Damp issue on chimney breast

jonny_power

In the top room of our victorian terrace, we have a mouldy-damp patch at the top of the chimney stack in the room.

There's a photo link below here:

http://i43.tinypic.com/2h822jn.jpg

When we moved into the house over 2 years ago we thought it was a historic issue and had the room re plastered. However the damp patch came through again. So at the start of 2013 we had a roofer in to check the chimney stack, replace tiles, re point etc etc. They did a comprehensive job (I hope!) and we thought that we'd cracked it. However it's still there. Probably worse then before.

I'm thinking about buying an expensive dehumidifier to really try and dry the room out completely and check that it's not just trapped moisture in the bricks or plaster.

Is this a good idea?

Any other advice for this kind of issue? I don't want to have to pay for yet more works on the roof and they seemed to think there weren't any leaks or issues.

I guess the other thing is to stick a load of sealing paint in the area and re-paint the wall and see if that solves the issue.

GreenSheep

Dehumidifiers are always a good idea anyway. Very good bits of kit.

If you are happy with the work they did I'd suggest that it is condensation.
However I'd be tempted to put a bit of Thompsons Waterseal all over the stack anyway as they are very exposed and, assuming you are good with heights/nibble, you should be able to do two coats (only one is needed but just to be sure) of the whole thing in about an hour for £20.

I really cannot see much of your picture (only looking on my tiny screened phone)

jonny_power

GreenSheep wrote: »

Dehumidifiers are always a good idea anyway. Very good bits of kit.

If you are happy with the work they did I'd suggest that it is condensation.
However I'd be tempted to put a bit of Thompsons Waterseal all over the stack anyway as they are very exposed and, assuming you are good with heights/nibble, you should be able to do two coats (only one is needed but just to be sure) of the whole thing in about an hour for £20.

I really cannot see much of your picture (only looking on my tiny screened phone)

The photo just shows the location of the damp, not the actual patch. When I get home I'll take a proper pic of it.

I don't have long ladders and don't really want to roam around on my roof and so might see if i can find a handyman who fancies doing the waterproofing (and giving the chimney pots another check).

Thanks for your help, will try and find a good deal on a dehumidifier.

GreenSheep

Don't pay a handyman.
Pay a roofer. A little more maybe but you'll know.

Ask if he can see a tray in the stack. If he can't then porious brickwork is a possibility.

paulalde

I'm having the same sort of issue with a property I've recently purchased. Do you know if the flashing was looked at when you had some work done?

Also before the re plastering was done was is treated with anything to get rid of the salts (hygroscopic salts) that build up when damp occurs?

Through research I've learnt that just replastering isn't enough as these salts remain present and can attract humidity/moisture creating a damp patch again.

I think my issues lie with broken down flashing but I'm going to have to treat 3 chimney breasts before re plastering once the source of the damp is sorted.

Alternatively, could anything be blocking your chimney internally around that area? If rain is coming into the chimney (no cowl installed) it could be soaking into the blockage and then soaking into the brick causing penetrating damp. Less likely but still a possibility as the damp is only in one concentrated area.

NewtoDIY

paulalde wrote: »

Alternatively, could anything be blocking your chimney internally around that area? If rain is coming into the chimney (no cowl installed) it could be soaking into the blockage and then soaking into the brick causing penetrating damp. Less likely but still a possibility as the damp is only in one concentrated area.

This is correct. You've got a blocked-up chimney stack there which should have enough external ventilation so as to prevent condensation.


One thought: do you have neighbours next door with a window high up that looks over this wall? If so, ask them if you can take a video/photos of the wall and zoom into the brickwork. We've recently had a similar issue in one room and builders were up on scaffolding repairing chimney dampness etc. The patch that they repaired looks ok but the rest of the wall isn't and so the problem remains. The builders think it is to do with the roof but I disagree and have looked out of the window when it has been raining heavily. I can't see any issue. Having looked at the wall from our neighbours' house, we can see not only various pointing defects, minor cracks or holes etc. but also spalled bricks. The latter is the problem in the area that we have damp. The Victorian bricks used in our house are not very dense and are easily saturated. The only solution to this problem is to have someone go up and replace them. Until we do that, there will always be water/moisture ingress.

jonny_power

Unfortunately there's no way to look at the chimney stack from close up.

The roofers checked the flashings earlier this year and said it looked fine. Might need another one to go up and take a look.

Here's two photos of the actual problem.

http://i44.tinypic.com/14b4302.jpg

http://i43.tinypic.com/10o4scy.jpg

paulsad

Personally I'd bite the bullet hack it all back (it'll have to be done anyway), examine it under wet conditions see if any obvious water ingress see if it dries out before attempting any replastering. Then get another roofer in with brickwork experience to re check everything.