Chimney Flashing Repair in the Denver Metro

Hail replaces roofs in Denver by the neighborhood. The May 8, 2017 storm alone led to about 100,600 homeowners' insurance claims, according to the National Insurance Crime Bureau figures reported by FOX Weather. A new roof is the moment when chimney flashing is most often reused, bent back into place or smeared with tar instead of replaced. The shingles are the roofer's job; the counter flashing set into the brick joints is masonry work, and it falls between trades.

Snow is the other cause. Denver averages 49 inches a year and Boulder 92.8, by NOAA's normals, and snow drifts against the uphill side of a chimney, melts in the sun and refreezes at night. That water backs up under weak or badly lapped flashing and finds its way into the attic. Expect $300 to $600 to reseal metal that is still sound, or $800 to $1,800 for new step and counter flashing.

Signs you need this

• A ceiling or wall stain right beside the chimney
• Drips in the attic after snowmelt, not just rain
• Caulk or roofing tar smeared along the chimney base
• Flashing bent, lifted or pulled out of the joints
• A leak that started after the roof was replaced

How we do it

1. Find the leakThe leak check is free. We look from the attic and the roof, and test with water if we need to prove the source.
2. Remove the old workTar, caulk and failed metal come off so we can see the roof deck and brick underneath.
3. Step and counter flashingStep flashing weaves under each shingle course; counter flashing is cut into the mortar joints and folded over it.
4. Add a cricket if neededOn a wide chimney, a small peaked saddle on the uphill side steers snowmelt around it. That is priced at the inspection.

My roof was just replaced. Why is the chimney leaking now?

Usually because the old flashing was reused, or new step flashing went in without proper counter flashing over it, or the gap was filled with sealant that cracked after one winter. Sealant alone can look fine on install day and fail by spring.

We photograph what we find, which helps if you need to go back to the roofer. If the counter flashing was never cut into the brick, we do that part properly so the roof and the chimney finally meet.

Why does it leak only in spring or after snow?

Melting snow behaves differently from rain. It sits against the chimney for days, feeding a slow trickle under the flashing, and an ice ridge can hold that water in place. A chimney that never leaks in a summer storm can leak every March.

On a wide chimney, a cricket on the uphill side helps a lot, because it stops snow from piling against the brick and sends the melt around it.

Is caulk ever enough?

When the metal is sound and correctly installed, and only the sealant at the top edge has dried out, resealing is a fair fix at $300 to $600. When the metal is bent, rusted, too short or not cut into the joints, caulk only hides the problem, and new flashing at $800 to $1,800 is the repair that lasts.