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Chimney leaking: the four ways in

A chimney is a brick tower standing in the weather with a hole down the middle, and it can let water in at the top, through its sides and where it meets the roof. Damp on a chimney breast is one of the commonest calls we get, and the fix depends entirely on which of those routes the water is taking.

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Signs to look for

  • A damp patch or staining on the chimney breast, often in a bedroom
  • Water around the base of the stack in the loft
  • Brown marks on the ceiling beside the chimney after rain
  • Cracked or missing mortar around the pots at the top
  • Lead flashing that has lifted away from the brickwork
  • Soot-stained damp in an old fireplace that is no longer used

What causes it

The flaunching, the sloped mortar cap around the pots, cracks with age and lets water straight into the top of the stack. An uncapped pot on a flue nobody uses lets rain fall straight down it.

Brickwork with perished pointing soaks up water like a sponge, and on a tall stack that water ends up inside the house. The flashings, the lead where the chimney meets the roof slope, lift, split or come away when the mortar holding them fails.

Damp on a chimney breast can also be salts from years of burning fuel drawing moisture out of the air. That is not a leak at all, and we will tell you if that is what we see.

What we do

We look at the stack from the roof and the breast from inside, and work out which of the routes is the one in use. Often it is more than one. You get photographs of each and a price that lists them separately.

Typical work is re-flaunching the top, fitting a ventilated cap to redundant flues, repointing the brickwork and renewing the lead flashings with properly dressed and fixed lead. If the stack is unused and in poor condition, taking it down below the roof line can be the better long term answer, and we price that too.

What it usually costs

Chimney work nearly always needs safe access at height, usually a chimney scaffold, and that is a fair part of the cost. The work itself depends on how many of the four routes need attention. We price after a free visit, with access and each repair shown as separate lines so you can see what you are paying for.

Questions

Can you fix a chimney leak from a ladder?

Not safely, in most cases. A chimney is usually at the highest point of the roof, and proper work on the flashings or the top needs a stable platform.

Should I remove a chimney I do not use?

Sometimes. Capping and ventilating it is cheaper; taking it down below the roof removes the maintenance for good. We price both so you can choose.

Why is there still damp after the chimney was repaired?

Brickwork can take weeks to dry out, and salts left in the plaster keep drawing moisture. If it is still wet after a few dry weeks, we come back and look again.

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