Mould is the kind of thing that creeps up on you – it's not top of mind every day, unless you're a serious asthmatic, and it grows so fast that before you know it every nook and cranny is filled with the stuff. Keeping up a regular mould prevention scheme is a far easier way to go than trying to get on top of it once you have it.

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The key to preventing household mould is reducing moisture where possible, rather than using expensive mould removal products that may do more harm than good.

DIY mould removal

Professional mould removal

Mould cleaners

What causes mould?

How to prevent mould

Before you start

When you discover you're playing host to a mould colony, the clean-up process is labour intensive but relatively simple.

Before getting started sort the mouldy items into categories of non-porous, semi-porous and super-porous. 

If the mould is on something that is super-porous, like a textile, clothing or furniture, there's a good chance it can't be completely removed. Most moulds stain quite badly and also eat into surfaces; if they've grown on fabrics these may be permanently damaged and may need to be thrown out. Non-porous surfaces such as hard plastics should be relatively easier to clean. Semi-porous surfaces will be variable.

Carpets can be particularly problematic for anyone with a mould problem. You'll need to replace carpet if it's gotten wet. Don't fall into the trap of just letting carpet dry out if there's been water damage, as mould spores will be left behind, buried in the carpet fibres.

Anything that's super porous, like wicker baskets, textiles, paper and cardboard, or carpet, needs to be chucked away – don't even bother with these surfaces.

How to remove mould

  • The first step is to vacuum up the mould, but only if your vacuum is equipped with a good HEPA filter, otherwise you could be making the problem worse by spreading it around.
  • The second step is to remove the remaining mould. Our experts recommend using diluted vinegar (which causes mould to overeat and die) to clear surfaces of mould in the home.

How to use the diluted vinegar solution

  • Pour a concentration of 80% vinegar to 20% water into three buckets.
  • Grab a microfibre cloth, dip it into the first bucket, then use it for cleaning a patch of mould.
  • The same microfibre cloth should then be rinsed in the second bucket, then rinsed again in the third to ensure cross-contamination doesn't occur.
  • Microfibre cloths, which reach deep into tiny crevices and have a slight electric charge, can be bought cheaply and washed on a hot cycle in the washing machine with vinegar up to 100 times.
  • Using vinegar may leave streaks on surfaces, so further clean-up of those areas may be required for cosmetic purposes. In this instance, bleach can be used to remove discolouration.

Professional mould removal

In most cases, mould can be cleaned up without professional help. However, if mould covers a large area of your home – experts say a rough guide is one metre square – and is dense, or if householders are asthmatic, it's best to call in the experts.

Moulds can give off toxic spores and vapours, and if there's a lot of mould it can be dangerous – possibly resulting in hypersensitivity or allergic reactions, and asthma and flu-like symptoms. Areas that have flooded or have had prolonged mould build-up should be cleaned by someone with appropriate equipment, including a HEPA filter vacuum cleaner and proper respirators.

The cost of professional help varies. An initial investigation can cost around $1500 for an expert to test the site and find the cause of the mould and write a plan for removal of mould. After that, it's a question of the extent of the problem.

Actual removal of mould can range from $2000 to $90,000, depending on the contamination level and size of the property. Mould removalists need to be certified, have the right equipment, get special training, maintain a high level of fitness and have the ability to sustain thermal stress. They're not just cleaners, so their hourly rate can be $80–110.

Mould cleaners

Although most commercially available mould killers use bleach as an active ingredient, we find they don't work effectively.

There's evidence that bleach can kill fungi, but the concentration of bleach in products marketed as 'mould killers', including Power Force Mould Away, Woolworths Mould Cleaner, Coles Ultra Mould Remover, Selleys Rapid Mould Killer and Exit Mould, is less than five percent. Bleach has a short shelf life and loses potency quickly, so the longer products sit on shelves, the lower their bleach concentration becomes.

A product that starts out with a concentration of about four per cent states on its packaging that by the end of its shelf life it may contain just 0.6% bleach, however experts we spoke to recommend a 10% bleach concentration for killing mould.

Even at a higher potency, while bleach can kill off surface growth and spores on non-porous surfaces, it will not penetrate porous materials, contrary to claims made by several products on the market. If the mould is growing on plaster or grout or wood it will kill mould on the surface, but not below it.

In addition, several experts told CHOICE that bleach can be a masking agent. Bleach takes the colour, or melanin, out of fungi, making it invisible. You can't see it anymore, so you think the bleach has done its job, when that's not necessarily the case. Strong bleach is also harmful to grout and tiles as it erodes and corrodes the surfaces, making them more porous, which in turn makes them more vulnerable to further fungi growth.

What causes mould?

Moisture is a vital element in the development of mould. There are several ways in which moisture can enter the home and create a mould problem.

A leaky roof, broken pipes, or water from a flood can be external causes of moisture in the house. Mould grows very quickly and becomes a problem in areas that have been flooded – Hurricane Katrina, the Brisbane floods and the Japanese tsunami all saw serious mould issues emerge very rapidly once the flood waters had subsided.

Moisture can also be created within the building itself: through the overcrowding of rooms (people breathing and sweating creates moisture), air drying of clothes indoors, appliances such as stoves, washing machines and dishwashers with no exhaust systems and poor temperature control, leading to condensation on windows and walls.

When it's 40 degrees outside and you set your thermostat to an icebox inside, if there's a gap in the window or you open the door then hot, moist air will enter the home and condense on interior surfaces. This also happens if it's very cold outside, but you inconsistently heat the inside of the house.

Mould needs organic matter – such as dust or dead skin cells – to thrive, so it's important to keep up with regular vacuuming and dusting.

How to prevent mould

Prevention is key when it comes to mould. Bathrooms are havens for the stuff! To keep it to a minimum, install a good exhaust fan and prevent moisture build-up on surfaces. Squeegee or towel-dry your tiles and floors immediately after showering, and make sure you clean up scum, which mould feeds on.

Once mould gets its grip on grout or silicone, getting rid of it is almost impossible. When mould grows, it develops hyphae, or roots, which grow into the grout or silicone. You can clean the surfaces of the grout or silicone, but not deep into it. In those cases you have to replace the silicone or re-grout your bathroom.

Building ventilation is vital in homes. Inadequate ventilation is one of the main reasons homes become vulnerable to mould growth. When the air stops moving, you can get a build-up of humidity and moisture in those areas.

Australians need to make informed heating and cooling choices to ensure mould doesn't develop. Several experts we consulted warned against the use of unflued gas heaters, which release moisture into the air, and can lead to problems – particularly because people trying to heat their home aren't exactly going to open the windows to let the air flow!

The health impacts of mould

While mould is particularly problematic for the young, elderly or sick – and, as we mentioned, those with asthma and allergies – it can also be harmful to pretty much anyone. An allergy to mould can develop as a result of exposure over an extended period of time and, according to health experts, about 50% of people who live in mouldy conditions will develop hay fever-like symptoms.

Health conditions are made worse by the presence of mould, which increases symptoms in several ways: you might develop a sensitivity to mould, which can irritate your airways and aggravate asthma. Sometimes moulds can infect the sinuses, growing within the nose for example, and requiring surgical removal. In rare, worst-case scenarios, moulds can invade the lungs, taking root inside the body and creating big problems.