Mould on surfaces within the home is easy to identify it can be seen; it can be cleaned and it can be fixed. When mould growth occurs under the surface of finishes it is much harder to identify and eradicate. Mould can exist for years without being noticed by the occupants and during that time mould spores will circulate throughout the dwelling with the potential of causing health problems.
Moist surfaces that are hidden from view are susceptible to mould growth. These can be cold water pipes behind cupboards or under baths, behind wall panelling, within stud walls, etc. all areas where moisture can accumulate without being noticed. The most likely places are surfaces beside external walls, where moisture can reach its dew point.
Careful design of these areas is required if mould growth is to be prevented. Cold water pipes should be insulated so that condensation does not form on them. Cavity walls must be vented to remove moisture and areas where interstitial condensation can form must be insulated to raise their surface temperatures.
If mould growth occurs, you may not know about it for sometime, but eventually the growth of the mould can reach the surface, where it can be seen and remedial action can be taken.
Areas needing careful attention include showers, where water may penetrate into the walls of the shower enclosure, extract vents that do not vent to the outside and cold water tanks in the attic. If these are left uninsulated water vapour can condense and drip onto the ceiling and create the condition where spores can grow.