Why is my chimney leaning away from the house above the roofline?
A chimney that leans above the roofline is almost always a mortar problem: the joints on one face have eroded faster than the others, so the stack settles unevenly and tips toward the weaker side. The exposed section above the roof gets weather on all four sides and has no building around it to hold it straight, which is why the lean starts there and not lower down.
Phones answered around the clock · free estimate
Stop using the fireplace until someone has looked at it. A leaning stack can shed brick, and the same open joints that let it move can let flue gases escape where they should not. If anyone in the house has a headache, nausea or dizziness, get outside and call 911.
Why it happens
Mortar is softer than brick and it wears out first. The side of the chimney that takes the most rain and wind loses mortar depth fastest, so that face becomes shorter and softer than the other three. The stack settles into that soft side a fraction of an inch at a time, and once it is out of plumb its own weight keeps pushing it the same way.
Water from the top does the same job faster. A cracked crown or a missing cap lets water run down inside the brickwork, soaking the joints from within. Where the weather freezes, that trapped water expands and pops mortar out of the joints each cycle. Flue gases in an unlined or failed-liner chimney add acids and moisture to the inside face, which is why some chimneys lean toward the house rather than away from it.
A lean that continues below the roofline is a different and more serious story. That points to settlement in the footing or the base of the stack, and it usually means a full rebuild with a proper footing rather than work above the roof only. The technician will be able to tell you which one you have by sighting the stack against the wall and checking the brickwork at every level.
What you can check yourself
Sight it from the ground, from two sides
Stand back and compare the chimney against the corner of the house or a door frame. Walk around and look from a second angle, because a chimney can look straight from one direction and clearly out of plumb from another.
Look for the gap at the roof
Where the chimney meets the shingles, a lean usually opens a visible gap on one side and closes it on the other. Widening daylight or a lifted flashing edge is a strong sign the stack has moved.
Check the ground and the gutters
Sand-coloured grit, loose mortar or pieces of brick near the base, in the gutters or on the roof below mean the stack is actively shedding material. Keep people and cars away from that side of the house.
Look at the chimney breast indoors
New cracks in plaster beside the chimney, stains on the ceiling where it passes through, or a gap opening between the chimney and the wall are worth photographing and dating.
Test your alarms
Press the test button on every smoke and carbon monoxide alarm in the house, and make sure there is a carbon monoxide alarm on the sleeping level. Leave the fireplace unused until the chimney has been inspected.
When to call a technician
A visible lean is already past the looking-and-listening stage. Call once you can see it out of plumb, once brick or mortar is coming down, or once the gap at the flashing has opened. Do not use the fireplace under a stack that is leaning or shedding brick, and do not go up on the roof to inspect it yourself.
Rebuild work is often permitted work, and in some places a structural rebuild down to the footing needs a permit and an inspection. Rules vary by state, city and county, so check with your local building department, or ask the mason doing the work what their jurisdiction requires. One Call Chimney arranges the visit with an independent sweep or mason anywhere in the fifty states: one call to (866) 576-7943, a free estimate, and the price agreed before any work starts.
What the technician will do
- Inspect and photograph what is failingThe inspection covers the stack, the crown, the flashing and the flue, with photographs of each problem area. Ask to see the images and ask for the reasoning in writing.
- Rebuild above the rooflineThis is the usual answer for a lean that starts at the roof. The stack is taken down to sound brickwork and rebuilt plumb, with the brick and mortar matched as closely as the house allows.
- Full rebuild where the structure has goneIf the lean carries below the roof or the base has moved, the rebuild goes further, with a proper footing and new flashing where the chimney passes through the roof.
- New crown, cap and linerA rebuild is the moment to put a sound crown and a cap on top and address the liner, so water and flue gases are not working on the new brickwork from day one.
Related questions
- Can a leaning chimney be straightened instead of rebuilt?
- Brickwork that has tipped cannot be pushed back into line, because the joints holding it have already failed. The sound answer is to take the leaning section down and rebuild it plumb on solid brickwork below.
- Is repointing enough, or does it have to come down?
- Repointing works when joints are eroded but the stack is still straight and the bricks are sound. Once it is visibly out of plumb, new mortar on the surface has nothing stable to hold, and a rebuild of that section is the lasting fix.
- What makes one rebuild cost more than another?
- Access and height drive a lot of it, along with how far down the sound brickwork starts, whether the crown and flashing are included, what the camera finds in the flue, and how closely the brick needs to be matched. The technician inspects first and gives you the price before any work begins.
- Can I still use the furnace or water heater if they vent into that chimney?
- Tell the technician that an appliance vents into the chimney when you call, because that changes the urgency. Until it has been checked, keep carbon monoxide alarms working, and if anyone feels unwell get outside and call 911.
Get a technician out
Free estimate. The price is agreed before the work starts.
Or send us a message
Leave your details and what is going on, and someone from the team will call you back.
More from One Call Chimney
Keep reading
One Call Chimney arranges the visit; the technician does the work and gives you the price.