Why mortar fails first
Mortar is designed to be the sacrificial part of the chimney — it's meant to wear before the brickwork does, which is exactly why repointing is a normal, expected maintenance job rather than a sign of a serious problem.
Signs it's due
Crumbling or missing mortar between the bricks, a stack that looks patchy or discoloured, or mortar you can scrape out with a fingernail are all signs it's time to repoint before water starts getting into the brickwork itself.
What the job involves
We rake out the old, failed mortar to a consistent depth and repoint with a mix matched to the age and type of the property, since older Bristol stone and brick chimneys often need a softer lime-based mortar than modern cement mixes.