Understanding Chimney Flashing and Roof Leaks

When a Malta homeowner finds water stains on the ceiling near the chimney, flashing is usually the first suspect. It’s the part of the system most responsible for keeping rain out where the chimney meets the roof.

What Flashing Is

Flashing is the layered metal seal where the chimney passes through the roofline. It’s typically made of two parts: step flashing woven into the shingles, and counter flashing set into the chimney’s mortar joints that laps over the step flashing. Together they form a weatherproof joint that lets the roof and chimney move independently while shedding water away from the opening. Homeowners across Malta count on timely attention to keep their systems safe.

How It Fails

Flashing fails in a few predictable ways. The metal corrodes or lifts, the caulk or tar someone used as a shortcut dries and cracks, or the counter flashing pulls out of deteriorating mortar joints. Any of these lets water run down behind the flashing and into the roof deck, framing, and ceiling below, often appearing as a stain some distance from the actual leak. Our chimney repair service covers exactly this kind of work.

Why It’s Misdiagnosed

A chimney leak doesn’t always show up as a wet chimney. Water travels along rafters and sheathing before it drips, so the stain can be feet away from the flashing. Homeowners sometimes replace shingles or chase phantom roof problems when the real culprit is a quarter-inch gap at the chimney. A proper inspection traces the water back to its entry point.

The Right Repair

Good flashing repair means proper metalwork, not a bucket of roofing tar. We cut fresh reglets into the mortar where needed, install correctly lapped counter flashing, and seal it to last. Paired with a sound crown and cap, well-done flashing keeps the whole chimney-to-roof junction dry through years of Illinois weather.

Don’t Reach for the Caulk

When a chimney leaks, the tempting quick fix is a tube of caulk or a bucket of roofing tar smeared along the seam. It might buy a few dry weeks, but these materials dry out, crack, and trap water behind them, often making the next repair harder. Proper flashing is metal, cut and lapped to shed water by design, not sealed shut with goo. If a previous owner or handyman tarred over the flashing, it’s usually a sign the real joint has been failing for a while and needs doing right.

Published November 4, 2026 · Imperial Chimney Sweepers, DeKalb, IL