The short answer
Often, yes. A cracked brick or stone can be cut out and replaced, and open joints can be cleaned out and filled again. A stack that leans, bulges or shows cracks running right through several courses has usually moved, and repair alone will not hold it; that points to a partial or full rebuild. A roofer needs to look closely, from a safe platform, to say which applies.
Reading the crack: joint, brick or stack
Cracks in a stack fall into three groups, and each is treated differently.
Cracks in the joints
A stepped crack that follows the mortar between bricks, or stone joints that have opened and crumbled, usually means the pointing has failed. Rain gets in, freezes and widens the gap. This group costs least to put right and is the one most worth catching early.
Cracks through a single brick or stone
A split brick or a stone that has spalled (lost its face in flakes) is a local failure. Frost acting on a saturated unit is a common cause, and so is a pot or flaunching that has stopped shedding water. The unit can be replaced without disturbing its neighbours.
Cracks through the structure
A vertical crack that runs through several courses, a stack that leans or a face that bulges tells a different story. The masonry has moved, perhaps from failing mortar on the flue side or wind loading on a tall, slender stack. This group is the one our chimney stack rebuild guide covers.
How cracked bricks and stone are put right
For a brick that has split, the roofer cuts out the damaged brick and the mortar around it with care, so the bricks beside it are not loosened. A replacement brick of matching size, colour and texture is bedded in new mortar, and the joints are finished to match the profile of the rest, so the patch does not announce itself from the road. On old stacks the match matters. A hard modern brick set among soft old ones will survive the weather better than its neighbours, which can push water behind them.
Stone is handled in the same way, except the replacement is cut or chosen to suit the original, and the mortar is lime-based so that water can leave through the joints and not the stone. In Stroud, where stone and old brick stacks are common, that like-for-like approach is the norm on older houses. Our note on the best mortar for chimney repairs covers the mix.
Where a crack is wide and the masonry either side is sound, stainless steel bars bedded across the joint can sometimes stitch it, but they are a measure for specific cases and we would look at the cause first rather than hide the symptom.
Repointing a cracked and open stack
Repointing is the fix when mortar rather than masonry is the weak point. Crumbling mortar is cut back far enough for new mortar to bite, the slots are brushed clean and dampened, and fresh mortar is packed in and finished to match. Done properly, that makes the stack weathertight again and stops the cracks letting in more water.
According to MyBuilder (2026), repointing a chimney averages about £750, within a range of £500 to £2,000. A bungalow stack is listed at £200 to £700 and a semi-detached house at £600 to £1,500, depending on where the stack sits and how far up the roof it rises. These are national guide figures, not our prices; yours arrives in writing after the survey.
Repointing alone is not enough where the bricks themselves are crumbling. If that is the case, the quote covers both the brick replacement and the repointing.
When cracking points to a rebuild
Some signs say repair will not be enough. These are the ones we weigh at the survey:
- a stack that visibly leans, or has done so more than it did a few years ago
- vertical cracks running through several courses of brick
- bricks or stones that are loose enough to move by hand
- a face that bulges outward
- pointing and brickwork that crumble together, so there is little sound masonry left to repair into
MyBuilder's guide gives a rebuild a range of £2,000 to £10,000 or more, which is why we would rather explain the choice than push you to either end of it. A rebuild is often a sensible answer to a stack that has failed through its whole height, and a poor one for a stack with a single cracked brick.
If the stack leans, that alone is reason enough for a closer look. Where you are not sure about its condition at all, ask us to look before choosing a repair.
What happens after the repair, and what causes the next crack
Cracks come back when the cause is left alone. A chimney with a failed flaunching, a leaking back gutter or a pot that is cracking itself will keep letting water into the stack, and the masonry will crack again. So we look at the pots, the flaunching, the flashing and the flue as well as the cracked part itself.
A blocked or damp flue can feed the problem too. If you are noticing smoke, soot or debris, see our guide to checking whether a chimney is blocked.
When we finish, the roof and gutters are cleared and the old masonry leaves with us. Our workmanship guarantee runs for 10 years and is given in writing, while the survey photographs give you a before picture to compare against, which is handy if you want to see how a crack looked when we first saw it. Other stack work is set out under chimney repairs in Stroud sets out the full range of what we do.