Joints are the chimney’s honesty: brick can look noble for a century while the mortar between quietly gives up. The sequence below runs from cosmetic to structural, walk your own chimney against it, eye-level courses first, then binoculars up the stack.
Stage 1: hairline cracks, watch
Fine cracks along the joint centers or at brick edges, normal shrinkage and thermal cycling, especially on the sun-hammered south face. Not action items alone, but they’re water’s front door, so they earn a spot on the annual watch list.
Stage 2: powdering, plan
The key test: joints that scratch out as sand and dust have lost their binder. Weather-sealing is compromised; erosion accelerates from here (each rain carries a little more away). This is the earliest stage worth repointing, and the cheapest, extent is usually still localized to weather faces and top courses.
Stage 3: recession, schedule now
Joints visibly sunken behind the brick face, quarter-inch, then deeper. Two things are now true: water sits on the exposed brick ledges instead of shedding, and the joint’s effective depth is shrinking toward structural relevance. Prime repointing territory, still routine, won’t stay that way.
Stage 4: missing mortar, this month
Gaps you could park a finger in, wind whistles through them, water pours in during storms, and the bricks above are bridging on their neighbors. Freeze-thaw now works inside the wall. Repointing plus some brick attention is typical at this stage.
Stage 5: loose brick, immediately
The pattern worth knowing
Joints don’t age uniformly: the top three courses and the storm-facing side run two stages ahead of the sheltered faces. So sample where it’s worst, that’s the number that matters. Then let us photograph the full map: free assessment, staged extent, fixed quote for exactly the courses that need work, no more.