Help identify source of leak

[mkbear]

Hi there

But misleading as it's impossible from a photo but I was wondering if anyone had suggestions on how to investigate the source of what is causing the section circled in red to be damp without hopefully having to rip up the room next door

It's in the cupboard with a boiler next to bathroom. All in the basement part of the converted flat which is tanked and this is not an external wall. The damp is from the bottom upwards and further along away from the wall is dry.

The room on the left of the wall is the bathroom. That wall is fully tiled. Which was renovated in February and there is a bath with a free standing tap.

 

[Deleted member 317380]

I would investigate the solvent welded joints, the bath sealant between bath and wall, under the bath for a start.

 

[jj4091]

If the bath is directly behind that plasterboard get an endoscope that you can attach to your phone then drill a hole through the plasterboard ( presuming it's not tiled on the other side) to inspect under the bath for leaks.