Chimney Flashing Leaks Repair: Causes, Fixes, and When to Call a Pro

Chimney flashing is one of the most leak-prone roof details, especially under New Mexico’s intense UV exposure, high winds, and monsoon rain. Because flashing sits around the chimney, even small gaps, cracks, or improper installation can let rainwater travel directly into the home.

When that happens, homeowners may notice a leaky chimney, ceiling stains, or moisture around the fireplace long before the true cause is obvious.

This guide explains what homeowners can safely inspect, diagnose, and photograph: the most common causes of chimney flashing leaks, the exterior warning signs, attic clues, and when chimney flashing leak repair by a professional roofing contractor becomes essential. These steps help protect the roofing system, the interior ceiling, and the home’s safety.

Common Causes of Chimney Flashing Leaks

Most chimney leaks don’t come from the chimney structure itself. Instead, they originate where flashing materials meet masonry chimneys, shingles, and siding. Below are the issues NM homeowners see most often.

1. Improper or Missing Step Flashing

A huge percentage of chimney flashing leaks come from improper installation of step flashing. Instead of using individual pieces that integrate with each shingle course, some roofers install continuous metal flashing.

While it looks smoother, this method doesn’t manage water flow correctly. Water slips behind the metal, causing water infiltration and water damage inside the attic.

Even one missing or old flashing piece is enough to cause significant damage. According to the 2021 International Residential Code (IRC) — R905.6.6 Flashing, proper step flashing and base flashing must be installed to ensure a good seal and long-term protection.

2. No True Counterflashing (Caulk-Only “Fake Flashing”)

Proper counter flashing must be cut into the mortar joints of brick or set into a siding kerf so it overlaps the step flashing below. Surface-mounted counter flashing with only a waterproof sealant is a temporary fix at best. Under NM’s intense weather and UV exposure, sealants tear, shrink, and lose adhesion.

3. Deteriorated Sealant and UV Fatigue

New Mexico’s sun accelerates the breakdown of caulk and sealant. At corners, reglet joints, and transitions, the material dries out every 3–7 years. Once it cracks, water leaking behind the system becomes unavoidable.

This is why even well-built masonry chimneys need regular inspections.

4. Rust, Pinholes, and Metal Corrosion

Older metal flashing often rusts at bends and nail holes. Homeowners may see rust stains running down a chimney wall or a damaged chimney face, an early sign of water intrusion.

Corrosion weakens the flashing, creating openings for rainwater and moisture that worsen each freeze-thaw cycle.

5. Reusing Old Flashing During a Reroof

A widespread problem in New Mexico: roof shingles get replaced, but old flashing remains. Fatigued metal, loose nails, and misaligned overlaps create pathways for water infiltration. This is why NRCA flashing best practices strongly discourage reusing flashing.

Sometimes, installing new step flashing is the only way to truly resolve a chronic flashing leak.

6. Missing or Undersized Chimney Cricket

Chimneys wider than about 30 inches on the upslope side need a properly sized chimney cricket to split and redirect water. Without one, rainwater and debris collect behind the chimney, overwhelming the step flashing and counter flashing.

This pooling creates constant moisture contact, increasing the risk of water intrusion, corrosion, and repeated chimney leaks, even when the rest of the flashing is installed correctly.

Exterior Signs of a Chimney Flashing Leak

Homeowners can identify many issues from the ground, often without climbing an extension ladder. Look for conditions that indicate loose flashing, failed seals, or compromised flashing materials.

1. Visible Gaps, Separation, or Loose Flashing

Shadow lines or loose metal indicate failing flashing. If you see gaps between the metal and the chimney, that’s a clear warning sign. Heavy beads of caulk often indicate repeated patch attempts.

2. Damaged, Bent, or Rusted Flashing

Wind-lifted or bent flashing breaks the good seal needed to prevent water intrusion. Rust stains, missing nails, and warped metal mean water is already getting behind the assembly.

3. Shingle Damage Near the Chimney Base

Buckled or loose shingles near the chimney often point to trapped moisture from a flashing leak. Soft decking or granule loss indicates deeper water damage beneath the surface.

4. Water Stains on Chimney Exterior Surfaces

Darkened brick, white mineral residue, or algae growth under the chimney crown or flashing edge suggests ongoing leaks. These are some of the earliest exterior signs of a leaking chimney.

5. Debris Accumulation at the Upslope Side

Without a cricket, leaves, needles, and granules build up around the chimney, slowing drainage. This causes water to pool and force itself sideways into laps and seams.

For additional homeowner-friendly inspection guidance, GAF provides a helpful overview of how properly built crickets improve drainage around chimneys and help prevent chronic leak conditions.

Interior & Attic Signs of a Leaking Chimney

Interior symptoms often appear long before the roof surface looks damaged.

1. Ceiling Stains Near the Chimney Chase

Fresh stains or yellow halos often appear near ceilings where the chimney chase meets living spaces. These stains are common when water infiltration follows framing members into the home.

2. Damp or Moldy Drywall/Walls

Moisture inside the walls behind the chimney suggests water leaking past the flashing. Moldy odors or peeling paint near the fireplace should never be ignored as they indicate long-term moisture exposure.

3. Attic Sheathing Discoloration

During an attic check, look for darkened roof deck, soft OSB, or rusted nails. These all indicate water intrusion from failed flashing or cracks in sealant.

4. Wet or Compressed Insulation

Insulation that appears heavy, compressed, or darker signals active leakage. Wet insulation also increases condensation, worsening the problem.

5. Light Penetration or Drafts Around the Chimney

If daylight shines through small gaps where flashing should be sealed, or if you feel drafts when the weather is calm, the flashing isn’t installed correctly.

When to Call a Professional for a Leaky Chimney

A flashing leak almost never improves on its own. Once water intrusion begins, it spreads through the decking, insulation, and walls.

Call a professional roofing contractor immediately if you notice:

• Active leaks or ceiling stains
• Visible gaps or loose flashing
• Corroded or torn flashing materials
• Soft decking or structural significant damage
• Recurring leaks despite prior sealing attempts

A trained technician can determine whether the chimney needs spot repair, full re-flashing, a cricket installation, or additional sealing. East Mountain Roofing provides free leak inspections, photo documentation, and written estimates across Central & Northern NM.

Schedule a Chimney Leak Inspection in New Mexico

Chimney flashing leaks worsen quickly during monsoon storms and freeze–thaw cycles. If you suspect a roof leak, contact EMR at (505) 264-7081 to inspect, diagnose, and fix the issue before it causes additional water damage.

East Mountain Roofing serves Albuquerque, Santa Fe, Rio Rancho, Cedar Crest, Sandia Park, Edgewood, and surrounding regional communities. Our technicians check flashing, the chimney crown, shingles, masonry, attic clues, and moisture pathways to keep your home safe from long-term damage.