hi all - first time post so bear with me I have an issue with some damp patches that keep appearing on my wall. They come through and then disappear again, usually reappearing after rainfall of when the temp drops. If my fire is on then they tend to go away. There are no obvious cracks outside- in fact, the lower half of the house has been reprinted and the top half is render. I will try to attach a photo - any advice would be appreciated, we have had a couple of tradesman round who fail to combat the problem! We have a similar issue in the upstairs bedroom directly above - we had the outline of where the old fireplace would have been - it was quite spooky!! They just appeared one day. The fireplace has now faded but there are a few spots similar to the photo added.
I'd say it's salts from the year's of burning coal leaching through the brick and render. These salts are hygroscopic and therefore draw moisture in from the internal warmed air. Solution: hack off affected render, apply salt stabilizing solution, render with salt inhibitor and skim the whole wall in to give a decent finish
Removed the whole affected area, dampen area, brush brickwork with SBR/cement slurry (2/1), allow to dry,might need to apply second coat allow, some like it to go tacky, before rendering wall with cement render with SBR added to mix, allow to throughly dry, then finish off with thistle multi finish. The SBR will add a waterproof layer, & should stop the patches appearing.
Thank you all for your your replies. In the meantime, is this causing any damage? Ie. How urgent is it that this is treated? (Other than the hideous marks)
I have attached an image of the bedroom upstairs, not as bad but still a mess. There is an air vent where the old fire place was in the bedroom and downstairs is a gas burner - the chimney is capped just above this as suit was dropped down but it has ventilation at each side. The chimney stack was taken down prior to my purchase and a flue attached (although this flue is now redundant as the gas burner has a horizontal flue)
I have to agree with astramax. Look at simple solutions first like ventilation, condensation build up from the fire, possible ingress of water from the chimney stack. Rather than salt treatments and plasterers I would get a chimney sweep out. They can give you good advice and inspect everywhere without removing plaster etc. Good luck
Even more convinced now re ventilation thoughts, their is insufficient through air flow! You must be very posh having 'suit' in your chimney, in our slum we have 'soot'!
I believe the gentleman that lived here prior to us was very posh - perhaps he used the chimney stack as his walk-in wardrobe?!
It was the chimney sweep who said to cap the chimney at the bottom and that because the flue was horizontal that it didn't require a sweep... Perhaps a second opinion would be in order then?
If it was me personally I would start with a chimney sweep. You aren't wanting anything swept. I just think they will be able to identify what is causing the damp without causing damage. Obviously it is just a suggestion but it seems the obvious place to start as it is definitely IMO associated with your chimney. could just be as simple as more ventilation which a sweep would identify. Hope you get it sorted.
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