Hello,

In our house we have a wall where behind there is a sewer pipe running through an open vertical space. Last months have appear 2 stains that we think are due to humidity: first one is yellow and has stopped after some weeks, second one black and even when it does not grow is becoming darker and darker.

Without opening the wall, do you think is posssible to assess whether these stains are due to a leakage or to water condenation in the open space?

Thanks,

Barbara

Hi Barbarar,
IT could be either, but if you can call in a professional who deals with these sorts of things, then they've usually got a meter that they can measure whether you have damp inside the wall or it's down to condensation.
They will also drill a few small holes in the wall... outside preferable... to see if you have any wet in your cavity wall which is where the damp could be eminating from.