named for its resemblance to steps on a chimney, is a common type of flashing used in many chimneys. However, we typically advise against its installation due to its vulnerability to being dislodged by strong winds or other service personnel walking on your roof. This can compromise its effectiveness in preventing water intrusion.