Maintenance & Repairs

Chimney Flashing Repair: What You Need to Know

Updated October 2026 · 4 min read · By the Knoxville Roofing Quotes team

If your roof leaks near the chimney, the flashing is the most likely culprit. It's one of the most common roof repairs, and one of the most commonly botched. Here's how chimney flashing works, why it fails, and how to tell a real fix from a tube of caulk.

What Is Chimney Flashing?

Flashing is the weatherproofing system where your chimney meets your roof. It's made up of several pieces of metal that work together to direct water away from this vulnerable intersection.

A proper chimney flashing system includes:

Step flashing: L-shaped pieces woven into the shingles along the sides
Counter flashing: Metal set into the chimney's mortar joints that overlaps the step flashing
Base (apron) flashing: At the bottom, where the chimney meets the roof on the downhill side
Saddle/cricket: A small peaked ridge behind the chimney that diverts water around it

Why It Fails

Age and Weather

Metal expands and contracts with temperature changes, and sealants dry out. Knoxville sees around 68 nights a year at or below freezing, according to the National Weather Service, so the joint between masonry and roof goes through a lot of freeze-thaw cycles. Over time, sealant cracks and pieces work loose.

Poor Initial Installation

A lot of flashing problems trace back to the original installation: caulk used instead of proper counter flashing, step flashing skipped, or no cricket behind a wide chimney.

Chimney Movement

Chimneys can settle, pull slightly away from the house, or develop cracks. That movement breaks seals and opens gaps.

Roof Replacement Without Reflashing

When roofs get replaced, some contractors reuse old flashing to save time. Old, worn flashing on a new roof can become the weak point. Ask every roofer who quotes your job whether they'll install new flashing, and get the answer in writing.

Signs Your Flashing Is Failing

Water stains on the ceiling or in the attic near the chimney
Visible rust on the flashing
Cracked or missing caulk or sealant
Flashing pulling away from the chimney
Gaps where flashing meets the masonry
Missing pieces
Debris piling up behind the chimney

A stain near the chimney isn't always the flashing. Cracked masonry, a damaged chimney crown or a missing cap can let water in too. Our guide on when to repair a leaking roof covers how to track down the source.

Repair vs. Replace

Repairs such as resealing, refastening loose pieces or replacing a few damaged sections can work when the rest of the flashing is sound. HomeAdvisor's national cost data (updated June 2026) puts flashing repairs at roughly $200 to $500. A chimney that needs new counter flashing, a cricket or masonry work will cost more, so get a written quote.

Full replacement makes more sense when the flashing is rusted through, has been patched repeatedly, or is original to an older roof. If you're replacing the roof anyway, that's the right time to replace the chimney flashing too.

The Cricket Question

The International Residential Code, the model code Knox County builds on, calls for a cricket on the uphill side of a chimney that's more than 30 inches wide, measured parallel to the ridge. Many older homes don't have one.

Without a cricket, water and debris pile up behind a wide chimney, which speeds up wear and makes leaks more likely. If you're having flashing work done on a wide chimney that lacks a cricket, ask the roofer whether one should be added and include it in the quote.

Why Caulk Alone Doesn't Work

Watch for this: some contractors smear caulk over the flashing and call it fixed. Caulk breaks down with sun exposure and cracks as temperatures swing. It's a temporary patch, not a repair.

Proper flashing repair involves:

Removing old sealant and failed pieces
Replacing damaged flashing
Making sure each piece overlaps the next so water runs down and out
Setting counter flashing into the mortar joints
Using sealant in addition to, not instead of, the metal flashing

Who Should Do the Work?

Flashing repair sits between two trades. Here's how to think about it:

Call a roofer if:

The flashing itself is the problem
You need a cricket installed
It's part of a roof replacement

Call a mason if:

The chimney masonry is cracked or damaged
The mortar joints where the counter flashing sits are failing
The chimney needs tuckpointing or crown repair

Often the answer is both: a mason repairs the chimney, then a roofer installs the flashing. Coordinate the two, or find a company that handles both. Our roof leak repair page explains what to expect from a leak call.

Leak Near the Chimney?

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Prevention

Look at the chimney from the ground once or twice a year for gaps, rust or loose pieces. Binoculars help; there's no need to climb up.
Keep debris from piling up behind the chimney
Fix chimney masonry problems promptly
When you replace your roof, ask for new flashing rather than reusing the old

Our roof inspection checklist covers what else to look at while you're checking the chimney.