Increasing damp circles in new plaster, internal wall

[HJJ]

We had this internal wall plastered several months ago. The wall is between our kitchen, which is being renovated, and a new bathroom under the stairs. Pipes have been laid under the bathroom floor for the sink and toilet.

The first circle and blob appeared shortly after the pipes were laid. The builder said hopefully they'd dry out. Several months later there are more (shown in attached photos). Our builder and plumber don't understand where the damp can be coming from as the pipes are just under the floor.

We want to get the wall painted soon, but don't want the plaster to crumble under the paint. I'm sure it will spread further.

Any ideas where it's coming from, and what do we need to do to resolve it? Thanks

 

[Mr Chibs]

So this is an internal wall, can you take some photos of the other side as well please.

Is there any pipework in this wall? or is it all under the floor?

 

[JohnD]

Is it a concrete floor?

 

[HJJ]

So this is an internal wall, can you take some photos of the other side as well please.

Is there any pipework in this wall? or is it all under the floor?

This is the wall the other side

 

[HJJ]

Is it a concrete floor?

Yes it is concrete.

 

[Mr Chibs]

Sorry, thought you said it was a bathroom behind the wall?

Where is the bathroom in relation to the damp patches?

 

[HJJ]

Sorry, thought you said it was a bathroom behind the wall?

Where is the bathroom in relation to the damp patches

Sorry to be confusing. It's a downstairs toilet (room) that contains a sink and toilet. The wall with the blue circle is the other side of the wall with the damp circles. The toilet is opposite and sink is on the back wall, as shown.

 

[JohnD]

Yes it is concrete.

You may have this happening. Does it fit what you know?

A pipe or drain is leaking in or onto the concrete floor.
The wet concrete is not noticed because it is covered with tiles or sheet plastic

On the floor a wall is built, of lightweight concrete blocks. The flocks are foamed and full of pores, which suck up the water by capillarity.
The wet blockwork is not visible because it is concealed by drywall or cladding

Fixed to the wet blockwork is plasterboard , by dot and dab
The dots and dabs provide a path for water to pass from the wet blockwork, into the plasterboard. Because the water is passing at particular points, the wet patches are round, with the centre positioned at the wet dots or dabs

If these conditions apply, the essential action is to trace, locate and repair the leak. Nothing else will cure it.

 

[HJJ]

Thanks very much. The wall is not a new wall, but they have put new concrete over the pipes from the sink, which were put under the floor. I'll show this to our builders, there could be a leak under there without us knowing.