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Chimney Flashing: Where the Stack Meets the Roof

Chimney flashing is the lead that seals the joint between the stack and the roof. A reseal or a small repair costs €250 to €800, and renewing the lead round one chimney costs €400 to €1,800. It is the commonest cause of a leak at a chimney: the lead lifts, splits or comes out of the joint it is tucked into, and rain runs down the stack and under the slates.

The four parts of the lead, how each fails, and what a proper repair is.

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  • €250 to €800a reseal or small repair
  • €400 to €1,800new lead, one chimney
  • 4 to 6 hoursonce the access is up

Irish chimneys, seen from the roof

Real roofs, photographed by the Irish company working on them.

a rendered chimney stack with cowls on its pots and lead flashing at its foot, on a slate roof in Co. Meath
A rendered chimney on a slate roof in Co. Meath, seen from the ridge: cowls on the pots, a lead apron at the foot. A real roof job.
a worker on a slate roof between two rendered chimney stacks with lead flashing at their feet
Two rendered stacks on an Irish slate roof during a roof job. The lead at the foot of each stack is where most chimney leaks start.
The foot of a rendered chimney stack on a slate roof, with its lead flashing
The foot of a rendered stack on an Irish slate roof. The lead here keeps the water out of the house.

The four parts

PartWhere it isHow it fails
ApronThe front of the stack, facing down the roofLifts in wind, splits with age
Side flashing and soakersStepped up each side of the stackMortar falls out of the chase and the lead comes loose
Back gutterBehind the stack, where water and leaves collectFills with moss, corrodes, overflows under the slates
Lead trayBuilt through the stack, on newer chimneysMissing on most older stacks, so damp tracks down inside

Signs it is the flashing

  • A damp patch on the ceiling right beside the chimney breast.
  • It shows during rain or within hours of it, and worse with wind from one side.
  • From the ground: lead standing off the stack, or a line of grey sealant where lead should be.
  • In the attic: a wet rafter or a stain on the felt beside the stack.

A proper repair, and a patch

A proper repair is new lead, dressed to the roof, stepped up the sides and tucked into a chase cut in the stack, then pointed in. On slate, soakers go under each slate beside the stack. It lasts as long as the roof.

Flashing tape, a bead of mastic or a coat of paint-on sealant is a patch. It can buy a winter. It will not last, and it makes the proper job slower because it all has to come off.

Flashing, priced

JobTypical costWhat moves the price
Flashing resealed, or a small repair€250 to €800One side lifted or a split in the lead
Lead flashing renewed round one chimney€400 to €1,800Slate or tile, a back gutter, how much lead
Repointing, flashing and flaunching in one visit€700 to €1,600One scaffold for all three
Scaffolding for a chimney€350 to €1,200Two storeys or three, a stack at the ridge or the eaves

Repair work on a house is at the reduced 13.5% VAT rate. Ask for a written price that includes it, and says whether scaffolding is in it.

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More on chimney repairs

Costs, leaks, mortar, flues and rebuilds.

Two brick chimney stacks with clay pots above a white gableWhat chimney repairs costEvery job, priced. Repointing is €300 to €1,500.A rendered chimney stack with lead flashing at its foot on a slate roofA leaking chimneyWhere the damp shows tells you where the water gets in.An old brick house with a brick chimney at each end of its roofRepointing a stackWhen new mortar is enough, and when it isn't.A period house with a chimney and pots at each end of its slate roofLining a flueFor stoves, tar and cracked flues. €800 to €2,500 fitted.A long slate roof with two rendered chimney stacksRebuilding a stackA lean, bulging or loose bricks. €800 to €2,000 above the roofline.A row of houses with slate roofs and tall brick chimney stacksCapping and cowlsAn unused flue capped with a vent is €300 to €900.

Chimney repair in every county

Check your chimney

Four taps: what's wrong, the height of the house, what the stack is built of and what it's used for. You see the likely job and our price for it. Your number is only asked for at the end, if you want one chimney repair company that covers your county to ring you.

What's wrong with the chimney?

Pick the nearest. A guess from the ground is fine.

Questions people ask

How long does new flashing take?

Four to six hours for one chimney once the access is up.

Is lead still the right material?

Yes. It shapes to the roof, moves with heat and lasts for generations. Lead-free alternatives exist and are fine where they are fitted the same way.

Can flashing be repaired without scaffolding?

On a bungalow, often. On two storeys it needs proper access to be done right.

The leak only comes with wind from the south-west. Why?

Wind drives rain up under lead that has lifted on that side. It is a flashing fault, not the slates.

Will sealant fix it?

For a while. Ask for lead.

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