Chimney Flashing 101

An Overview Of Chimney Flashing

Whether it’s happening in the basement or the attic, moisture is your home’s worst nightmare. Moisture from a leaky chimney is especially alarming as the problem is often difficult to detect and costly to repair. Excess moisture from a leaky chimney can also result in:

• General damage to wallpaper, paint and special finishes such as plaster
• Wood rot, which attracts pests such as rodents, ants, and termites
• Spread of the leak throughout your home
• Dangerous mold growth
• Ceiling stains

So what causes a chimney leak? Deteriorating mortar, missing chimney caps, or even insufficient venting are common culprits. But in our over 40 years of business in the roofing industry, we’ve found that faulty or improperly installed chimney flashings are the most common.

What is Flashing?

Flashing forms a waterproof seal between your roof and your chimney. With proper installation and regular inspection, flashing can last for up to 30 years or more. Types of flashing vary but typically depend on a few different factors including where you live, the size of your chimney and your roof’s material. Common flashing types include:

• Aluminum – Relatively inexpensive, aluminum can be installed on any type of roof. Aluminum is also a popular choice for contractors because it can be cut to fit any roof.
• Vinyl and PVC – Vinyl or PVC flashing is lightweight and common in areas of warm weather. Vinyl is brittle and susceptible to cracking, so it’s not recommended for areas that experience a lot of wetness or humidity.
• Steel and Galvanized Steel – Because of its durability and anti-corrosive properties, steel or galvanized steel flashing is a popular choice.
• Copper – Lightweight and durable, copper is one of the best types of flashing available. However, copper is expensive and can be cost-prohibitive to the average homeowner.

No matter the type of metal flashing used, it typically consists of two metal panel parts. The first part is called the step or base flashing. It’s installed underneath a shingle and bent upward against the chimney. The second piece of flashing is called counter flashing. This piece is bent down over the step flashing and embedded into the chimney mortar joint. Counter flashing seals off the top portion of the step flashing.

How is Flashing Installed?

When you hire a roofing company such as Community Roofing to install chimney flashing, the process may look a little like this:

1. Clear the chimney of any tar and existing flashing.
2. Inspect the deck around the chimney for loose wood and rot. If found, these are repaired.
3. Build a “cricket” or small peak at the back of the chimney. The cricket prevents water from hitting the chimney head-on by diverting it to either side.
4. Grind out all mortar joints needed to secure the counter flashing.
5. Secure the chimney with a moisture leak barrier.
6. Step flash the shingles around the side and back of the chimney.
7. Install counter flashing and mortar all joints.

Though the process may seem straightforward, proper chimney flashing installation requires the care, skill, and attention to detail that only an experienced mason can provide. At Community Roofing & Restoration, we employ several gifted masons who are have installed thousands of chimney flashings and are experts in their field. If you’re experiencing leaks due to faulty or improperly installed chimney flashing, then give us a call.

We approach every project like it’s our first – yours included. Visit our estimate page for your free estimate. Fill out our contact form today with any questions.