Chimney Flashing: Allentown’s #1 Winter Roof Leak (How to Fix It Right)

If you’ve ever seen a brown ceiling stain near a fireplace wall—or smelled musty odors after a storm—there’s a good chance the culprit is chimney flashing. With Allentown’s older brick chimneys and freeze–thaw winters, this is the most common leak we’re called to fix. Here’s how to spot it, stop it, and prevent it from coming back.

Why chimneys leak so often here

• Aging mortar + brick: Freeze–thaw cycles open tiny gaps that let wind-driven rain in.

• Improper “repairs”: Tar blobs and caulk over old metal don’t last.

• Missing counter-flashing: Step flashing alone isn’t enough on brick.

• No cricket on wide chimneys: Water piles up behind the chimney and finds a way inside.

Fast symptoms checklist (do you have a chimney leak?)

• Stains on ceilings/walls adjacent to the chimney (often triangular or vertical).

• Damp, crumbly plaster near the fireplace wall.

• Soft decking or spongy feel along the chimney line (found during inspection).

• Shingles around the chimney that look patched, tarred, or mismatched.

• Efflorescence (white mineral trails) on chimney bricks or cap.

If two or more sound familiar, it’s time for a proper flashing reset—not another band-aid.

The correct flashing assembly (what “good” looks like)

A long-lasting chimney detail has four parts:

1. Step flashing (under each shingle course) where roof meets chimney sides.

2. Counter-flashing (cut into mortar joints) overlapping the step flashing—this is what keeps water out of the wall.

3. Back pan + cricket behind the chimney on the uphill side to split and shed water.

4. Front pan at the downhill side, lapping onto shingles.

Add ice & water shield beneath all these metal transitions and you’ve got a winter-ready assembly for the Lehigh Valley.

Red flag: If you see metal glued to brick with sealant but not cut into mortar joints, that’s not true counter-flashing—expect a revisit.

Repair vs. full reset (choose the right fix)

Spot repair (works when…)

• Flashing metal is structurally sound.

• Mortar joints are intact with minor gaps.

• Leak is recent and localized.

What we do: Clean and prep; replace compromised step pieces; re-bed small gaps; re-seal transitions with roofing-grade sealants; add targeted ice & water.Goal: Buy time on otherwise solid systems.

Full flashing reset (best for long-term)

• Recurrent leaks or prior tar patches everywhere.

• Deteriorated mortar or loose/corroded metal.

• No cricket behind a wide chimney (≥30") or a steep, high-flow slope.

What we do: Tear back shingles; install ice & water; new step flashing each course; new back/front pans; fabricate/install a proper cricket; grind mortar joints and install true counter-flashing; weave new shingles; photo document the whole assembly.

Bonus: Don’t forget the top

A leaky chimney crown/cap, cracked flue liner, or missing cap will invite water straight down the stack. During a roof visit we’ll check:

• Crown cracks and wash

• Flue cap condition

• Brick/mortar health (repointing needs)

Roof-level flashing is only half the battle—fixing the top keeps everything dry.

What it should (and shouldn’t) look like from the ground

Good signs: Clean step lines, neat metal transitions, counter-flashing visible and tucked into mortar joints, no tar globs.

Bad signs: Thick black sealant smeared up the brick, lifted shingles at the sidewalls, rusty or pieced-together metal, sagging debris pile behind the chimney (no cricket).

Snap a few photos with your phone from the yard; we can usually tell quickly whether you need a reset.

When to combine chimney work with a re-roof

If your shingles are aging (≈20–25 years) or you’re already planning a replacement, it’s best to reset flashing during the re-roof. You’ll:

• Avoid double labor

• Get fresh ice & water underlayment and proper ventilation

• Match metals and shingles for a clean, warrantable system

For standard asphalt tear-off & replacement, our typical range is $675–$875 per square (materials-dependent and scope-based). Chimney resets and crickets are priced as add-ons after inspection.

FAQs

Will caulk fix my chimney leak? Briefly, maybe—but it’s a temporary patch. Without true counter-flashing and a cricket where needed, water will find a path again.

Do all chimneys need a cricket? Not all. Wider chimneys (≈30"+) or high-flow roof areas should have one to split water.

Can you fix flashing in winter? Yes, with the right materials and a dry window—but fall is ideal for permanent resets.

The bottom line

In Allentown, chimney flashing is the #1 winter leak source—because it’s detailed work that shortcuts can’t solve. Get the assembly right (step + counter-flashing, pans, cricket, and ice & water) and you’ll be dry for years.

Seeing stains or suspect flashing? Call 610-587-2709 for a same-week chimney and roof inspection in Allentown, Whitehall, Emmaus, Macungie, and nearby. We’ll document the issue with photos and give you clear repair vs. reset options.

P.S. Keep water flowing away from your roof and masonry: we also offer gutter cleaning and soft/pressure washing as recommended maintenance.