Mould: Cause, Prevention & Removal

A lot of homes can suffer from some degree of mould during the winter months and it could range anywhere from a small patch on a wall somewhere or to a serious mould growth across walls and ceilings and is usually a result of a combination of high moisture levels and inadequate ventilation.

Here are some tips from our Property Management Team, who deal with this issue regularly, about the cause, prevention and removal of mould from your home. Prevention is best but if you already have an outbreak of mould there are some things you can do to get rid of it.

Sometimes, mould can be caused by a building fault such as a water leak from damaged gutters or roof causing a higher moisture content and encouraging the growth of mould. If you suspect that the mould is from a structural failure you should let your property manager know as soon as possible so that it can be attended to.

What is Mould?

Mould is a form of fungus and is spread primarily by airborne spores that will develop and grow on almost any surface.

One of the main causes of mould is condensation from high relative humidity in the air or too much water vapour or steam being generated through cooking, washing, bathing, showering and clothes drying which is allowed to travel throughout the house. The only way to stop mould generating from these causes is to VENTILATE the property.

Sooty mould, the most common type, leaves surfaces with a brown or black stain and usually occurs on the walls and ceilings of bathrooms, bedrooms and in cupboards. Untreated, this mould will spread to other rooms in the house.

Green furry mould grows on organic or organic-bearing surfaces, such as shoes or clothes.

Example of Sooty Mould

What is Condensation?

Condensation occurs where moist warm air comes into contact with colder drier air, or a surface, which is at a lower temperature.

Condensation is generally noticeable where it forms on non-absorbent surfaces, but it can form on any surface and may not be noticed until mould growth or rotting of material occurs.

The moisture in the air comes from a number of sources within the house. Water vapour is produced in relatively large quantities from normal day to day activities such as breathing, cooking, baths and showers and washing clothes.

In certain areas of a house (such as bathrooms and kitchens) the warm air contains a lot of moisture, if the air then spreads to cooler parts of the house it condenses on any colder surface.

How to prevent condensation

Condensation cannot occur if humid moist air is removed and replaced by dry air. This can be achieved very simply through better ventilation of dwellings.

Ways of improving ventilation

  • Use a Dehumidifier which is designed to keep a room’s humidity levels in check, so the air is more comfortable and you notice fewer physical signs of damp air. Dehumidifiers draw excess moisture from the air – helping to combat condensation, mould and damp on walls, windows and peeling paint and wallpaper.


  • Increase circulation of fresh air in your home by opening windows and doors and leave them open for the whole day (if possible). If security is an issue when leaving windows and sliding doors slightly ajar to ventilate, then please contact your managing agent and request window and door locks be fitted.


  • Dry clothes out of doors or in a cool area of the premises – this latter suggestion may sound strange, it will take longer but less moisture will be held in the air at any one time. While drying clothes indoors, ventilate the room to the outside. Dryers should have external air extraction. When people come in with wet coats, they should be hung outside to dry. Ensure shoes and clothes are dry before putting them away.


  • Let the sun into the home by leaving blinds and curtains open


  • Wipe away any visible moisture on walls or windows, keep the inside as dry as possible


  • Don’t have too many indoor plants.


  • When heating the home leave the blinds and curtains open as well as opening the windows at some stage so air can flow through.


  • When taking a hot shower or bath ensure the exhaust fan is on, when finished open the bathroom window and allow the moisture to escape outside. If you feel your exhaust fans are not working property contact your managing agent and request that these be checked and repaired or replaced if necessary.


  • When cooking ensure you turn on the range hood fan or exhaust fan and open the window. If you feel your range hood fan is not working property contact your managing agent and request that these be checked and repaired or replaced if necessary.


  • Do not use a Vaporiser unless you are using a de-humidifier at the same time. Vaporisers create moist air which in turn creates mould. If you us the de-humidifier in conjunction with the vaporiser the moist air will be removed from the room avoiding mould.


The earlier you remove mould from walls and ceilings the easier it is to keep under control. It is harder to remove mould once it takes hold. Wash the mould with white vinegar and leave it for at least one week. This kills the mould spores, rather than just removing it from the surface allowing it to re-appear later.

After this, wash the area with either exit mould or bleach based product suitable for the surface being washed. If using bleach, mix it with three parts water.

CAUTION– When cleaning mould & using chemicals ensure skin & eyes are protected and windows are open to allow ventilation. Ensure all care is taken when cleaning mould, if you have allergies or medical conditions seek further advice from your doctor.



  • It is the responsibility of the Tenant to notify the Property Manager of any serious/extensive mould problem.
  • If the mould is a result of an issue in the premises, such as a roof leak, it is generally the Landlord’s responsibility to clean the mould and make any repairs necessary to maintain the property in good repair.
  • If the Tenant caused the mould, they are responsible for its removal and may have to pay to repair any damage caused.
  • At the first sign of any problem, the Property Manager and Tenant should discuss the issue.

An example of who’s responsible: If the Tenant continually allowed steam to build up in the bathroom without proper ventilation and /or regular cleaning, resulting in mould, then the tenant may be liable. If the mould is a result of a structural issue, e.g. a roof leak, then the Landlord would be liable for the repair.

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Mould: Cause, Prevention & Removal