Repairing a Leaky Chimney

A fireplace can be a truly marvelous thing. They are usually the centerpiece of any living room they happen to be in. A fireplace provides ambiance, warmth, and mood, all while lowering your heating costs. But, to have one you must also have a big hole in your roof. This is where the potential for trouble comes in. This article will discuss the basics of getting a good, weather tight seal around your chimney.

When dealing with roof leaks, place flashing high on the list of usual suspects. It is the most common thing to go awry, and chimney leaks are no different. Flashing is sheet metal that keeps the transition between the chimney and the roof watertight. If water manages to get behind the flashing, it can do extensive damage to the roof decking, framing, and even the interior of your home. You will want this fixed immediately, in order to avoid expensive repairs.

To properly install flashing will require two layers. The first layer is called step flashing. L-shaped sections of sheet metal are woven into the shingle courses and lapped up the side of the chimney. The next layer of metal (counter-flashing) should be imbedded in the mortar joints of the chimney and folded down to cover the step flashing.

Even if installed by a skilled professional the corners will need a bit of extra attention. As the metal is cut and bent around the corners it leaves a very small gap that should be sealed with a quality urethane caulk. Please note that extra caulk is not a viable substitute for quality flashing work.

There are quite a few different metals used as flashing. Aluminum and galvanized steel are two of the most common types. Copper is available, and lasts a very long time, but as you may have guessed it also happens to be very expensive. Lead is also used, and its malleability makes it rather easy to work with.

If a chimney happens to be located at the bottom of a roof slope, it may be a good idea to build (or have built) a cricket. A cricket is a small diversion roof built on the high side of the chimney. This roof helps keep the flashing from being slammed against by water rushing down the length of a roof slope.

It is a very good policy to inspect the seal around your chimney every year or two. Look for missing or damaged flashing, as well as cracks in the masonry. Small cracks can be caulked with a masonry specific caulk. Some builders even recommend spraying the chimney with a silicone based sealant to keep moisture from soaking into the brickwork.

I’d like to mention again the importance of quality work. Do not attempt to fix a problem on your own without the proper tools, and know-how to get the job done right. The money saved by doing it yourself can be very small compared to repair costs stemming from improperly installed flashing.