How to clean mould safely, and why not use bleach

For a very small patch of mould on a hard surface, use an appropriate mould and mildew cleaning product, follow its instructions and let the surface dry completely. Wear a mask, gloves and goggles; shut the door and keep the window open while you work. Government guidance prefers mould and mildew products to bleach for health and safety reasons. Cleaning the patch matters, but finding and fixing the moisture behind it matters just as much, or the mould can return.

Why the guidance says to choose a mould cleaner over bleach

The government guidance is direct: mould and mildew products should be used in preference to bleach for health and safety reasons. RICS also recommends mould and mildew cleaning products for hard surfaces and describes them as more effective and safer than bleach. That is the useful comparison here. These sources do not give a method for using bleach on mould, so there is no reason to build a cleaning routine around it.

The cleaner deals with what is visible on the surface. It does not repair a leaking gutter, improve faulty ventilation or explain why a wall is wet. A fresh-looking wall can still have the same moisture problem behind the mould. If the source remains, simply removing the surface growth will not prevent it reappearing. Treat cleaning as an immediate practical step, then investigate the damp rather than assuming the job is finished.

How to clean a very small patch safely

Government guidance says most tenants could reasonably be expected to remove condensation and very small amounts of mould with an appropriate mould and mildew cleaner. That is a narrow recommendation. A larger area belongs with a qualified professional, and a mouldy carpet or soft furnishing may need specialist cleaning or may be impossible to clean completely. Do not treat every material as though it were a wipe-clean wall.

• Before cleaning, photograph the affected area. The record may help identify where the moisture is coming from and plan what needs fixing.
• Wear a mask, gloves and goggles. Shut doors to limit the spread of mould spores to other rooms, and leave windows open during and after cleaning.
• Use an appropriate mould and mildew product on the hard surface, follow the product guidance and allow the surface to dry completely.
• Afterwards, wash or carefully dispose of protective equipment and clothing. Wash or dispose of the cloth or sponge used for cleaning, and bag and dispose of any removed material safely.

These precautions apply even when the patch looks small: the government guidance says the person removing mould should wear protective equipment regardless of the extent of the mould. Keep cleaning products stored away from children, as RICS advises. If mould covers a substantial part of a wall or ceiling, arrange for qualified professionals to deal with it rather than trying to scale up the same household clean.

Find out why the surface became damp

Start by looking for where water is entering or collecting. Condensation forms when moisture in indoor air meets cooler parts of the building; it can show around windows or on walls. Water can also come through defects in roofs, walls, windows or floors, or from a plumbing leak. More than one source can be involved. The pattern of the mould is a clue, but it is not a reliable diagnosis by itself.

Check for obvious defects such as damaged or blocked gutters and downpipes, broken seals around windows, roof damage, plumbing leaks and extractors that are blocked, broken or switched off. Note whether condensation appears on cold surfaces and whether a musty smell persists where no mould is visible. The government guidance says hidden mould may sit behind wallpaper or furniture or beneath carpets; take care before disturbing these areas, because doing so can release spores. If the cause is uncertain, get someone suitably qualified to investigate rather than guessing from the stain.

Keep ventilation working where moisture is produced. RICS advises using extractor fans while cooking, bathing or showering, checking that they work well, and wiping condensation from cooler places such as windows and bathroom tiles. Those everyday steps can help manage moisture, but they cannot replace a repair to a building defect or a proper assessment of a recurring damp patch. If you rent, report mould and maintenance concerns to your landlord or managing agent promptly. Landlords should investigate, deal with the underlying cause and explain the work to the tenant.

Cleaning mould in a Yorkshire or Lancashire stone terrace

In a stone terrace or an older home with solid walls, resist the urge to choose a damp-proofing treatment just because mould has appeared. RICS cautions that such measures may be inappropriate in older solid-wall buildings and can make damp worse. Look first for the moisture source and for routine maintenance issues, such as gutters, pointing, render, window seals and indoor ventilation. A cold external wall may collect condensation, while a defect can also let water in; either possibility needs checking in the particular home.

When the picture is complicated or mould keeps returning, ask an independent, suitably experienced building surveyor with expertise in moisture and building pathology to identify the cause. RICS advises checking the surveyor's experience rather than relying on a professional title alone. A diagnosis should guide any repairs to the building; surface cleaning on its own cannot tell you which repair is needed.

This page gives general information, not legal or medical advice. For your own situation, use the organisations listed under "Where this comes from" at the foot of the page.