Professional Chimney Flashing Installation and Repair

You know that thin metal strip where your chimney meets the roof? That’s flashing, and it’s probably the most underappreciated part of your entire chimney system. Until it fails, anyway.

Here’s what most Kansas City homeowners don’t realize: chimney flashing is responsible for more water damage claims than just about any other roofing component. When it’s installed correctly, you’ll never think about it. When it’s not, you’re looking at water stains on your ceiling, rotted roof decking, and repair bills that make you wince.

What Chimney Flashing Actually Does

Flashing creates a waterproof seal between your chimney and roof. Think of it as a custom-fitted gasket that keeps rain, snow, and ice melt from sneaking into your home. It’s not just one piece either. A proper flashing system has multiple components working together: base flashing, step flashing, and counter flashing (sometimes called cap flashing).

The base flashing sits at the bottom of your chimney where water naturally flows downward. Step flashing runs up the sides, with individual pieces layered under each shingle course like fish scales. Counter flashing gets embedded into the chimney mortar joints and covers the step flashing from above.

It’s a system. And like any system, one weak link compromises everything else.

Why Flashing Fails in Kansas City

Our weather is brutal on chimney flashing. We get temperature swings that’d make your head spin—70 degrees one day, 20 degrees the next. That constant expansion and contraction works flashing loose over time, especially if it wasn’t installed with enough flexibility built in.

Then there’s our freeze-thaw cycles. Water gets behind marginally-installed flashing, freezes, expands, and pushes things apart even more. Do that 30 or 40 times a winter and you’ve got problems. Add in our humid summers where moisture condenses in all the wrong places, and Kansas City chimneys take a real beating.

I’ve seen flashing fail in as little as five years when it’s done wrong. Done right? It should last 30 years or more.

Signs Your Flashing Needs Attention

Water stains on the ceiling near your chimney are the obvious red flag. But by the time you’re seeing stains, water’s been getting in for a while.

Look for rust spots or corrosion on the flashing itself. Check if the metal looks pulled away from the chimney or roof. Sometimes you’ll see gaps where the counter flashing meets the bricks—that’s often because the mortar joints have deteriorated and the flashing is just hanging there doing nothing.

After heavy rains, grab a flashlight and check your attic. Look at the roof decking around the chimney. Dark stains, soft spots, or that musty smell all mean water’s getting past your flashing. Don’t wait on this stuff. Water damage spreads fast, and what starts as a $800 flashing repair can turn into a $5,000 roof deck replacement if you ignore it long enough.

The Right Way to Install Chimney Flashing

Here’s the thing about flashing installation: it’s part roofing, part masonry, and part sheet metal fabrication. That’s why so many roofers and chimney companies get it wrong—they’re only expert in one of those three areas.

Proper installation starts with removing old flashing completely. You can’t just slap new stuff over old and hope for the best. The roof shingles around the chimney usually need to come up too, because step flashing has to be woven in with the shingle courses. Anyone who tells you they can do it without touching your shingles is cutting corners.

The base flashing goes down first, sealed to both the chimney and roof with high-quality polyurethane or silicone sealant. Not tar. Not roofing cement. Those crack and fail. Then comes the step flashing, installed one piece at a time as each row of shingles goes back down. Each piece should overlap the one below it by at least three inches.

Counter flashing gets cut into the mortar joints—actually cut in, not just stuck on with caulk like I see all the time. The slots should be about an inch deep, and the flashing gets bent and inserted, then the joints get repointed with fresh mortar. This part requires real masonry skills, not just roofing know-how.

Material Choices Matter More Than You’d Think

Most flashing around here is aluminum, copper, or galvanized steel. Aluminum is affordable and doesn’t rust, but it’s soft and can tear or dent easily. Copper costs more—sometimes three times as much—but it’ll outlast your roof and develop that distinctive green patina over time.

Galvanized steel sits in the middle on cost, but it can rust if the zinc coating gets scratched during installation. I’ve seen it happen more than once when someone’s banging pieces into place without care.

For Kansas City’s climate, I lean toward copper or heavy-gauge aluminum. The investment pays off when you’re not dealing with repairs every ten years. And if you’ve got a brick chimney with copper flashing, that green patina actually looks pretty sharp against red brick.

Repair vs. Replacement: Making the Call

Sometimes you can get away with repairs. A small gap in the counter flashing? That can be resealed and repointed without tearing everything out. A couple of loose pieces of step flashing on one side? Yeah, those can be secured and reflashed locally.

But if your flashing is 20+ years old and showing multiple failure points, replacement makes more sense than piecing it together. You’re just kicking the can down the road otherwise, and you’ll end up paying twice—once for the repairs and again in a couple years for the full replacement you should’ve done the first time.

Trust me on this one: I’ve had customers try the “patch it one more time” approach, and it rarely works out cheaper in the long run.

What Professional Installation Should Cost

In the Kansas City area, expect to pay somewhere between $800 and $2,000 for complete flashing replacement on a standard-sized chimney. That’s for aluminum flashing with proper removal of old materials and correct installation of all components.

Copper bumps that up to $1,500 to $3,500 depending on chimney size. Larger chimneys or ones with multiple angles obviously cost more because there’s more material and labor involved.

If you’re also doing roof work at the same time, the flashing cost usually comes down a bit since the roofer’s already there and shingles are already being disturbed. That’s actually the ideal time to address flashing—when you’re getting a new roof anyway.

Repairs run $300 to $800 typically, but that depends entirely on what needs fixing and how accessible everything is.

Getting It Done Right

Look, chimney flashing isn’t glamorous. Nobody ever brags about their perfectly installed step flashing at a barbecue. But it’s one of those things that protects your biggest investment—your home—from serious water damage.

If you’re in the Kansas City area and you’re seeing warning signs, don’t mess around with quick fixes or the cheapest bid you can find. This is skilled work that requires real expertise in multiple trades. Done right the first time, you won’t have to think about it again for decades.

We handle chimney flashing installation and repair throughout the Kansas City metro. If you want someone to take a look at what you’ve got going on up there, give us a call. No pressure, just honest assessment and straightforward pricing.