By Daniel Watkins, Noble Chimney Sweepers.
Stand at the base of your chimney and look up with binoculars. If the mortar between the bricks has receded, gone sandy, or dropped out in chunks, you are looking at failed joints — and September is the last comfortable month to deal with them before freeze-thaw season takes another run at the stack. Here is how to judge whether joints need repointing, and what separates a real repair from a cosmetic smear.
What tuckpointing actually is
Tuckpointing means cutting the deteriorated mortar out of the joints to a proper depth and packing fresh mortar back in. The key word is cutting. Mortar smeared over the face of a bad joint has nothing to bond to and pops off within a season or two, which is why some chimneys look repaired for a year and then look worse than before.
Joints are the sacrificial part of a masonry chimney by design. Mortar is meant to be softer than brick so that movement and moisture destroy the joint rather than the brick face. That means degraded joints are normal on an older stack — but they are also the doorway water uses to get inside.
Why the joints go first up top
A chimney is the one masonry element exposed on all four sides, above the roofline, with no heated interior behind it. It soaks rain, dries in wind, and swings through freeze-thaw cycles far more often than the walls of the house. Every cycle where water sits in a joint and then freezes widens the gap slightly. Repeat that a few hundred times over a Chicago-area winter and the joint is gone.
How to tell if yours needs it
Scratch a joint with a key or a screwdriver tip. Sound mortar resists; failed mortar crumbles into sand and gives up a quarter inch without effort. Other tells: gaps you can see daylight through, mortar dust collecting on the roof or in the gutter below the chimney, joints that have receded noticeably deeper than the brick face, and brick that has started shifting or leaning.
Water stains on the ceiling near the chimney chase, or a damp smell inside the firebox after rain, often trace back to open joints rather than to the flashing. We check both, because the fix is completely different depending on which one is letting water in — that is part of what a chimney inspection is for.
Repoint now or rebuild later
Repointing is the cheap moment in a chimney’s life. Once water has been running through open joints long enough, it saturates the brick, and the next freeze cycle spalls the faces off. Spalled brick cannot be repointed — it has to be replaced, which usually means taking the stack down to sound courses and rebuilding. The gap in cost and disruption between those two jobs is enormous, and the only thing separating them is time.
Getting it right in Lockport’s older housing stock
Much of Lockport has masonry old enough that the original mortar was soft lime-based material rather than modern portland mix. Packing a hard, high-portland mortar into a soft historic joint is a genuine mistake: the new joint becomes stronger than the brick around it, and the brick starts taking the damage instead. Matching the existing mortar’s strength and profile matters as much as doing the work neatly.
Repointing pairs naturally with the rest of the waterproofing picture — the crown, the cap, and the flashing all have to do their jobs or the joints just fail again. Our chimney repair page walks through how those pieces fit together, and the pricing page lists what work costs.
Timing the work
Mortar needs above-freezing temperatures to cure properly, which in this area realistically closes the window sometime in November and does not reopen until spring. Booking now means the joints are sealed before the first hard freeze rather than after it has already done another winter of damage.
Noble Chimney Sweepers is owner-operated, certified, bonded and insured. I have spent 14 years on chimneys in this area, and you get the price up front before any work starts. Call (708) 432-5747 — we answer seven days a week, 7 AM to 7 PM.
Frequently asked questions
How deep does the old mortar have to be cut out?
The standard rule of thumb is roughly two and a half times the joint width, so that the new mortar has enough depth to bond and lock in. Surface skimming over failed joints does not qualify as repointing.
Can I just seal the chimney instead of repointing it?
No. A breathable water repellent is a good final step over sound masonry, but sealing over open joints traps moisture already inside the brick and accelerates spalling. Repair first, treat second.
How long does repointed mortar last?
Properly cut and packed joints with a matched mortar typically last decades. Joints that were smeared rather than cut often fail within a couple of winters, which is the usual reason a chimney gets “repointed” twice in five years.
Does the whole chimney need repointing or just part of it?
Usually just the exposed sections above the roofline, since that is where the weathering happens. Spot repointing sound lower courses accomplishes little.
Can tuckpointing be done in cold weather?
Mortar cures poorly near freezing and can be damaged by a hard frost before it sets. In this climate the practical season runs from spring through late fall.
Will repointing stop my ceiling leak?
Only if the joints are where the water is entering. Flashing, a cracked crown, and a missing cap are equally common sources, so the entry point should be identified before anyone starts mixing mortar.
Why does the new mortar look a different color?
Fresh mortar cures lighter and darkens over the first year, and decades of weathering have changed the color of the old joints. A close match at installation will usually blend as it ages, though an exact match to weathered mortar is not realistic.
Is repointing something a homeowner can do?
Ground-level practice on a garden wall, maybe. On a chimney it involves roof work at height, grinder use in tight joints, and matching mortar strength to old masonry — three ways to make the problem worse. Basic maintenance you can handle safely is covered on our DIY page.
Published September 14, 2026