Why is mould growing in my home?

In the end, mould will consume everything – even you and I

Moulds are living organisms, and part of the natural environment. In the outdoors, moulds play a part in nature by breaking down dead organic matter such as fallen leaves and dead trees. Indoors, however, mould growth should be avoided.


Moulds emit tiny spores to reproduce. The spores are invisible to the naked eye and waft through the indoor and outdoor air continually. When mould spores land on a damp spot indoors, they begin growing by digesting whatever they are resting on in order to survive. There are moulds that can grow on wood, paper, carpet, and foods. When excessive moisture or water accumulates indoors, mould growth will often occur, particularly if the moisture problem remains undiscovered or un-addressed. There is no practical way to eliminate all moulds and mould spores in the indoor environment; the way to control indoor mould growth is to control moisture.

Ten things you should know about mould:

  1. Potential health effects and symptoms associated with mould exposures include allergic reactions, asthma, and other respiratory ailments.
  2. There is no practical way to eliminate all mould and mould spores in the indoor environment; the way to control indoor mould growth is to control moisture.
  3. If mould is a problem in your home or building, you must clean up the mould and eliminate sources of moisture.
  4. Fix the source of the water problem to prevent mould growth.
  5. Reduce indoor humidity (to 30-60 percent) to decrease mould growth by:
  6. -venting bathrooms, dryers, and other moisture-generating sources to the outside, using air conditioners and de-humidifiers;increasing ventilation; and Using exhaust fans whenever cooking, dishwashing, and cleaning. Clean and dry any damp or wet building materials and furnishings within 24-48 hours to prevent mould growth. Clean mould off hard surfaces with water and detergent, and dry completely.
  7. Absorbent materials that are mouldy, such as ceiling tiles, may need to be replaced.
  8. Prevent condensation: Reduce the potential for condensation on cold surfaces (i.e., windows, piping, exterior walls, roof, or floors) by adding insulation.
  9. In areas where there is likely to be a perpetual moisture problem, do not install carpeting. This includes areas by drinking fountains, classroom sinks, on concrete floors, or other areas with leaks or frequent condensation.
  10. Moulds can be found almost anywhere; they can grow on virtually any substance – including wood, paper, carpet, and foods – providing moisture is present.

Can mould cause health problems?

Moulds have the potential to cause health problems. They produce allergens (substances that can cause allergic reactions), irritants, and in some cases, potentially toxic substances (mycotoxins). Inhaling or touching mould or mould spores may cause allergic reactions in sensitive individuals. Allergic responses include hay fever-type symptoms, such as sneezing, runny nose, red eyes, and skin rash (dermatitis).

Allergic reactions to mould are common, and can be immediate or delayed. Moulds can also cause asthma attacks in people with asthma who are allergic to mould. In addition, exposure can irritate the eyes, skin, nose, throat, and lungs of both mould-allergic and non-allergic people. Symptoms other than the allergic and irritant types are not commonly reported as a result of inhaling mould.

For more detailed information consult a health professional or your local health department.

How do I get rid of mould?

It is impossible to get rid of all mould and spores indoors; some mould spores will be found floating through the air and in house dust. The mould spores will not grow if moisture is not present. Indoor mould growth can and should be prevented by controlling moisture indoors. If there is mould growth in your home, you must both clean up the mould and fix the moisture problem that’s causing the mould build-up. If the moisture problem is left to fester then the mould is likely to come back, despite all your hard work to clean it up.

This article was contributed to the Mose Report by mould specialist Richard Masterton.