Condensation, moisture damage and mould

Condensation, water ingress and moisture damage have been increasingly observed in Victorian residential buildings.

Water damage routinely tops the list of defects encountered in buildings and in complaints and disputes to us and claims to the Victorian Managed Insurance Agency (VMIA).

Water ingress is when water makes its way into a building. It can occur for various reasons and in different ways, including through condensation. This can lead to immediate damage or slow deterioration of building elements. If left untreated, it may lead to severe structural damage and expensive repairs, or health issues from mould growth.

What is condensation?

Condensation occurs when warm, moist air comes into contact with a cold surface and condenses into water droplets.

Air has the capacity for holding water vapour otherwise known as humidity. As moisture-laden air gets close to cold surfaces – such as walls, floors, sub-floor areas, roof spaces – it starts to get cooled and so the relative humidity increases; the greater it is cooled the higher the relative humidity. When moisture-laden air touches a cold surface, the temperature of the air drops below the dew point temperature and water droplets form.

What are the causes of condensation and mould?

Condensation in your home can be caused by:

• cooking and boiling a kettle
• cleaning
• bathing
• drying clothes indoors
• poor ventilation
• inadequate heating.

Where there is a lot of condensation it can cause problems with damp and mould.

Mould grows best in damp and poorly ventilated areas.

How do I know if I have a condensation problem or risk mould growth?

Common signs of a condensation problem or risk of mould in your home include musty or damp smells as well as visual signs, including:

• Condensation on your windows and sills

• Peeling or blistering of paint on your walls 

• Damp patches or discoloration on walls and ceilings

• Mould growth in bathrooms, kitchen or on furniture

What should I do to protect my property and health?

Homeowners, tenants, and property owners should regularly check for signs of condensation or water damage inside the home. If not checked or maintained regularly, the consequences potentially pose serious safety and health risks.

Generally, the longer condensation or water ingress is left untreated the greater the risk of mould growth, property damage and rectification costs.

There are simple steps you can take to protect your property and your health (and the health of those living with you).

Reduce water ingress or moisture:

• Wipe up excess water caused by condensation such as on windows and on shower glazing.
• Avoid drying clothes over heaters or in non-ventilated rooms as this adds to the indoor moisture. Where possible, dry clothes outside.
• Ensure gutters are cleared and maintained regularly to avoid roof leaks.
• Keep an eye out for water leaks through windows, doorframes or through the roof.
• Hire a licenced plumber to fix any leaky plumbing or blocked drainage pipes.
• Hire a registered builder to fix building faults to prevent water ingress into the home.

Improve ventilation:

• Air the home regularly by opening windows and doors on warmer days. Keep the home well-ventilated.
• Use exhaust fans, or open windows in the bathroom and kitchen when showering, cooking or using the dishwasher.
• Use reverse cycle air conditioning and or mechanical dehumidification if available.
• Maintain heating, ventilation and cooling systems (this includes regular servicing) according to the manufacturer’s instructions.
• Increase air circulation around furniture by moving the furniture away from the walls.
• Try not to stack boxes or things against the outside walls especially walls that don’t get much sun.

Helpful information

• Information on the health impacts of dampness and mould in the home is available in an infographic prepared by the Healthy Housing Centre for Research Excellence.
• Information on what mould looks like, what causes it to grow indoors and actions that can be taken to reduce it is available from the Better Health Channel.
• Information on mould removal at home is available from the Better Health Channel.
• Information on mould in rental properties and rights of tenants is available on Consumer Affairs Victoria’s website.