Chimney Repairs South Wales › Maesteg › Guide
A brown stain or damp wall beside the chimney breast is a common reason people call us on Maesteg terraces. Exposed valley weather means the stack is a likely culprit, but not the only one. Finding the real cause matters, because patching the plaster before the source is dealt with just brings the stain back. Here is how the cause is traced.
Water coming down the stack
A cracked cap, failed flaunching or a loose pot lets rain run down into the flue, where it soaks the brickwork and shows on the breast below. Open joints in the stack itself let wind-driven rain in sideways. In an exposed valley position that can happen after a few hard storms, and the stain often darkens when the weather turns wet.
Pots and cowls that have shifted in the wind are a frequent cause on exposed terraces, and the damage is easy to miss from the street because the water travels down inside the flue before it shows in the room.
Other roof-level causes
Water can also enter at the flashing where the stack meets the roof, through slipped or cracked tiles or slates beside it, or at a gutter that overflows nearby. Flashing and repointing are separate jobs, so we only mention them here: both get checked whenever we trace damp near a stack.
Causes inside the house
Not every damp patch comes from above. An unused flue with no ventilation can hold damp air, cold chimney breasts attract condensation, and salts from old soot can draw moisture out of the plaster and brown it. Leaking pipes or a bridged damp course can also play a part, so we look at the whole picture. A damp patch that appears in dry weather points more towards the inside causes than the roof.
What you can check from inside
From inside, note whether the stain grows after rain and whether the ceiling beside the breast is marked. Where the loft is safely boarded and lit, look at the stack brickwork and nearby timbers for damp. Take a photograph and keep off the roof entirely. Then call us for a proper look.
- Brown staining that comes and goes with the weather
- Damp that stays the same in dry spells
- Salts or powdery marks on the plaster surface
- A musty smell in the room or loft near the breast
How we trace and repair it
We follow the damp from room to loft to stack, checking pots, flaunching, brickwork and flashings in turn. When the cause is the stack, we repair or rebuild what has failed, rebed the pots and seal the top so rain sheds clear. We will also tell you if the cause is inside, rather than guess at it. Let the wall dry before redecorating.
Need a chimney looked at in Maesteg? See chimney repairs in Maesteg, or for the lead and mortar side of it, chimney flashing repairs and chimney repointing and repairs.
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Common Questions
Should I just paint over the damp patch?
No. Paint hides the stain for a while but does nothing for the cause, and damp trapped behind it can spoil the plaster further. Find where the water is coming from first, repair that, let the wall dry, and then redecorate.
Can the chimney cause damp when it is not in use?
Yes. An unused flue still lets rain in if the cap or pots have failed, and without a fire to warm it the damp stays. A properly fitted, ventilated cap or cowl on an unused stack helps keep water out while letting air move.
Is a damp chimney breast dangerous?
It is usually a nuisance rather than a danger, but a stack that lets in water may also be loose or failing. Keep clear below it if you can see movement or loose bricks, do not use any fire or stove connected to it, and call us for a look.
Get a Chimney Looked At in Maesteg
Tell us what the roof is doing in Maesteg and we will look at it. Call 07766 547309, message us on WhatsApp or use the form below.