I have a damp patch which has appeared on an old chimney breast. The room is on our ground floor and I recently had the house renovated and this damp patch appeared 6 months later. As you can see from the photo the damp is about 30cm across and very localised and the rest of the wall is fine.

I would welcome suggestions on what the cause is and how to fix it.

Sorry..can't open that, Cheapskate that I am I have open office..any chance of attaching a pic or two??

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Verwood Handyman
I Know it says I'm On-line, but I might have just left myself logged in, whilst I'm out....

I'm not going to open an office document either. Not even going to try. It could contain a virus!

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Mike

Open Office scans it for nasties before opening. So here it is , (reduced to a more manageable size).

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One day it will all be firewood.

Do you have any vents on the chimney breast?

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Verwood Handyman
I Know it says I'm On-line, but I might have just left myself logged in, whilst I'm out....

Yes just out of the photo is an air vent which is at a similar height to the damp patch.

More photos needed I'm afraid.
1 showing the whole wall inside and 1 showing the chimney outside if possible please.

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Mike

The chimney is not exposed to the exterior elements as this wall connects to my neighbour's house as my house is terraced.

I'm hoping someone else will jump in with suggestions here because thats a bit od a puzzling one.
Could therebe an old back boiler in behind there all corroded and leaking?
Are there any pipes there or above there or maybe behind there in the neighbours house that could be leaking?
It just seems an odd place for the damp patch if it was water coming down the chimney from damaged flashing or pointing etc.
perhaps someone else will know better?

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Mike

have you spoken to your neighbours they may have a leak they dont know about on thier side of the party wall?

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- Dave
http://www.pamperhouse.net
http://www.invertedcircle.co.uk

That is a strange place for a localised damp patch like that

I have checked in my neighbour's house and they have the same type of old chimney breast on their side too, and there is no sign of damp their side.

This room is on the ground floor and my house is 4 storeys high, so I dont think that water can be entering down the chimney. I do have a working gas fire the floor above.

I have read that that sometimes salts can come out from the wall which were created by gases from the original cole fires. But it seems strange to me that I have only had this problem since my house was renovated and redecorated. I am thinking about having the plaster stripped back in this local area, leave to the air for sometime and then redecorate again. Lets see if that will work....

Hi there,

It could be a patch of hygroscopic salts. In older chimneys the soot etc. can leave deposits in the chimney which draw moisture out of the atmosphere. These migrate through plaster when wet and can draw moisture out of the air (especially when humid).

The other alternatives I can think of are:
1. some source of moisture in the area (eg. leaking plumbing - already mentioned)
2. random patch of different material (eg. bonding plaster) while the surrounds are waterproof render

Either way, I think the solution required is to:
a. hack off the plaster +300mm in all directions
b. apply a tanking slurry (or alternative waterproofing mechanism)
c. make good and redecorate.

Hope that helps,

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Many thanks to all for the advice