Chimney Flashing

Is Your Chimney Or Roof Leaking? Does Your Chimney Flashing Need Repair?
For Answers Start Here!

Roofs can begin to leak long before the entire roof must be replaced. Sometimes it is caused by broken shingles or shakes, sometimes cracks appear due to weathering, many things can cause leaks. Chimneys can leak from the crown or the cover. Bricks may not be properly waterproofed. Often the leaks appear where the flashing meets the chimney. In fact, most chimney leaks are caused by improper or damaged flashing. Proper flashing is essential to prevent leaks in the area where the chimney and the roof meet. The beautiful look of a new roof or chimney can be ruined very quickly if the flashing is improperly installed.


What is Flashing?

Flashing is a metal material, most often aluminum, which covers the area where your chimney exits or connects with the roof. It must be of sufficient width to properly cover the area. It is also used in other places such as, the valleys where two roofs join together or any type of roof penetration. The purpose of flashing is to keep water from entering the joints.


What to Look for When Having Flashing Installed

As mentioned before, most chimney leaks can be attributed to improper installation of flashing. Let’s look at some of the reasons for improper installation:

  • Inexperienced installers often rely on tar and other underlayment as the primary waterproofing answer. The installer must use the correct materials for each situation to create a water-shedding system that will protect the roof throughout the years.
  • Experience counts! It is imperative that the installer knows the correct installation procedures for the type of roof and external wall materials used in the project. Lack of experience and skill can lead to seal failure in the future. Don’t be afraid to ask questions.
  • Many times building codes do not address flashing so contractors may not focus on it. It is imperative that contractors have the knowledge and training to install flashing properly.

Eventually all flashing fails and it will fail sooner than later if it has been installed using outdated products like tar. Ask your installer about the products he is using and request the best.


How to Look for Leaks

The first step to maintaining your roof and chimney is regular inspection. You may not notice a leak until you see a damp or darkened spot on the drywall inside your house. At that point the chimney may have been leaking for a long while and extensive damage could have occurred. Therefore, you should have the flashing and seals around your chimney inside and out inspected on a regular basis. Have the inspection done before winter sets in. You don’t want to discover a leak on a cold winter day when you’d rather be sitting by a nice, warm fire! If you aren’t experienced with working on a roof, you should call an expert to do your inspections. A few things to look for are:

  • The flashing should extend at least 4 inches from the point where the chimney penetrates the roof. Anything less will eventually lead to leaks.
  • The area on the back of the chimney is called the back pan and is the most susceptible to leaks. This area is vulnerable because if the flashing is installed improperly water, snow and leaves can accumulate and lead to leaks. Properly installed flashing provides a way for the water and snow to easily clear the area.

All flashing MUST be installed using the proper technique for each type of exterior finish. This may add extra expense, but it guarantees a proper waterproofing system. In the long run, proper installation saves money! The five most common types of exterior chimney finish are brick, vinyl siding, wood board, stucco and cinder block. Each of these finishes has their own specific processes for attachment of flashing. Counter flashing must be mortar on the outside of brick, ventilation of vinyl siding is important, wood board tends to crack and split, stucco must be redone each time flashing is installed or repaired, and a specific type of flashing called gum lip must be used with cinder block.


Other Causes of Chimney Leaks

If your chimney is uncapped, rain can fall straight into the chimney, weakening the mortar in brick chimneys and causing rust as well as other problems. A cap will keep water, snow, leaves and animals out of your chimney. The chimney crown can also leak if the cement is cracked. It should also be inspected regularly. A crack left untreated will only get worse. Chimneys can leak from the inside out due to condensation causing damage to drywall, paint and wallpaper. This can happen when a gas furnace is installed in the chimney but the chimney is not lined properly. Bricks and mortar can fail because they are exposed to the weather. Repeated freezing and thawing causes shrinkage and cracking, thus letting water leak into the chimney.



Virtually all leaks are fixable – if they are caught in time. Fixing them early saves time and money and is a great investment in the future of your home.


Safety First!

Never walk on a wet roof. Wait until it’s a sunny day and the roof is dry to have your roof inspected.

Make sure your inspector follows safety precautions such as wearing rubber soled shoes and using safety ropes.

Pay attention to the location of all power lines and telephone lines.