Damp plaster around pipes - what do I do?

[jw17835]

Started scraping paint off the kitchen walls and realised previous owners covered some mould with a piece of wood. Upon removing realised there are 2 pipes (from mains water to upstairs) running in the plaster. These must've got condensation on or something cause the plaster scrapes away incredibly easy - can be scored with a fingernail. I don't think it's a leak as the plaster isn't soaking but areas of the pipe are green so could be corroded.

What should I do? Remove all the plaster around them and box it in some MDF?

 

[Stanley services]

Hi there. The damp plaster appears from the picture to be undercoat plaster. Commonly known as bonding. If the moisture content in this substrate is too much it will have to be hacked back to the bare brick before remedial works can begin. Unfortunately a dehumidifier would take too long to dry it out.
as for the cause of the water ingress. It appears to be one of two things. Either a gradual leak from the exposed pipe over time, or gradual water ingress from failed or cracked render or pointing from outside.
once you have hacked the bonding off. Put a dehumidifier next to the wall to draw out any remaining residual moisture. Coat the exposed brick work with diluted pva, check the pipe is not leaking and fix if so. Then either get a preservation specialist to sand and cement, (tank) the wall then plaster with multi finish plaster. If you can’t afford this, boxing the pipe in then may be your only option. Hope this makes sense.

 

[piglet11]

Not your fault, but burying any pipes directly into concrete, plaster etc. is a bad idea for lots of reasons - drilling into, nailing into, difficult to repair etc.
Pipes should either be covered with steel channel or run in conduit/ducting.
Hot water pipes also need to move with expansion/contraction.
Failing that, run exposed or box in. Looks as though you already have one exposed.
The other possibility is copper pipes corroded by alkaline plaster/concrete. Alkaline water supplies can corrode from inside the pipe.
You need to clean up the pipes as best you can to determine if there's a pinhole leak - does happen, seen a few. They have a tendency to grow.
Check for leaks with a paper towel. In particular, check any joints
Cold water pipes can drip with condensation if exposed to humid air.
Whatever the outcome, water will do a lot of damage if left.
A plumber mate of mine would probably rip the old pipes out and replace - always quicker