Leaking Chimney: Where The Water Gets In

A leaking chimney is nearly always one of four things: the lead flashing where the stack meets the roof, the back gutter behind it, the mortar between the bricks, or the capping and pots on top. The damp patch on the chimney breast or the ceiling beside it does not tell you which. A survey of the stack does, and each one has its own fix.

At a glance

• Most common cause: the lead flashing at the base of the stack
• Also check: the back gutter, the mortar, the capping and the pots
• Water coming in now: ring 087 645 9553, answered 24 hours for emergencies
• The price: free survey, written down before any work

A chimney is a brick column pushed up through the roof, and every side of it is a join. Rain runs down the slates or tiles into the back of the stack, wind drives it into the brickwork, and anything that is cracked or has lifted lets it in. On Dublin houses the stacks are old and exposed, and many sit on a party wall shared with the house next door.

The Four Places A Chimney Lets Water In

• The lead flashing. Lead is dressed into the brick joints and laid over the slates around the base of the stack. When it lifts, cracks or comes out of the joint, water runs behind it and down the inside of the breast. This is the most common cause.
• The back gutter. On the uphill side of the stack the lead forms a small gutter that takes all the water coming down the roof. If it is blocked, split or too shallow, it overflows into the roof.
• The mortar. Weathered joints soak up rain like a sponge, and in a long wet spell the damp comes through to the chimney breast inside.
• The capping and the pots. A cracked capping lets water into the top of the stack, and a pot on an unused fireplace with no cowl lets rain fall straight down the flue.

How Each One Is Fixed

Flashing is renewed: the old lead comes out, new lead is cut and dressed to the stack, wedged into raked-out joints and pointed in. A failed back gutter is rebuilt in new lead with enough depth to carry the water. Weathered mortar is raked out and the stack repointed. A cracked capping is replaced, and a pot on a fireplace you no longer use can be capped or fitted with a cowl. Where the stack itself is leaning or the brickwork is breaking up, Jordan will say so, because then the honest answer is to take it down to sound brick and rebuild it.

What To Do While You Wait

Move anything that matters away from the chimney breast and put a towel or a basin where the water is coming through. Do not go up a ladder to look; the source is on the roof side of the stack and cannot be seen from the gutter. Note when it leaks: in every shower points to the flashing or the pot, only in long driving rain points to the mortar. If water is coming in fast, the mobile, 087 645 9553, is answered 24 hours for emergencies, and the first visit makes it safe.

What Decides The Price

• Which of the four it is. Re-dressing one side of the flashing is a smaller job than a new back gutter and full lead.
• Access. A low stack on a bungalow is reached from the roof. A tall stack on a two or three-storey house may need scaffold or a tower.
• How much of the stack needs repointing, or whether it needs rebuilding.
• Whether the slates or tiles around the base have to be lifted and relaid.

The survey is free and the price is written down before any work starts. One customer's words: "Had a leaking chimney and Jordan and team came out and dealt with it straight away."

Who Does The Work

Delta Roofing is family-run, over 20 years in business, based in Kimmage, Dublin 12, fully insured and members of the National Guild of Master Craftsmen. Every roofer on the crew is fully qualified.