Why Is My Roof Leaking Around the Chimney?
A chimney leak doesn’t always mean the chimney is the problem. More often, it’s the flashing—the metal waterproofing where the roof meets the chimney.
Unfortunately, chimney flashing is one of the most overlooked details during a roof replacement. Many roofing contractors either reuse old flashing or install an outdated one-piece flashing system that is far more likely to leak over time.
If you’ve noticed water stains near your fireplace, ceiling discoloration, or leaks during heavy rain, your chimney flashing deserves a closer look.
Watch: Why Chimneys Leak After a Roof Replacement
Jay explains why chimney flashing is one of the biggest shortcuts taken during roof replacement.
The #1 Cause of Chimney Roof Leaks
Your roof and your masonry chimney are two completely different materials.
- Your roof expands and contracts every day.
- Your brick chimney barely moves at all.
When the two are rigidly connected with a single piece of metal, something eventually gives.
That’s why properly installed chimney flashing should be a two-part system.
One-Piece Flashing vs. Two-Piece Flashing
Many roofers install this:
One-Part Flashing
- Roof flashing and counter flashing formed as one piece
- Attached directly to the chimney
- Roof movement stresses the metal
- Caulk becomes the primary waterproofing
- More likely to leak over time
We recommend this:
Two-Part Chimney Flashing
- Step flashing is installed with the shingles.
- Separate counter flashing is installed into the chimney mortar joints.
- Each component moves independently.
- Accommodates normal thermal expansion and contraction.
- Water is shed by the metal—not by caulk.
Think of it like an expansion joint on a bridge. The movement is expected, so the flashing system should be designed to allow it.
The Hidden Shortcut During Roof Replacement
Here’s something many homeowners never realize.
Most roofing contracts include wording like:
“Replace flashing as needed.”
That sounds reasonable…
Until you realize what it often means.
Instead of installing new flashing, the contractor simply reuses the existing flashing around the chimney, roof protrusions and roof/wall joints.
The shingles may be brand new, but the waterproofing protecting some of your roof’s most vulnerable areas could already be 20 years old.
Why Reusing Chimney Flashing Is Risky
Old flashing may:
- Have corrosion beginning underneath
- Be bent and damaged with holes from the previous roof’s fasteners
- Be loose
- Have failed sealants
- Have hidden dammage
- Be improperly installed from the previous roof
Once new shingles are installed around old flashing, correcting the problem later often requires removing portions of the new roof.
Replacing the flashing during the roof installation is usually far less expensive than repairing a leak afterward.
At Blue Fox Roofing, We Believe Chimney Flashing Should Be Replaced
When we replace a roof, we believe chimney flashing deserves the same attention as every other roofing component.
Rather than relying on old materials, we recommend installing:
- New step flashing
- New counter flashing
- Flashing that’s fully integrated with the new roofing system
- Mechanical waterproofing instead of depending primarily on caulk
It’s a detail many homeowners never see—but it’s one that can prevent years of frustrating leaks.
Questions to Ask Before Signing a Roofing Contract
Before selecting a roofing contractor, ask:
- Are you replacing the chimney flashing or reusing it?
- Is the flashing a one-piece or two-piece system?
- Does your proposal specifically include new counter flashing?
- If it says “replace as needed,” what exactly does that mean?
If the salesperson can’t answer these questions clearly, that’s worth paying attention to.
Don’t Wait Until Water Shows Up Inside
A chimney leak often starts small.
By the time water reaches your ceiling, insulation, framing, drywall, and even the chimney chase may already have been affected.
If you’re replacing your roof—or already noticing leaks around your chimney—we’re happy to inspect the flashing and explain exactly what we find.
Schedule your roof inspection today and we’ll show you what’s protecting your chimney—and what isn’t.
