A Guide To Mould In Rental Properties

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 providing the following conditions are present:

A relevant indoor humidity of 80% or higher.
Moisture, usually from condensation. Mould can develop in the absence of condensation, but its growth is accelerated by the presence of moisture.
A nutrient. Research shows that certain ingredients in most paints, household dust, and cooking fumes all provide excellent food for mould.

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.

Who is responsible to treat mould?

Black Mould (Aspergillus niger) is a fungus which releases spores which cause health or allergic reactions such as asthma and dermatitis in some people. It grows in moist places which lack ventilation.

The responsibility to treat the mould usually falls upon a landlord, sometimes on a tenant.  Consumer Affairs provides these illustrations and advice:

  • A tenant may have allowed mould to develop in a bathroom by not using ventilation fans. If so, the landlord may serve the tenant with a notice requiring them to fix the problem.
  • A defective window frame has allowed rainwater to leak into the property, causing mould to develop. If so, the tenant may serve a notice to repair and the landlord must deal with this as a non-urgent repair.
  • It will be an urgent repair if the tenant proves that the mould is dangerous and/or is causing a health issue. The proof required is an expert’s assessment report by an occupational hygienist or an environmental health professional or a local council inspector; and a medical report if the tenant has an existing health issue such as asthma.

Condensation and mould

The winter season brings with it condensation and mould growth problems in houses, units, townhouses and villa homes. Condensation and mould can occur in any type of home construction, including weatherboard, brick veneer, solid brick, masonry veneer and monocrete.

Condensation and its causes

Atmosphere heavily laden with water vapour is referred to as being of high humidity. When highly humidified air comes in contact with any cold surface such as a wall or ceiling, it chills and water vapour is extracted from the air, remaining as condensation on the cold surface.

High humidity has an accumulative effect on absorbent materials such as clothing hanging in the cupboard or bedclothes, making them damp. Condensation will also cause rust on metal surfaces such as spring wire mattresses.

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, this means installing extractors in bathrooms and laundries.

Ways of improving ventilation

  • Open windows and doors when weather permits to improve cross ventilation. Where window locks are provided, lock windows open at 10cm when not at home.
  • On cold nights, when the house or flat is closed against the cold, ventilation should be ensured during the day.
  • If the dwelling is closed during the day, windows and inside doors should be open at night, particularly in spaces where heaters are operating.
  • Room ventilators and exhaust fans should be kept clean. Normal house fluff can block or partly block wall or ceiling ventilators and exhaust fans and impede proper ventilation of the property.
  • Turn on exhaust fans, particularly when bathing, showering, cooking, doing laundry and drying clothes.

Warm moist air

Warm air will not cause condensation on a cold surface, but warm moist air will. Warm moist air can be created by:

  • kerosene room heaters
  • steam from cooking
  • washing dishes or clothes
  • clothes dryers that are not externally vented
  • steam from bathrooms
  • drying damp clothes inside

What can I do to reduce mould in the property?

  • Mould growth is retarded by the circulation of dry air. It follows that proper ventilation will prevent most mould growth.
  • Open doors and windows to allow air to circulate; particularly in the bathroom during cool weather.
  • Keep bathroom walls, showers, shower curtains, baths and basins as dry as possible – open the door to allow air to circulate through the room.
  • Clean your bathroom and property regularly. Wipe away moisture on windows and walls to keep them dry.
  • Allow sunlight into the property as much as possible, especially in the bathroom, laundry and kitchen.
  • Wash and dry damp clothes, and dry and air damp shoes outside as soon as possible. To prevent green fluffy mould on clothes and footwear, ensure that they are thoroughly dry before storage. Leave the wardrobe doors open where possible.
  • Remove fruit and vegetables from the plastic wrapping and refrigerate within 27 hours. Discard mould items. Keep fresh food in sealed containers or with use of cling film.
  • Evaporation trays in air conditioners, dehumidifiers and refrigerators should be cleaned frequently.
  • Do not run evaporative air condition systems with water during times of high humidity (over 65%). If the air is feeling humid, run the evaporative air conditioning system without water. Always ensure windows are open when running an evaporative air conditioning system.
  • Regularly clean carpets and rugs to prevent mould spores using a High-Efficiency Particulate Air (HEPA) filter vacuum cleaner.  Most new vacuum cleaners include HEPA filters.
  • If water leaks of spills occur indoors, it is important to clean and dry the area immediately or preferably within 24 – 48 hours to prevent mould from growing.
  • Ensure the property does not have any water leaks that are visible. Report any leak to the Managing Agent.

How do I remove mould from the property?

  • Personal protective equipment, including half-face disposable le respirators with P1 or P2 filters are available at hardware stores, and should be used to avoid possible mould spore inhalation when cleaning.
  • Take additional precautions to prevent mould spore release and transmission by using drop sheets and exclude persons not performing the work from the area that is being cleaned.
  • Remove mould by using a suitable mould remover, such as:
  • A solution of 3 parts vinegar with 2 parts water
  • A solution of 70% methylated spirits and 30% water
  • A solution of tea tree oil and water, or
  • Commercial products available from supermarkets
  • Ensure that you comply with the safety precautions provided by the manufacturer to protect your eyes and skin from the solution or mould remover.
  • Wipe clean the affected area using a microfiber cloth with the cleaning solution. Use a two bucket system – one bucket with the solution and the other with clean water. Do not put the dirty cloth back in the solution – wash in the clean water bucket first. This avoids cross contamination.
  • After cleaning the mould affected areas with the solution, wipe the surfaces with a damp cloth. Do not use the same cloth used with the solution.
  • Wipe all surfaces dry with a clean cloth.
  • It is important to use a different cloth with each process and dispose of them immediately, otherwise, the mould spores will be spread and mould will reappear in a short time.
  • Do not attempt to dry brush the area using a broom or brush as this can increase the spread of mould.

 Fast facts

  • It is the responsibility of the Tenant to notify the Agent or Lessor 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 Lessor’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 Lessor/Agent 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 Lessor would be liable for the repairs.


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If you have a property in Brisbane that you would like to consider engaging a new property management team for, please feel free to contact Paul Tooze directly on 0414 037 007 or the friendly team at All Properties Group (07) 3800 0988.
Otherwise, we hope you have enjoyed these insider tips.