Strange Damp Patches

[POC]

Hello,

I'm encountering some strange damp patches on my wall and I've tried a number of small fixes but had no luck so I thought I'd try here. I'm struggling to work out my next step so any input would be very much appreciated.

It's an old 1890s terrace house and the problem is with one of the party walls. I removed the wallpaper in my hallway and had it skimmed just over a year ago. I'm having problems with unsightly damp patches - see attached pictures. The neighbour on the other side isn't having any similar issues.

They appear after heavy rainfall and they eventually dry out. One of them is about 2m high and the other shown by the dado rail is about 1.25m high. Hopefully it'll be clear in the picture but the 2m high one has developed tiny little holes in the plaster. I'm assuming that the plaster is attracting the moisture from the air as there's no sign of damp above or below it to suggest a leak; however, I'm far from an expert.

The paint eventually started to flake off after a number of cycles of the wall getting damp then drying out. I spoke to the plaster who skimmed it and he initially said it may have been an issue with the first coat of paint I applied not sealing the plaster properly. I followed the suggested water-to-paint ratio on paint bucket, but he thought it could've been down to me not mixing it particularly well.

The same problem happened after sanding it down then repainting with a well mixed and watered-down paint. I spoke to the plaster again and he suggested that it may be just a couple of cold spots on wall and I could try sealing it with damp seal. I did this and it delayed the patches reappearing; however, now they're coming through they seem more pronounced than ever. I've since done a bit of research and apparently applying such a seal can stop the wall breathing and trap the moisture in, and this is bad news for the long-term health of the wall.

The only other thing of note is that this area of the wall also had a DCP installed around 15 years ago. I maybe wrong, but I given that one patch is 2m it is too high to be rising damp.

Once again, any advice the next step I should take would be much appreciated.

Thanks,
Phil

Untitled

• POC
• 13 Oct 2014
• 1

Untitled

• POC
• 13 Oct 2014
• 1

Untitled

• POC
• 13 Oct 2014
• 1

 

[gavingreyling]

this seems like some sort of leakage. if the neighbor doesn't have the same problem, it might be that the leak is only on your side.

since this is a very old house, the roof might not be properly sealed anymore and water is able to penetrate the roof. the water then makes its way down to the wall where it goes into the plaster. this is why the plaster is showing these signs.

to fix this problem, you have to look inside the roof or loft for anywhere there might be a sign of leakage and seal the spot. after that's sorted out, wait for a few heavy rainfalls and see if it's still the same, if not, you can continue.

the plaster seems damaged, which is not good as it will be weak and cause problems if you are trying to cover the wall. you need to break down the plaster until you've reached the end of the damaged plaster, the good plaster will be very strong meanwhile the weak plaster will be easy to break off.

now you can mix plaster with a little bit of bonding liquid (just to be safe) and cover the part you've just broken down. wait for it to dry and place new wallpaper.

 

[POC]

Hi Gavin,

Thanks for the response. I did initially think that it was a leak. I went up into the loft when the patches first appeared and could not see any signs of a leak or dampness. The roof was replaced in the mid 1990s as part of a council-lead urban regeneration project, and the coping stones were also replaced and the parapet wall covered in flashing. It all generally seems to be still in a good condition.

Also, the neighbours have also had a loft conversation since I first noticed the damp spots (i.e. since I removed the wallpaper, had it skimmed and they appeared), and the builders doing the work didn't notice any dampness from a potential leak. The party wall is not a cavity wall either, so I assumed any leak would leave traces in both properties. Again, I'm far from an expert so could be wrong.

I think I'll go up the loft again next time it rains just to make sure I didn't miss anything.

Thanks for the help,
Phil