Signs you need this
- Cracks across the concrete crown at the top of the stack
- Brick or mortar pieces in the gutter or on the roof below the chimney
- A damp stain on the ceiling or wall where the chimney passes through
- The stack leans, or the mortar joints above the roof have washed out
- Rusty or tar-patched flashing where the chimney meets the roof
- White staining running down the brick below the crown
The wettest masonry on your building
Everything about a chimney works against it. A wall has a roof over it. A stack has nothing. It takes rain on four elevations, sun on the south face while the north face stays damp, and standing water on top every time it rains. Then the flue runs warm air up the middle of it in winter, so the inside and the outside of the same brick are at different temperatures. That is why a chimney needs attention decades before the walls do.
On older St. Louis houses the stack is often the original soft common brick, laid with lime mortar, and it has been repointed at least once with something harder. Above the roofline you can usually see the history: a band of recent gray portland pointing, a crumbling section above it, and a mortar wash on top that cracked years ago.
Crowns, and why the overhang matters
A proper crown is a cast slab with reinforcement in it. It slopes away from the flue, it overhangs the brick by an inch or so on every side, and it has a drip groove cut into the underside of that overhang. The overhang throws water clear of the brick face, and the drip stops water tracking back underneath and running down the wall. There should also be a bond break where the crown meets the flue tile, because the flue moves with heat and the crown does not.
What we usually find instead is a thin skim of mortar troweled flat across the top of the brick, finished flush with the outer face. It cracks the first winter, water runs straight down the joints below it, and the top eight courses of brick start letting go. Recasting that crown properly is the single highest value repair on most St. Louis chimneys.
Flashing is where the mason and the roofer meet
The other half of a chimney leak is the roof line. Step flashing goes in with the shingle courses, one piece per course, so water running down the roof is carried over the top of each shingle. Counter flashing goes over the step flashing and is let into a cut in the mortar joint, then sealed. Roofing cement smeared into the corner is not flashing. It is a two-year repair, it hides the joint underneath, and it is what we find on most leaking chimneys here.
Permits and historic districts
The City of St. Louis Building Division treats chimney rebuilds as permitted work, and your contractor should pull the permit rather than ask you to. If the building sits in a local historic district, the Cultural Resources Office also reviews exterior work, and the standards can govern the mortar mix, the joint profile and whether a visible stack can be shortened at all. We check the address before quoting so the schedule includes the review time. In University City, Webster Groves and Kirkwood the permit comes from that municipality instead.
How the work runs
- 1
Inspect from the roof rather than the ground
We get on the roof or up a ladder to look at the crown, the top courses, the flashing and the flue opening. Almost nothing that matters on a chimney is visible from the sidewalk.
- 2
Separate the stack from the flashing
Leaks at a chimney come from the masonry or from the roof detail, and often from both. We identify which before quoting, so you are not paying a mason for a roofer's problem.
- 3
Rebuild or repoint to the right level
Where the masonry is sound below the roofline we take the stack down only to solid brick and rebuild from there, salvaging the original brick where it is worth reusing.
- 4
Cast a crown that sheds water
The new crown is cast in reinforced mortar with an overhang past the brick and a drip cut on the underside, with a bond break around the flue so the crown can move independently.
What it typically costs
| Job | Typical range |
|---|---|
| Chimney crown repair Cracked crown cut out and recast with a proper overhang and drip edge | $450 to $1,600 |
| Chimney rebuild above the roofline Stack taken down to the flashing and rebuilt, including new flashing and a cap | $1,800 to $5,500 |
| Repointing an above-roof stack Where the brick is still sound and only the joints have failed | $700 to $2,200 |
| Step and counter flashing, replaced New step flashing woven into the roof with counter flashing let into a cut reglet | $600 to $1,900 |
| Stainless rain cap Keeps rain, birds and squirrels out of an open flue. Sized to the flue itself rather than the stack | $250 to $700 |
| Full rebuild from the basement up Rare. Only where the stack has failed below the roof or has pulled away from the house | $8,000 to $20,000 |
Typical ranges for St. Louis and the surrounding area , reviewed September 2026. Every quote is written and fixed before work starts.