Why does my chimney look like it is leaning to one side?
A chimney that looks like it leans has usually lost structure. The mortar joints have failed, the brick has shifted, or the base underneath has moved. A leaning stack is a structural problem, not a cosmetic one, so keep people and pets away from its base and do not light the fireplace until a technician has looked at it.
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Sometimes the lean is partly an illusion. A steep roof, a camera angle or a chimney that was never built perfectly plumb can all fool the eye. A lean that is new, or one that comes with cracks, gaps or loose brick, is the kind to take seriously.
Why a chimney leans
The most common cause is water. A cracked crown, open mortar joints or failed flashing let water into the masonry. Over time the mortar softens and crumbles and the brick starts to spall, which means the faces flake off. Once the joints can no longer hold the courses in line, the stack above the roof can begin to tilt.
The other cause is movement below. A chimney is heavy, and if the ground or footing under it settles, the whole stack can pull away from the house. A gap that opens between the chimney and the wall is a typical sign of this. The repair there is different, because the cause underneath has to be dealt with before the masonry above is rebuilt.
Where the lean sits matters. If only the top section above the roofline is out of line, that section may need to be taken down and rebuilt. If the whole chimney leans from the base, a mason will want to find out why before deciding what to repair.
What you can check yourself
Compare it to a straight line
Stand well back and look at the chimney beside a door frame, a house corner or a downspout. Check from more than one side so you can tell a real lean from an angle that misleads.
Look for a gap at the wall
From the ground, see whether daylight or a dark line shows between the chimney and the house. A gap that looks wider than before is worth photographing.
Look at the ground below
Brick pieces, chunks of mortar or flakes of crown in the yard or on lower roofs mean the masonry is breaking down. Keep clear of that area and do not collect the pieces from the roof.
Check inside near the chimney
Look for new cracks in the wall or ceiling beside the chimney breast, or gaps around the firebox opening. Do not light the fireplace while you wait for a visit.
Take dated photos
A few photos from the same spot, taken a week or two apart, show whether the lean is changing. The technician can use them.
When to call a technician
Call as soon as you see a lean you can measure by eye, a gap at the house wall, brick coming loose or cracks that are getting wider. None of these is something to look at again next season. A leaning stack may also have a damaged liner behind the brick, so do not use the fireplace. If anyone has a headache or dizziness while a fire has been burning, get outside and call 911.
One Call Chimney is a referral and scheduling service. One call to (866) 576-7943 arranges an independent chimney technician or mason to inspect the chimney. The estimate is free, the technician gives the price before any work starts, and you approve it first. Rebuilding a stack can fall under local permit rules, which vary by city and county, so check with your local building department.
What the technician will do
- Inspect the whole stackThe technician looks at the crown, joints, brick faces, flashing and the base to find out whether the lean comes from water damage or from movement below.
- Repair or recast the crownA cracked crown is repaired or recast with an overhang and a drip edge, so water runs clear of the brick instead of into it.
- Repoint and replace brickFailed joints are repointed to match the existing work, and spalled brick is cut out and replaced.
- Rebuild where structure is lostIf the stack above the roofline has lost its structure, that section is rebuilt, and a cap is fitted to keep water out.
Related questions
- Is a leaning chimney going to fall?
- It can, and a leaning stack or one with open gaps is structural. Brick falling from height is also a hazard at ground level. Keep people, pets and cars away from the base until it has been inspected.
- Can a leaning chimney be fixed without a full rebuild?
- Sometimes. If the damage is limited to the top, a rebuild above the roofline may be enough. If the lean starts at the base, the cause underneath has to be found first. The technician can show you what they see and explain the reasoning in writing.
- Should I call a sweep or a mason?
- A lean is a masonry problem, so a mason's skills apply, and a sweep can inspect the flue and liner. One Call Chimney arranges the right independent technician for the problem when you call (866) 576-7943.
- Can I use the fireplace until someone comes?
- No. Until the stack has been checked, treat it as unsafe. A shifted chimney can have gaps or a damaged liner that let smoke and gases into the house.
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