Roof Leaks Around Chimneys: The Most Common Source of Attic Water Damage

In our experience inspecting roofs throughout North Jersey, the chimney is the source of more water intrusion complaints than any other single point on a roof. The reason is straightforward: the chimney penetrates the roof deck, creating a joint that must be waterproofed — and that waterproofing has multiple components that each fail differently over time.

The Flashing System Explained

A properly detailed chimney-to-roof junction uses three layers of flashing:

Step flashing: Individual L-shaped pieces of metal woven into the shingles along the sides of the chimney. Each piece overlaps the one below. Step flashing is installed during the roofing process — it can't be properly installed after shingles are down without disturbing them.

Counter flashing: A separate layer of metal embedded in the chimney mortar joints and bent down over the step flashing. The counter flashing is the weather barrier; the step flashing is the backup. The two layers work together to create a positive drainage joint.

Chimney cricket or saddle: On chimneys wider than 30 inches, a peaked metal structure is installed behind the chimney (on the upslope side) to divert water around rather than allowing it to dam up and pool against the chimney. A missing cricket is one of the most common causes of chronic chimney-side leaks.

How Flashing Fails

Counter flashing dislodgment: As the chimney settles independently from the house, the mortar joint where counter flashing is embedded can crack and release. The flashing then lifts out, leaving the step flashing exposed.

Caulk-only flashing: Many older installations — and some poor-quality newer ones — use roofing cement or caulk instead of properly embedded metal counter flashing. Caulk fails within 5–7 years; embedded metal lasts 20–30.

Corrosion: Galvanized steel flashing eventually corrodes. Copper doesn't — it's the premium material for chimney flashings.

Missing cricket: Water dams against the back of wide chimneys and infiltrates at the back joint.

What Proper Repair Looks Like

A proper chimney flashing repair involves:

1. Remove all existing caulk and compromised flashing
2. Install new step flashing woven with shingles (requires lifting existing courses)
3. Embed new counter flashing in cut mortar joints with expansion anchors and sealant
4. Install chimney cricket if absent on chimneys over 30" wide
5. Apply roofing cement only as a supplemental sealer, never as the primary barrier

A flashing patch that consists only of applying roofing cement over existing failed material is a temporary fix — it typically lasts one to three years before the underlying problem reasserts itself.

Troy & Henry LLC handles chimney flashing repair and installation throughout North Jersey. Call 1-800-886-2077 for a free inspection.