Next-day appointments
Call or book today and we'll do our best to get a pro to you tomorrow.
Do not light another fire until this has been looked at.
The short answer
Masonry does not lean back. Whatever moved it is still moving it.
A leaning chimney has moved, and masonry that has moved does not move back. The cause is almost always below what you can see: a footing that has settled, soil that shifts with the seasons, or a stack that was tied into the house badly and has pulled away as the mortar failed. What makes this different from every other problem on this site is that it is a falling hazard as well as a repair. A stack separating from the wall can come down in a storm, and it will not give much warning when it does.
Sight it against something straight

A downpipe, a corner board or a plumb line on a string. A gap that widens up the stack is the measurement that matters.
Before we get there
None of this fixes it. All of it stops the problem getting more expensive between now and the visit.
Keep people and cars out from under it, and off the roof around it, until someone has looked.
Measure the gap between the stack and the wall at the bottom and at the top. The difference is the lean.
Mark the gap with a pencil line and a date. Movement over weeks is a different conversation from movement over decades.
Do not use the fireplace. A stack that has moved has almost certainly broken the liner inside it.
Photograph all four faces. A mason needs to see which way it is going and whether the joints are opening on one side.
Work out which is yours
Ordered by how often it turns out to be the answer, so you can stop reading once you recognise yours.

A chimney is enormously heavy and older ones were often built on a footing that would not pass today. Once it settles unevenly the whole stack tilts, and nothing above ground fixes that.

Clay soils swell when wet and shrink when dry, so a stack can move measurably between seasons. Drainage against the foundation is often part of the answer.

An exterior chimney is tied into the framing. When those connections corrode or the mortar around them fails, the top starts pulling away while the base stays put.

Joints that have washed out let courses shift relative to each other. The lean develops gradually and shows first as a stepped crack up one face.

Rarely the whole cause and usually the accelerator. Saturated masonry loses strength every freeze, and a stack already marginal gets there faster.
What actually fixes it
Fall Special
Call or book today and we'll do our best to get a pro to you tomorrow.
Anything that needs attention is shown to you and explained in plain words.
If something needs fixing, you get the price in writing first. Saying no costs nothing.
Good to know

Founded by Ryan Carter in 2019. Every page you read here is reviewed by Ethan Miller, our chimney specialist. A written estimate before any work, and the findings in writing whether or not anything needs doing.
More about who we are →