Hidden mould is relatively common and it appers with 100% certainty with buildings/flats with cavity plasterboard walls which have suffered with some sort of water damage. Rented properties frequnrtly suffer from this kind of mould problems.

As in my commnet to Kamila hidden mould can be diagnosed by the presence of odours and changes to to the materials sucha s paints and plasterbord. Just look aout for anything od in your house , that should help yoiu pinpoint the source of the problem.

If i remenber correctly it took them about a year to put all the dots together. The problem with some of the leak is that they develop very slowly and sometimes you simpli dont realise that someting is going on because the change is slow. I heared that the family has left the building shortly after getting the survey results which wasn a problem for them as it was a rented accomodation.

Hi Kamila, the best start is to look for any sings of water damage such as most obvious staining, or less obvios suttle colour chaged, paint warting and peeling in extreme cases. I usually start with visual ispection of the whole property basically looking for anything odd. Basic moisture meter can be quire usefull to give you indication of dampness in the walls. Can you smell any mould related odours – damp, musty etc.
If you find a damp wall wich is constructed from plaserboard and backed with mineral wool insulation in cavity than there is a very good chance it is also contaminated by moulds. If your walls are damp but solid (paster to brick) than there is little chance of sub-surface contamination. However wall cavity itself between different layers of brick is a common place for hidden mould to occur. Hope this helps

Sure not a problem, my email is tomas.gabor@yahoo.co.uk

Thanks 🙂