A leaning chimney is a heavy structure losing its footing.

Leaning Chimneys: diagnosed and explained.

A chimney is one of the heaviest, most concentrated loads on your property, and it usually stands on its own footing, separate from the house foundation. That makes it an early warning system: when soil conditions change, the chimney often moves first. From the yard you might see the stack tilting away from the house, a widening gap between the chimney and the siding, or flashing at the roofline that has pulled apart. Inside, you might find cracks in the wall the chimney backs up to. The mechanism is simple physics. The chimney footing sinks or rotates as the soil beneath it compresses, erodes, or cycles through clay shrink and swell, and because the chimney is tall and rigid, even a small footing rotation becomes a visible lean at the top. This is not a problem that stabilizes on its own. The lean shifts the center of gravity, which loads the low side of the footing harder, which accelerates the settlement. A separating chimney also opens paths for water and pests, and in earthquake country an unstable masonry stack is a real safety concern, which is why a measured evaluation belongs near the top of the list.

For the repair side of this, the foundation repair solutions page lists every method Dalinghaus installs, including the ones that fix problems other than leaning chimneys.