A chimney stack stands on top of the roof, exposed to wind, rain and frost from every direction. The mortar between its bricks takes a lot of punishment, and over time it breaks down. Repointing replaces the damaged mortar and restores the stack's resistance to the weather.
Signs the pointing needs attention
Look for mortar that is crumbling, recessed or missing between the bricks, and for loose or cracked bricks. A stack that leans slightly, or one that sheds fragments into the garden, needs urgent attention. Inside the house, damp patches on the chimney breast can mean water is soaking through failed mortar.
What repointing involves
The loose and decayed mortar is raked out to a suitable depth, and the joints are cleaned. New mortar is then pushed in and finished neatly. The mortar mix matters: it should be compatible with the bricks, and for older properties a softer lime-based mix is often more suitable than strong cement. Using a mortar that is too hard can damage old brick.
When repointing is not enough
If bricks are badly eroded, or the stack is leaning or unstable, rebuilding the upper part is safer than repointing. A roofer can look at the stack from a safe position and advise. Access normally needs a scaffold or a tower, because the work must be done safely.
Do it with other work
Repointing is often done at the same time as renewing flashings, flaunching and pots, because it makes sense to deal with the whole stack in one visit. That also saves paying for access more than once.
For chimney work, see our Chimney Repairs section or call 07766 547309 for a free quotation.
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