The short answer
Yes, a leaning chimney can be dangerous, because a stack that has moved can fall without warning onto the roof, the garden or the street. Keep people and cars away from the ground below it, do not go up to test it, and have it checked promptly. Somerset Building Control lists unstable chimneys among its examples of dangerous structures.
A lean means something has moved, and the cause matters as much as the angle. Treat the stack as unsafe until someone has looked at it.
Why a leaning chimney is a warning
A chimney stack is tall and narrow, with a lot of weight sitting on a small footprint. When it leans, that weight no longer sits over its base, and every gust of wind pushes it a little further. Nothing about the situation improves by waiting, and a stack that looks steady today can shift again in the next gale.
What makes a chimney lean?
Water is the usual start. Worn flashing, the lead tray where stack meets roof, or cracked flaunching, the mortar bed around the pot, lets rain into the brickwork. The mortar softens and the courses slip against one another. Wind then loads the weakened joints, and frost swells any water caught inside them. Sometimes the stack itself is sound and the fault lies below it, in a sagging roof timber or a settling wall. Which of these has happened is what a survey finds out.
A lean that is new is more worrying than one that has looked the same for years, but you cannot judge safety from the ground, so treat both with care. Hairline cracks across the brickwork, bricks that have slipped out of line and gaps opening at the base of the stack all point towards a stack that is still moving.
Keep clear and report it
When Somerset Building Control lists the hazards it deals with as dangerous structures, the unstable chimney is one of them. A stack that threatens a public place is a matter for the council as well as for you, and the number to ring is 0300 303 7790. Give the address, say which way the stack leans and what lies beneath it.
How do you stay safe until it is checked?
Close off the path, drive or garden beneath the stack and keep children, pets and cars out of the fall zone. Do not climb up to push or test it, and never rest a ladder against it. If the stack could land on a pavement, a neighbour's property or a shared access, let the people affected know today. Take pictures from a safe distance, which also helps if you later need to show an insurer what happened.
Then arrange a roofer. Making the area safe comes first, and that can mean taking the top of the stack down to a sound level before the proper repair. If wind brought the lean on, chimney storm damage explains the next steps.
What a roofer checks on a leaning stack
A lean has a cause, and the repair follows the cause.
How is a leaning chimney surveyed?
We begin from a safe position and take pictures from the ground. Once access is set up we go to the stack itself and work along the stack from the pointing to the pot, taking in the flashing and flaunching on the way. We check whether the lean sits in the upper courses only or runs the full height, and we look at the roof timbers and the wall around the base. You see the pictures of your own stack and hear what we found.
Access can be the hard part. A stack above a terraced street may need scaffold on the pavement, which needs a licence from the council that looks after the road, so lead time can matter. Our answer on scaffolding for chimney repairs explains how the licence works, and where the fault is urgent the stack is made safe before any licence arrives.
If cracks run through the bricks as well, the page on a cracked chimney stack covers what they mean.
Repair or rebuild
Pointing will not straighten a stack that has moved. Once bricks have shifted off line, new mortar only locks them in at the wrong angle.
Does a leaning chimney always need rebuilding?
Usually the leaning part comes down and goes back up plumb. We rebuild from the point where the stack is still sound, often the roofline, using bricks that match the original, then fit new flashing, flaunching and the pot. Where the fault sits below the roofline, a mason or a structural view may be needed first, and we tell you so before any price is agreed.
The price depends on the stack's height, the scaffold, how many bricks must be matched and whatever the survey turns up beneath the stack, such as damp timbers or a loose wall head. The written price that follows our survey is one total, so you see the whole job before it begins. Begin at the chimney repairs overview, and when you are ready, ring us on 01823 297042 with the stack in sight of a window or the road.
More on unstable stacks
Can a leaning chimney be pushed straight again?
No. A stack that has leaned has moved at its joints, and pushing or repointing will not restore it. The usual cure is to take the leaning part down and rebuild it plumb, in matched brick where it matters, with new flashing and flaunching. The survey shows whether the fault lies in the stack or in what it sits on.
Who pays to make a dangerous chimney safe?
The owner does. Somerset Building Control puts the bill on whoever owns a building when it turns dangerous, covering everything needed to secure it, which is why an early survey is cheaper than waiting for a collapse. If a storm damaged the stack, tell your insurer before you order any repair.
The full picture: Chimney repairs in Taunton ยท More short answers