Very basic vent question

22 Feb 2024
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United Kingdom
Hi all

I have an old blocked up chimney breast in my kitchen that has a lot of damp patches on it. I'm looking to install an adjustable vent (something like this) to help but I have an extremely basic question about it, as I've never seen one installed before - what exactly should the vent be covering? Should I knock out a brick? Should I just drill through a couple of holes for ventilation? Something else?
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Take out a brick and look inside. Builders often shovel rubble inside an old fireplace, where it becomes damp. You would have to open it to clean out. Ground floor hearths have no DPM so will wick up damp from the ground.

Each flue needs to be ventilated top and bottom so there is airflow to dry it out. One brick is enough, near the skirting. You should be able to feel the draught. If you are taking the floor up it is possible to dig out the hearth and ventilate the subfloor void up a disused chimneys.

Damp in kitchens is often associated with plumbing or drain leaks. The water supply pipe is usually in or under the floor and leaks after about 50 years. There may be old pipework from an old boiler in the fireplace.

If there is poor ventilation there will be condensation from kitchen activities, especially on cold external walls.

Post some photos of the damp. Show the entire wall.

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