Chimney Repairs, Rebuilds and Removal in South London

Everything above the roofline is exposed masonry. Water soaks into soft London stock brick, sits there, and expands when it freezes, taking the face off the brick and opening the joints. The higher and the more exposed the stack, the faster it goes — a tall stack on a three-storey terrace weathers harder than the same brickwork four metres lower down.

There is a second mechanism most people have never heard of, and it is the one that makes stacks lean. Years of coal and gas leave sulphates in an unlined flue. Damp carries them into the mortar, where they react and the joints slowly swell. Because one face of the stack stays wetter than the others, that side grows more, and the stack bends away from plumb — usually towards the weather side. A stack that leans is not a pointing problem. The mortar has gone all the way through and it wants rebuilding.

The third cause is a previous repair. Someone repoints a Victorian stack in a hard sand-and-cement mix, and water that used to escape through the soft joint now has nowhere to go but through the brick. The faces blow off a course at a time. On London stocks the mortar should be weaker than the brick, not stronger, which normally means a lime-based mix.

Almost every stack we attend needs some combination of the following. None of it is exotic work. It is careful bricklaying and careful leadwork, done at height, and it is the leadwork that most jobs get wrong.

A damp patch on a bedroom ceiling near a chimney breast is almost never coming through the bricks in a straight line. Water gets in at the top through cracked flaunching, or at the roof line through failed lead, then runs down inside the stack or along a rafter and appears somewhere else entirely. Chasing the stain rather than the source is why some chimney leaks get half-fixed for years.

The four we find most often are a cracked cement fillet where lead should be, a back gutter that has split or silted up behind the stack, missing soakers on a stack that has been re-roofed around, and a stack so saturated that it is simply wet through. The last one is worth naming because no amount of sealant fixes it — it needs the pointing and the flaunching sorted so the brickwork can dry.

There is also a leak that is not a leak. A capped, unventilated flue in an old house condenses inside and stains the breast in patterns that look exactly like rain coming in. We check for that before selling anyone a stack repair.

The test is how deep the failure goes, not how bad it looks. If the bricks are sound and the joints have weathered back, that is repointing and new flaunching — a day, and the stack has another twenty or thirty years in it. If the brick faces are spalling across several courses, or the stack is visibly out of plumb, the mortar has failed through the full thickness and repointing it is money thrown at a wall that will move again.

Rebuilding above the roofline costs more than repointing but far less than most people expect, and it resets the clock. Taking the stack down instead is the cheaper option and often the sensible one on a house where nobody has lit a fire since the 1970s — but it changes the look of a terrace, and on a shared stack it is not a decision you can make on your own.

If we are already re-roofing the slope, the honest advice is to deal with the stack while the scaffold is standing. Coming back to a chimney on its own means paying for the access twice.

Removing a stack down to below the roofline is roofing work: the brickwork comes down, the hole is closed with new rafters or noggins where needed, the roof is re-slated or re-tiled across it and the flue is capped and vented below. One to two days on a terrace, plus the scaffold and a skip.

Two things stop people mid-job. The first is that most London stacks sit on the party wall and are shared with next door — half a stack cannot come down without agreement, and it normally means a notice under the Party Wall etc. Act 1996 and a conversation with your neighbour before anything is booked. The second is building control: taking out brickwork that carries load, or that supports a neighbour's flue, is notifiable, and on anything structural you need a structural engineer's drawing before a council or an approved inspector will sign it off.

Removing the chimney breast inside the house is a different job again — steelwork, plastering, ceilings, and Part A of the Building Regulations. We will tell you plainly whether what you want is a roof-level job or a structural one, and we do not pretend the second is a morning's work.

We are roofers and bricklayers. We do the stack, the weathering and the roof around it. We do not line flues, fit stoves or gas appliances, or sign off flues for use — that is HETAS and Gas Safe territory and we hold neither. If you are bringing a fireplace back into use, get it swept and tested by someone who does, and let us do the masonry.

We do not sweep chimneys either, and we will not quote for a stack we have not looked at. Photographs from the pavement do not show a back gutter or the state of the joints on the far face. The survey is free; the guess would not be worth having.