damp patches

[hopkinsd]

hi can you please help
i did some work at my mums house and found a large bulge in the plaster on a chimney breast so i knocked it off and re plastered best i could .
no a couple months down the road it has come back as a damp patch. what can i do. i have been on the roof the chimney pots are capped off the chimney breast is dry in the attic and dry in the bed room.
the damp is about four and a half feet off the ground how can i solve this problem as it is starting to ruin the wall paper i just put up at 18 quid a roll. i have tried to upload photos in an attachment please help.
a local builder said its a cold spot in the wall that will go away should i believe him.

please please help
Dave

[hopkinsd]

the bottom pic is after i plastered the wall and it had dried out for a week. also there is the same in the alcove to the left of the breast that i repaired in the same way hacking it all away then replaster it .I did not hack off the complete walls just where it was crap as the rest was sound dry and solid after unibond i used carlite to fill the holes then skimmed the complete walls with finnish plaster.
I am not a tradesman but can put my hand to most things but i do think i was out of my league when i started this but my mum did not have the money to pay a pro as she was recently widowed due to my dad falling ill . i hope someone can give me some advice
thanks again Dave

[hopkinsd]

WOW what a great useful site 345 views no reply's
makes me think what kind of tradespeople are on here
you would think that one real builder would have a idea
should call this sit dodge city or boot hill
oh look its BILLY THE KID AND HIS COWBOY MATE JACK THE LAD

[Makitisi]

Hello
I don't know what a 'cold spot' is -
as for the damp patch the water must either be getting in somehow from above or bridging from behind - you've checked the chimney, pointing and flashings? It could be rain seeping in somewhere then dripping inside the chimney onto something at the level of the damp patch. Or possibly something the other side of the chimney - is it still your property or a party wall to next door? Alternatively it could be a leakage from a pipe - water / central heating / drainage / overflow etc [i've just repaired a damp patch caused by a hidden plasterboard nail inserted at least 15 years ago which didn't show until their boiler was replaced last week increasing the hot water pressure]. The 3rd cause could be that once there has been dampness for some time salts tend to accumulate at the surface drawing moisture in from the air.
Render the patch - allowing for extra wide margins - with a strong mix [3:1] of sharp [e.g. leighton buzzard] sand and cement [with waterproofer as an added precaution] you'll stop further ingress of moisture, but if water is still accumulating it will track somewhere else instead.
When you replaster on top of the render make sure there is no bridging - plaster directly on brickwork acts as a wick.
good luck with your detective work