As a NJ home inspector, I spend a lot of time on roofs or looking at them from a ladder. One of the most common sources of water entry I find is around chimneys. In most cases, the problem is with the chimney flashing.
Chimney flashing is the metal that seals the gap between the roof and the sides of the chimney. It is there to keep water from running down into the roof structure. When it is missing, installed wrong, or falling apart, water will find its way inside. Over time, this can lead to rotted roof sheathing, damaged framing, stained ceilings, and even mold growth.
I inspect homes across New Jersey, and I can tell you this is one of those things that looks fine from the ground but tells a different story up close.
What chimney flashing is supposed to do
Flashing is designed to keep the joint between the roof and chimney watertight. It does this in two main parts:
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Step flashing along the sides that overlaps each course of shingles to direct water away from the chimney
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Counter flashing that covers the top of the step flashing and is embedded into the chimney mortar to create a seal
If done right, flashing will last many years. If done wrong or neglected, it becomes a water funnel straight into your home.
Common parts of chimney flashing that are missing or wrong
Over the years inspecting NJ homes, I have seen just about every way chimney flashing can be done wrong. Sometimes the problem is that certain pieces were never installed at all, other times the right parts are there but installed incorrectly. Both lead to leaks. Here are the main areas where flashing issues show up:
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Counter flashing missing completely – This is the metal that should be cut into the mortar joints and overlap the step flashing. Without it, water can get behind the step flashing with ease. Many times, I see just the step flashing with caulk smeared along the chimney. Caulk is not a long-term fix.
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Counter flashing not embedded into the mortar – Good counter flashing should be inserted into a groove cut into the mortar joint and then sealed. Too often, installers simply bend it up against the brick or stone and run a bead of caulk along the top. That caulk fails, and once it does, water pours in.
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Step flashing sections skipped or cut too short – Step flashing should be installed as individual pieces that overlap each shingle course along the chimney sides. Sometimes roofers take shortcuts and use long pieces or leave gaps, which defeats the purpose and leaves openings for water.
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Pan flashing missing at the uphill side of the chimney – On the side of the chimney that faces uphill, a single wide piece of flashing called pan flashing should be installed to collect water and direct it around the chimney. If it is missing or too small, water can pool behind the chimney and leak in.
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Apron flashing at the front poorly done or left out – At the downhill side of the chimney, apron flashing directs water out onto the shingles below. If it is bent poorly, rusted through, or not properly lapped under the shingles, it can allow water entry.
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Rust and corrosion eating through the metal – Older galvanized steel flashing will eventually rust, especially if the protective coating has worn away. Once rust holes form, leaks follow quickly.
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Roof cement patches covering flashing defects – I often find flashing buried under layers of black roof cement. This is a red flag that someone tried to mask a problem rather than fixing it. These patches crack, dry out, and fail, usually within a few years.
Even one of these issues can let water in. When two or three are combined, the leak can be severe and may go unnoticed for months or years until interior damage becomes obvious.
What I look for during a NJ home inspection
When I am inspecting a chimney, I look for:
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Missing or poorly installed step and counter flashing
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Rusted or corroded flashing pieces
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Evidence of water stains or rot around the chimney inside the attic
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Roof cement patches or other signs of past repairs
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Mortar joints where counter flashing should be embedded but is not
I also look for related problems like damaged chimney crowns, missing caps, and deteriorated mortar. These can make flashing issues even worse.
How to fix chimney flashing problems
If flashing is installed wrong, it usually needs to be redone properly. That means removing the old flashing, cutting a proper groove into the mortar joints, installing step flashing along each course of shingles, and securing counter flashing into the mortar with sealant.
In some cases, replacing the flashing can be done without replacing the roof. But if the roof is near the end of its life, it makes sense to do both at the same time.
Final thoughts from a NJ home inspector
Chimney flashing is not something most homeowners think about until there is a leak. The problem is that by the time you see water inside, the damage is already done.
During a NJ home inspection, I check chimney flashing closely because it is such a common cause of water damage. If you are buying a home, do not assume the chimney flashing is fine just because the roof looks okay from the ground. A proper inspection can save you from expensive repairs later.
John Martino is a NJ home inspector with over 25 years of experience inspecting homes of every age and style. He only does one inspection a day so he can focus fully on the property, take detailed photos, and provide a thorough written report. John’s inspections are known for being detailed, straightforward, and easy to understand. Learn more at www.looksmarthomeinspections.com.