DIY Doctor UK DIY Forums

Hi there.

We purchased a property over the summer this year. On viewing we saw that there was some slight damp on the lower half of the chimney breast.
(see attached images!)
Following acceptance of our offer over the summer, the seller removed the front plasterboard on the chimney breast for some reason (see pictured) and repaired/made good.
Since then, the damp came back, so we had the chimney capped and vented the front of the 'fireplace' (thinking that it must be this after consulting a couple of builders.
We've also sorted the rather lacking dampcourse on the side of the brickwork by adding some space between the outside wall and the driveway outside.
When it rains, the moisture is very visible and glistens and notice on the pictures that it almost matches the pattern of where the concrete on the old fireplace is.

There's also a photo attached of the top of the chimney which appears to be fine and has been inspected without an obvious problem.

Can anyone offer advice on what to check next?
Thanks

Hi pcw8256.
You don’t say whether the chimney is first or ground floor but I suspect first floor. The damp is probably water running down in the chimney. The vent caps fitted on the outer flues should be sealed to the chimney pots because they do not have an oversize drip on them. If the middle flues should also have some sort of weathering cap to stop water ingress - can’t see from your pictures.
It is unlikely but the mortar joints on the chimney stack have been buttered and as you can see this is coming away in places. If capping the flues properly doesn’t solve the problem, repointing may be the next move.
Regards S

Hi, thanks for replying, I realised I didn't get a notification!

The issue is actually on the ground floor..does that help diagnose the problem? Could it be an issue from the ground, and the chimney is a red-herring?

Thanks for the advice on the caps, we had the middles added recently, the outer ones might be sealed but its hard to see from the picture.

The builder who fitted the caps also did suggest re-pointing, but the amount of water and the speed it shows up, makes it feel unlikely that could be the problem - but I am obviously no expert.

Hi pcw8256,
Because the damp patches are appearing above floor level the issue is probably going to be with the exposed chimney and its components. However, when water enters a chimney stack and reaches lower levels the stains are brown from tar deposits in the chimney. Do you know if the chimney flue is lined? If it is this could explain the rapid appearance of damp when it rains.
Regards S