damp / stains coming through new plaster

[rob7475]

I'm currently renovating a house. I've had it rewired and a few months ago, I plastered the chased / around the sockets using bonding and multifinish. In one of the rooms, I've had some bright yellow stains coming through the wall in patches. I've not painted yet so I can try using stain block to cover them up but wondered if anyone knew what they might be.

Also, in one area that I've plastered, theres patch that looks damp. It's on a brick wall that backs onto the house next door so it's not external. The original plaster is lime plaster I think. Could it be the bonding sucking the moisture out of the lime plaster? If so, do I need to rip it off and start again or will it eventually dry out?

Thanks

 

[JohnD]

are these yellow stains on a chimneybreast?

most likely you have a water leak.

post plenty of photos.

both sides of the wall

and above the stains.

 

[rob7475]

I'll take some photo's next time I'm there.

It's not a chimney breast - it's the party wall between this house and next door. At the other side, there may well be a chimney breast though (in the neighbours house).

there's no pipes in the wall or in the room above.

The yellowing isn't what I'd usually expect from damp - it's a bright, almost flourescent yellow

 

[JP_]

might be same problem, no idea if the solutions suggested work ....
https://www.mybuilder.com/questions/v/6850/how-to-stop-yellow-stains-showing-through-painted-plaster