Chimney Flashing

by | Dec 1, 2015

Have you ever noticed a brown or yellow discoloration on your ceiling? Has it grown over time? Does it look like the image posted below? If so, you may want to check to see if you have a roof leak. Don’t get me wrong, water leaks can originate almost anywhere, but with reference to this topic, I will be pointing out roofs specifically.

20151129_084847[1]Often times, when I am inspecting a house, I will look up and see a discoloration on the ceiling or the walls. When I see this, this first thing that comes to mind is a water leak. The roof is, arguably, the most important feature to the house. Without it, we may all be living out in the elements.

For the example I have pictured, I noticed a yellowish-brown stain on the ceiling next to a chimney on the upper level of a remodeled attic space. There could multiple reasons for this, but as an inspector, only one comes to mind first: Failed Counter Flashing.

Counter flashing is the metal collar that should be installed around a chimney in order to shield water or bulk moisture (rain) from invading the attic through the intentional hole built in the roof for the chimney itself. The reason this detail is referred to counter flashing is because it covers another important detail known as step flashing that prevents water that rolls down the roof slope from entering into the exact same hole, that would result in a roof leak. Step flashing is critical for the roof covering not to allow water into the structure where vertical structures abut the pitch of a roof (chimney or a vertical wall structure), but it is open at the top and will allow moisture behind it without some way to shield it from above. This is where counter flashing is so critical to water shed.

The counter flashing is installed, primarily, in one of two ways. A laborer would either cut a groove in the chimney bricks after the chimney was erected approximately 5-6 inches up from the finished roof covering and insert the metal flashing and secure it with mortar for a permanent installation, or the laborer would install this metal collar in multiple pieces (overlapping each metal piece horizontally) as he or she were constructing the chimney initially. This practice would negate the need for the groove to be cut after the chimney was finished being built.

Over time. when counter flashing eventually fails, a roof leak is not far behind. The counter flashing failure has multiple reasons for failing, but the two instances I see most are failure due to rust and failure due to bending or cutting. The rust is easy to understand, but how is it being bent or cut? This usually happens when a new roof is being installed, and the roofer installs the step flashing out of sequence and has to physically bend or cut the counter flashing because he or she forgot the re-install the step flashing into the new roof shingle covering.

Once either of the two examples above occur: NEXT STOP–> Sealant application

20151129_084820[1]In the picture provided, you can easily see why a leak developed in the roof, which then stained the finished ceiling below: Caulking. The sealant pictured is average, everyday, multipurpose caulking. When I say multipurpose caulking, I wasn’t implying every purpose. Caulking has absolutely no business on a roof covering. If you feel a sealant job is needed because of the aforementioned symptoms,  please, go to the hardware store and ask somebody in the roofing department. I would recommend roofing tar. It comes in a can or it comes in a tube identical to a caulking tube. It is usually black.

As you can see, the white sealant is applied along the top of the counter flashing where the collar meets the chimney bricks, and along the bottom where the  roof covering meets the step flashing. This application was done under the thought process of ‘I’m not sure why the roof is leaking, so lets just cover everything. We’re bound to fix it this way.’ When you are in a bind, sure, make the repair with sealant, but call a licensed roofer the next day and have a professional evaluate and repair. Your house will last longer, and you will be in a much healthier environment.