Sydney has been ranked the mouldiest capital city in Australia, and winter is when the problem peaks. Cold air, closed windows, indoor drying and coastal humidity combine to create ideal conditions for mould to spread across walls, ceilings, bathrooms and wardrobes. This guide explains why winter is the worst season for mould in Sydney homes, what professional mould cleaning involves, and how to keep it from coming back.

Mould is not just a cosmetic problem. It releases spores that affect indoor air quality and can trigger respiratory irritation, allergies and asthma. In a humid coastal city like Sydney, ignoring early mould almost always leads to a larger, more expensive problem later.

Why does mould get worse in winter?

Most people assume mould is a summer issue, but in Sydney it is winter that drives the biggest spike in growth. The reasons are straightforward:

• Windows stay shut, so moist air has nowhere to escape
• Indoor clothes drying releases litres of water vapour into the air
• Cold surfaces like windows and external walls cause condensation
• Heaters create warm, damp pockets where mould thrives
• Sydney’s coastal humidity keeps indoor moisture levels high year round

Where mould appears first in Sydney homes

• Bathroom ceilings, grout and silicone seals
• Behind and beneath wardrobes against external walls
• Window frames, sills and reveals where condensation pools
• Behind furniture pushed hard against cold walls
• Laundries and any room used for indoor clothes drying
• Ceiling corners in poorly ventilated bedrooms

Wiping mould away with a cloth removes what you can see. It does not remove what has already taken hold beneath the surface, which is why mould so often returns within weeks.

What professional mould cleaning involves

There is an important difference between surface wiping and proper mould cleaning. A professional approach treats the cause, not just the appearance:

• Identifying the moisture source driving the growth
• Treating affected surfaces with appropriate antimicrobial products
• Cleaning grout, seals and porous surfaces thoroughly
• Addressing odours rather than masking them
• Advising on ventilation and prevention so it does not return

When to call a professional rather than DIY

• Mould keeps returning after you clean it
• It covers a large area or has spread across a ceiling
• There is a musty smell you cannot locate
• Anyone in the home has allergies, asthma or respiratory issues
• You are preparing a property for sale, lease or final inspection

How to stop mould coming back

• Run exhaust fans during and after every shower
• Dry clothes outside or in a well-ventilated space where possible
• Open windows for cross-ventilation on dry winter days
• Keep furniture slightly off external walls to allow airflow
• Use a dehumidifier in rooms prone to condensation
• Wipe window condensation before it feeds mould growth

If mould has already taken hold in your home, the sooner it is treated the cheaper and easier it is to resolve. A professional mould clean from Royal Glow targets the affected areas thoroughly and leaves your home fresher, healthier and easier to keep clear through the colder months.