Leaking Chimney: Find Where the Water Gets In

A chimney leaks in one of four places: the lead flashing where the stack meets the roof, the mortar joints or render on the stack, the flaunching round the pots, or straight down an open pot. Where and when the damp shows inside tells you which. Two things look like leaks and aren't: tar soaking through from the flue, and condensation in a flue that has been sealed.

Read the damp from inside the house before anyone goes up.

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Free, no obligation. One local company prices it, not five.

4 ways inflashing, joints, flaunching, pot
€250 to €800to reseal flashing
€700 to €1,600all three repairs in one visit

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.

Where the damp shows

What you see	The likely cause	The fix
On the ceiling beside the chimney breast, during rain	The lead flashing	Flashing: €250 to €800 to reseal, €400 to €1,800 for new lead
On the chimney breast upstairs, a day or two after rain	The mortar joints or the render	Repointing: €300 to €1,500
Drips or wet soot in the fireplace	Rain straight down the flue	A cowl: €100 to €450
Damp high on the breast, right under the roof	Cracked flaunching round the pots	Flaunching: €200 to €1,200
Brown or yellow stains that don't follow the rain	Tar from the flue, not a leak	A liner: €800 to €2,500
Damp on a breast with no fire under it	A sealed flue with no airflow	A vented cap: €300 to €900

A rendered chimney stack with cowls on its pots and lead flashing at its foot, on a slate roof — A stack on a slate roof in Co. Meath. Flashing, joints, flaunching and pots are the four ways in.

Check from the attic first

Go up with a torch on a wet day. Look at the timber and felt round the stack. A wet rafter or a run mark beside the chimney is the flashing. A damp stack with dry timbers round it is the masonry or the top. A dry attic and damp only in the room below points to tar or condensation, not rain.

Why it gets worse fast

Water in a stack does damage twice: once as damp, and again when it freezes and opens the joint that let it in. Rain also arrives sideways here. Castlebar in Co. Mayo gets 1,458 mm a year and Tralee in Co. Kerry 1,357 mm, most of it on a south-west wind. A fault that drips this winter stains a ceiling next winter and rots a rafter after that.

Leak repairs, priced

Job	Typical cost	What moves the price
Flashing resealed, or a small repair	€250 to €800	One side lifted or a split in the lead
Lead flashing renewed round one chimney	€400 to €1,800	Slate or tile, a back gutter, how much lead
Repointing a chimney stack	€300 to €1,500	The size of the stack, how deep the joints have gone, the access
Flaunching renewed, pots re-bedded	€200 to €1,200	How many pots, and whether any are cracked
A cowl supplied and fitted	€100 to €450	The type of cowl and how it's reached
Repointing, flashing and flaunching in one visit	€700 to €1,600	One scaffold for all three