HELP!Would loose chimney flashing cause damp patches downsta

23 Aug 2010
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United Kingdom
Hiya everyone,

Hope someone can help us as we are at a loss. Basically we have 3 damp patches on a couple of walls downstairs (2 around 1 meter high, the 3rd near the bottom of the adjoining wall), either side of our chimney breast and one on the adjoining wall. The damp problem is a lot more evident when it rains but there is no evidence of damp upstairs around the chimney breast. We have had a few quotes from damp proofers, 1 said it is damp, a second one said it's not damp, that it was too wet to be damp and that the problem would be a leak from a roof! So we asked a couple of roofers, 1 said yes it would be the loose chimney flashing causing the damp patches, another said it would not be the chimney as if it was the chimney then upstairs would be damp around the breast too (which it isn't).

Anyone got any ideas?

Thanks for any help

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Is the chimney in use? Is it on an external wall?

Typically, a leak from the roof would show up nearer the roof than the ground floor

A roof leak would not normally enter the chimney and run down, but an unused chimney, or one with defective pointing could allow this.

If you say that this damp is worse after rain, then you need to investigate around the base of the chimney first. If your house does have a DPC and DPM, then its normal for the chimney not to have one and so damp can come up just around the breast

Can you post a picture of these stains, as its possible to identify the likely cause by the type of staining - something from about 3m away showing the wall and staining in context
Hiya mate,

No, the chimney breast is not in use and yes it is on an external wall. I have had a quick look from the ground and the flashing does seem to have come away slightly from the chimney.

I will put up some pictures now.

Thanks alot

Those are very localised patches, which are more typical of moisture coming directly across the wall.

The left picture looks like the patch is below some stairs (the boxing) and is a bit too far from the chimney for that to be the first suspect.

The right picture is unusual as it is too precise and too level - are there any signs that that is an old window or something there?

If this is a solid wall (no cavity), you may want to look externally upwards from where the damp patches are to check the state of the wall - defective brick or soft powdery/missing mortar, or cracks.

If it is a cavity, then water ingress further up could be running down the cavity and hitting a tie wire or lump of something bridging the cavity and coming straight across to the inside. If that is the case then it may be necessary to remove some bricks externally to check for and remove any cavity bridge

Unused chimneys should be capped, but vented top and bottom. So if yours is not, then there is a possibility of condensation or rain soaking the inside. Now this can creep across the wall, but normally you would see stains in line with the flue first and not that far away from the breast, so this is only something to investigate after confirming that there is no other cause

If flashing is lose then it should be replaced in any case. It is a possibility that is could let water run down the walls, but you would normally see dampness right under the roof first, not this far down
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Hi, I'm new to this forum but had a similar problem in a rental property I own. It was on an external rendered wall, I had chimneys fixed, roofs fixed and so on for years and years, but to no avail and at a cost of a couple of thousnad punds. Turned out it was nothing more than internal condensation and nothing to do with outside elements! Lack of air circulating around the room was the cause. I think it is condensation as it looks identical to the problems I was having. p.s. Do you have double glazing?

Eventually, I discussed it with a friend of mine who is a structural engineer, he put me in touch with the owner of 'The Condensation Centre', The Highway, New Inn, Pontypool.

Look this guy up, he sorted my property out and I know he would be happy to offer you advice over the phone as you are not in the area. He will know someone in your area who can help. It cost me about £400-500 by the time I had hacked off, treated the areas, re-rendered with his additives...

I was a very very happy customer. Good luck, let me know how you get on.

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