Mould can appear in your home at any time of the year, and it can cause serious health problems along with adding a certain dinginess to your surroundings. 

But it's winter that you really have to watch out for, especially if you're living in a rental property with poor ventilation and spotty indoor heating.  

What causes mould? And what are your rights if you're a renter or an owner? 

How much does it cost to have mould professionally removed, and is it worth the money? 

Read on to find the answers. 

On this page:

• What causes mould?
• Tips for keeping your house mould-free
• Is the landlord or tenant responsible for mould?
• Tips for renters to avoid problems
• Does insurance cover mould?
• Professional mould removal

What causes mould?

Simply put, moisture causes mould.

"People have no idea how much a little water can do," says Dr Heike Neumeister-Kemp, chief mycologist (mould expert) from Mycolab.

A leaky roof, broken pipes, cracked roof tiles, windows left open while it's raining or a flood can cause moisture to enter your home. Or you could be creating the moisture within the home itself: through air-drying clothes indoors, running appliances without an exhaust, or by under- or over-heating your home in the winter or over-cooling it in the summer.

It's important to figure out what's causing your mould problem and to fix the underlying issue, otherwise it will continue to occur, regardless of how thoroughly you may think you've cleaned.

Is having mould in your house bad for you?

Moulds can give off toxic chemicals, called mycotoxins, and if there's a lot of mould these nasties can cause allergic reactions, asthma and flu-like symptoms. It's not something anyone should have to live with. 

Tips for keeping your house mould-free

• Keep the temperature in your home even. Try not to let one room get much warmer or colder than the next.
• In winter, have small heaters spread throughout your home rather than one large heater in the centre. See our article on the best heating options for renters. 
• Never use unflued gas heaters because they can release water vapour into the air.
• Always use the exhaust when you're showering or cooking and open windows when possible.
• Clean up mould as soon as you notice it. Don't let it settle in.
• Wipe up condensation on walls or windows whenever you notice it.
• Keep blinds and curtains open during the day.
• Tell your landlord as soon as you notice a problem and keep a record of any conversations you have over the phone.

Depending on how damp an area is, the severity of mould can vary, from small patches to major infestations.

Is the landlord or tenant responsible for mould?

Landlord's obligations

In Australia, landlords have a general obligation to ensure the homes they lease out are in a reasonable state of cleanliness and fit for habitation by the tenant. 

If mould is caused by a leak in the roof, a faulty pipe or gutters or other structural faults, your landlord is responsible for fixing it and remediating the damage.

Tenants' obligations

But mould is often not caused by structural issues. 

• Tenants may be contributing to or creating the problem themselves by failing to regularly air out and clean the house, allowing condensation to build up in the home, or getting the carpet wet.
• Tenants also have an obligation to inform landlords or their leasing agents if there's a problem with the property, for example a window that doesn't seal or a leaky pipe.
• If a tenant has caused the underlying problem that led to mould developing, or hasn't informed their landlord of an issue with the property, they could be held responsible for mould damage and may have to compensate their landlord.

There are still plenty of grey areas, according to Neumeister-Kemp, who often acts as an expert witness in court cases that deal with mould damage.

It's up to a judge to decide whether the mould is bad enough and whether the issue is with a building defect and therefore the owner is at fault

Dr Neike Neumeister-Kemp, chief mycologist at Mycolab

With no clear-cut responsibility laid out in law, landlords may not accept they're responsible for mould, forcing tenants to go through housing tribunals or the courts, which takes time and, in some cases, money.

"At the moment, it's up to a judge to decide whether the mould is bad enough and whether the issue is with a building defect and therefore the owner is at fault," Neumeister-Kemp says.

Tips for renters to avoid problems

Before you lease a property

If you notice issues such as windows that don't seal properly, leaky taps or broken gutters, make sure you get your landlord to commit to fixing the issues in writing before you sign the lease.

Take steps to check for mould before signing a lease, and commit the landlord or agent in writing to fixing any problems.

While you're leasing a property

If you're already leasing a property and a mould problem develops, try to figure out what's causing it. 

If it's a small amount of mould in the bathroom or kitchen, clean it up and air the rooms out well in future. 

But if there's a significant amount of mould, or you find a leak in the roof or walls, tell your landlord or real estate agent immediately and ask them to fix it. 

The longer you wait to tell them, the worse the problem will become – and you could well be held liable for any delay. 

Make sure you keep good records of your contact with the landlord or agent and take plenty of photos in case you need them for evidence later.

If you're not satisfied

If the landlord won't fix the issues or you're not satisfied with the repairs that have been done, you do have some options. 

You can seek to terminate your lease early. The landlord may not agree to your request, in which case you may need to go to a tenancy tribunal in your state or territory to resolve the dispute. 

If that's the case, make sure you bring as much evidence as possible, including your correspondence history with your landlord or agent, photos you've taken, and, if you have one, an environmental report on the mould in your home. 

You can get one from a mould remediation specialist, or in some cases, from your council.

Does insurance cover mould?

If you own your home and have a problem with mould, there's not much you can do to alleviate the cost of fixing it. 

Home and contents insurance tends not to cover mould damage, particularly when it's caused by lack of maintenance, such as blocked gutters or missing ceiling tiles. 

When mould is a secondary issue that arises as a result of water ingress from flooding, storm damage or burst pipes, you may be covered, according to Neumeister-Kemp. As always, you should read the terms and conditions of your insurance policy carefully.

If your mould problem is severe, you may have to call in a professional to get rid of it. Who pays depends on the source of the mould.

Professional mould removal

Surface mould, such as that found on bathroom tiles or on the surface of kitchen cabinets, can be cleaned up fairly easily without calling in outside help.

But if mould covers a large area of your home – according to the Australian Mould Guideline, which was co-authored Neumeister-Kemp, a rough guide is one metre square – and is dense, or if householders are asthmatic or allergic to mould, it's best to call in the experts.

Once mould sets into porous materials, it can be easier to replace them entirely than to treat them

Professional mould cleaners should be certified, have the right equipment and special training.

Neumeister-Kemp says badly affected homes may have mould behind walls, in and behind gyprock, in ceiling cavities and under carpets and floorboard. Once it sets into porous materials, it can be easier to replace them entirely than to treat them.

Stock images: Getty, unless otherwise stated.

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