Short answer: The ten signs are loose or rusted step flashing, counterflashing pulled from its mortar joint, a single bent piece of metal instead of proper stepping, caulk substituted for flashing, cracked or missing sealant at a counterflashing reglet, no cricket behind a wide chimney, water pooling behind the chimney, visible rust or daylight gaps, attic staining below the chimney, and old flashing left in place during a roof-only replacement.
How Chimney Flashing Works, and Why It Fails First
Flashing is the metal system that seals the joint where a chimney passes through a roof, and it is one of the most common leak points on a house, not because the metal itself fails often, but because it is frequently installed poorly, caulked instead of properly stepped, or never renewed when the surrounding roof was replaced.
A chimney moves independently of the roof around it, settling and expanding at a different rate than the framing and shingles. Flashing is the detail that has to absorb that movement while still shedding water, which is why it is built from layered, overlapping metal rather than a single sealed joint.
A correctly built system uses step flashing woven into the roofing courses against counterflashing set into or over the masonry, so water sheds in layers no matter which direction it is running. Every sign in this guide is a version of that layered system breaking down at one specific point, which is also why flashing problems are frequently mistaken for a roof leak or a chimney leak when the actual failure is neither — it is the joint between the two.
This guide focuses on flashing specifically. For brick, mortar, crown and cap problems, see our companion guide on signs you need chimney repair.
Step Flashing Pulled Loose, Rusted, or Never Properly Stepped
Step flashing is the series of individual L-shaped metal pieces woven into each course of shingles along the side of the chimney, overlapping the piece below by at least three inches. Pieces that have pulled loose, rusted through, or were installed as one continuous bent sheet instead of true steps are a common and largely invisible-from-the-ground failure point.
| Sign | What it means |
|---|---|
| Individual step pieces missing, loose or rusted | Water can enter at that course regardless of how the rest of the flashing performs |
| One continuous piece of metal bent around the chimney | Not true step flashing; it cannot move with the roof and typically fails at the bends |
Roofing manufacturer installation guidance is specific about the overlap: each piece of step flashing should overlap the one below it by at least three inches, and should stay hidden beneath the shingle top lap rather than showing on the roof surface. When a roofer installs a single bent piece of aluminum around the chimney instead of individual stepped pieces, it looks similar from the ground but cannot flex with the roof the way true step flashing does, and it typically starts leaking at the bends within a few seasons.
Where to look
From inside the attic, step flashing failure often shows as staining on the rafters or sheathing directly beside the chimney, at the same height as the roof plane outside. From the ground, look for daylight, gaps or visibly lifted metal along the sides of the chimney where it meets the shingles.
Counterflashing Pulled Loose From Its Mortar Joint
Counterflashing is the upper layer that overlaps step flashing and is set into a reglet cut into the mortar joint of the chimney itself. Counterflashing that has pulled loose, was never properly embedded, or was disturbed during a prior repointing job is one of the more common flashing failures we find on Bergen and Passaic County chimneys.
Counterflashing does the opposite job of step flashing: instead of shedding water off the roof, it keeps water from running down the chimney face and getting behind the step flashing beneath it. Because it is set into the masonry rather than nailed to the roof deck, it is vulnerable any time the mortar around it is disturbed, which happens most often during a repointing job that skips resetting it correctly.
A counterflashing edge that has come away from the brick, even by a small amount, gives wind-driven rain a direct path behind the entire flashing system. If a chimney has been repointed recently and a flashing leak shows up afterward, disturbed counterflashing is the first thing worth checking, ahead of assuming the repointing itself failed. See our chimney repair page for how repointing and flashing work together.
Caulk or Sealant Standing In for Metal Flashing
Sealant applied along the flashing line, whether smeared over a gap in the metal or used instead of a properly cut counterflashing reglet, is a maintenance product, not a permanent flashing repair. Caulk has a service life measured in a few years at most, and once it cracks, shrinks or separates from either surface, the gap it was hiding is exposed again.
A bead of sealant along a flashing joint is not automatically a red flag by itself — some sealant is a normal part of a correctly built system. The problem is caulk used as the primary water seal in place of the metal itself, which is a shortcut some installers take instead of cutting a proper reglet or fabricating stepped pieces.
- Sealant that has visibly cracked, shrunk away from the brick, or turned chalky and brittle has already failed as a water barrier.
- A wide bead of caulk running the entire length of where metal flashing should be is a sign the flashing detail was skipped entirely.
- Sealant reapplied year after year in the same spot means the underlying detail was never actually fixed.
Sealant has a legitimate, limited role finishing the edge of correctly installed metal flashing. It is not a substitute for the metal, and repeated caulk-only repairs at the same spot are the clearest sign that the real flashing detail still needs to be built correctly.
Missing or Undersized Chimney Cricket
A cricket, also called a saddle, is a small peaked structure built behind a chimney to divert water and debris around it instead of letting it pool against the uphill side. Under the residential code New Jersey enforces, a cricket is required whenever a chimney’s dimension parallel to the ridgeline is wider than 30 inches and it does not intersect the ridge.
Water and debris naturally collect on the uphill side of any chimney wide enough to dam the roof’s drainage path. A cricket redirects that flow around both sides of the chimney instead of letting it sit against the brick and the base of the flashing, which is exactly where standing water does the most damage over time.
New Jersey’s adopted residential code sets the 30-inch threshold specifically, with cricket dimensions sized to the roof’s actual slope. A wide chimney with no cricket, or with one built too small for the roof pitch, will show it as standing debris, moss growth, or persistent dampness on the uphill side of the chimney base — worth checking any time a roof is being replaced around an existing wide chimney.
Standing Water, Debris, or Moss Behind the Chimney
Leaves, granules and moss that collect and stay damp on the uphill side of the chimney, rather than washing down with the rest of the roof, signal that water is not draining the way the flashing and roof design intend. This is often visible from a ladder or from an upstairs window without needing to walk the roof.
A properly flashed and cricketed chimney sheds debris downhill with the rest of the roof surface. Debris that consistently piles up and stays wet on the uphill side, instead of washing clear during normal rain, means water is pooling there rather than draining, which is the same condition a missing cricket or failed flashing produces.
Moss growth in that specific spot, when the rest of the roof is clear of it, is a strong secondary confirmation, since moss needs sustained moisture that a properly draining roof surface does not provide even in a wet climate.
Rust Streaks, Corrosion, or Visible Gaps in the Metal
Orange or reddish-brown streaking below the flashing line means the metal itself is corroding, usually galvanized steel that has lost its protective coating or flashing that was never designed for the exposure it is getting. Visible gaps, lifted edges, or daylight showing through the flashing line are a more advanced version of the same failure.
Different flashing metals corrode differently. Galvanized steel rusts once its zinc coating wears through, while aluminum tends to pit and develop white corrosion rather than orange rust. Either way, corrosion streaking down the brick or shingles below the flashing line is a sign the metal has already been compromised, not an early warning of something that might happen.
Gaps or daylight visible along the flashing line, whether from a ladder or with binoculars from the ground, mean the physical barrier has a hole in it right now, not just a weak point. That level of damage typically needs a full flashing replacement rather than a patch, since the corrosion is rarely contained to only the section that is visibly failing.
Attic Staining or Roof Deck Damage Near the Chimney
A stain on the attic sheathing or rafters near where the chimney passes through the roof, or plywood that has gone soft or discolored in that specific area, is often the first hard evidence of a flashing failure, since it shows up before any sign is visible from the ground or the roof surface.
Flashing problems are frequently discovered from the inside before anyone notices anything from outside. A flashlight check of the attic near the chimney, especially after a heavy rain, often finds staining, dark streaking, or soft sheathing well before a corresponding sign shows up on the roof or the ceiling below.
Because water can travel along a rafter or truss before it drips down, the wet spot in the attic is not always directly beneath the leak point at the flashing — it is worth tracing the stain uphill toward the chimney rather than assuming the nearest point of the flashing is the source. Our roof repair crews and chimney crews investigate this together, since the two trades share this exact detail; see our roof repair page.
Old Flashing Left in Place During a Roof-Only Replacement
Flashing that is decades old but was never replaced during a roof tear-off, because it was caulked over instead of pulled and renewed, is a deferred failure waiting to surface. New shingles installed around old flashing look complete but inherit whatever condition that flashing was already in.
A full roof replacement is the easiest and least expensive time to renew chimney flashing, because the shingles around it are already being removed. Skipping that step to save time on the tear-off is a shortcut that shows up later as a leak on an otherwise brand-new roof, and one that is harder to diagnose because homeowners reasonably assume new roofing means new flashing.
If your roof was replaced within the last several years and you are now seeing any of the signs above, ask whether the original chimney flashing was pulled and replaced at the time, or caulked and reused. That single detail explains a surprising number of leaks on roofs that are otherwise still under warranty.
Getting Flashing Fixed Before It Becomes a Roof Leak
Any one of these ten signs is worth a hands-on look, because flashing problems compound quietly until they show up as a ceiling stain or a soaked attic deck. NJ Gold Star Construction inspects and repairs chimney flashing across Bergen and Passaic County alongside our roofing work, with a free written estimate before anything starts.
One customer described the process after a roof and chimney project handled together: “the whole process was explained in depth before the job was started. The crew was professional, NO nonsense, straight to work, completed on time.” — Bill E., Google review.
We handle chimney flashing, repointing and rebuilds across the service area, including Hackensack and Teaneck, and our guide on common roof leaks and how to fix them covers the roofing side of this same joint. See the full chimney repair, rebuilds and cleaning overview, or request a free written estimate.
Frequently asked questions
How long does properly installed chimney flashing last?
Quality metal flashing, correctly stepped and counterflashed, commonly lasts as long as the roofing around it, with the exact service life depending on the metal used. Flashing fails early far more often from poor installation, such as caulk substituted for step flashing or counterflashing left disturbed during repointing, than from the metal itself simply wearing out.
Can I just add more caulk to a flashing leak myself?
Sealant can buy a little time on a small gap in otherwise sound metal flashing, but it does not fix a missing cricket, corroded metal, or counterflashing that has pulled out of the mortar. Repeated caulk applied to the same spot year after year is usually a sign the underlying flashing detail needs to be rebuilt, not resealed again.
Does every chimney need a cricket?
No. Under the residential code New Jersey enforces, a cricket is required specifically when a chimney’s dimension parallel to the roof ridge is wider than 30 inches and the chimney does not intersect the ridge itself. Narrower chimneys, or ones built directly at the ridge, are exempt from that specific requirement.
Is a flashing leak covered by roofing warranties?
It depends on the warranty and whether the flashing was installed as part of the covered roofing work. Many manufacturer warranties cover the shingles but treat flashing installed incorrectly, or flashing left in place from a prior roof, differently. Check the specific terms of your roof warranty rather than assuming flashing is automatically included.
How can I tell if a leak is from the chimney flashing or the chimney masonry itself?
A flashing leak typically appears as a stain that traces back to the roofline where the chimney meets the shingles, often worse during wind-driven rain. A masonry leak from a cracked crown or open joint tends to appear higher up, closer to the top of the chimney, and can show up even in a light, straight-down rain with no wind.
Should flashing be replaced every time a roof is replaced?
It should at least be inspected and, in most cases, replaced rather than reused. Flashing removed intact during a tear-off has already been through years of thermal movement and corrosion, and reinstalling it under new shingles just resets the visible surface while leaving the underlying wear in place.
Sources
- Chapter 10 Chimneys and Fireplaces: New Jersey UCC One- & Two-Family Dwelling Subcode 2021 (Section R1003.20) — UpCodes (New Jersey edition of the 2021 IRC)
- Chapter 9 Roof Assemblies: New Jersey UCC One- & Two-Family Dwelling Subcode 2021 — UpCodes (New Jersey edition of the 2021 IRC)
- How to Install Shingles: A Step-by-Step Roof Shingle Installation Guide — IKO Industries
- Chapter 7 Wall Covering: New Jersey UCC One- & Two-Family Dwelling Subcode 2021 (Section R703.8) — UpCodes (New Jersey edition of the 2021 IRC)
- Homeowner Resources — Chimney Safety Institute of America (CSIA)
Have a question about your own home? Call (862) 271-1225 or request a free written estimate.