Six Signs of your Building Having Hidden Mould Growth

When you think of moulds in buildings, you probably picture black markings on the wall or on the ceiling. Most often, however, moulds grow out of sight, e.g. in wall cavities, under the floor or behind the wall paper. In this article we describe 6 signs that will indicate that there is hidden mould growth in a building.



Physical reactions to moulds vary very much. Some people experience severe symptoms, while others in the same building are unaffected:


  • Headache
  • Fatigue
  • Concentration difficulties and failing memory
  • Dizziness and nausea
  • General discomfort
  • Irritation of eyes
  • Irritation of respiratory system
  • Coughing and hoarseness
  • Recurring sinus infections
  • Nosebleed
  • Irritation and reddening of skin


If you experience some of the symptoms, and if they are getting better when you are away from the building for longer periods, it is a strong indication of mould in the building.



Many mould species emit volatile organic compounds (VOCs) as a by-product of their metabolic activity, which can be experienced as a “mouldy” odour in buildings. Sometimes, however, a mouldy odour can also originate from bacterial growth in drains.


Previous water damages

If your home previously has had a water damage which has now dried, your indoor climate may very well still be affected by mould. Usually dried out and dead mould does not emit any odour but can emit large quantities of spores and particles, which are believed to cause the health effects experienced by occupants living in mouldy buildings.



It is quite normal for ants to enter buildings in their search of food. If you find ants living under the floor, it can be problematic, as these insects thrive under damp conditions, just like moulds.


Drop in water pressure

If your central heating boiler experiences frequent drops in pressure, it might be leaking water. Even if the leak is minor, a constant build-up of water can be highly problematic and can lead to massive mould growth. Therefore, it is important to check your heater, piping and radiators for leaks.



Discolorations on building surfaces can be caused by moisture, which will lead to mould growth, and by thermal bridges which can lead to condensation and growth of moulds.