Since the inquest into the death of two-year-old Awaab Ishak, the threat of black mould in UK homes has been much discussed in the media. While the tragedy occurred in a flat owned by a registered social landlord, private rented sector housing providers are also looking into how they can better protect their residents.
What can letting agents and landlords do to prevent black mould – or get rid of it when it occurs?
Identifying and treating black mould
Black mould is a common name for several different types of dark-coloured microscopic fungus. It grows on damp surfaces, either because of condensation forming or water leaking into the property. Some of the biggest trouble spots are around windows, in basements and especially in bathrooms.
Black mould exposure can cause sneezing, skin rashes and asthma attacks. Babies, children and older people are at higher risk from this, as are people with weakened immune systems or respiratory issues.
Commercial bleach-based mould sprays are available in supermarkets, and white vinegar will also kill mould and mould spores – even on porous surfaces like paint. But mould can easily grow in places that are difficult to see or reach, like behind radiators or under carpets.
Even more crucially, if the damp conditions that allow black mould to grow aren’t taken care of, no amount of bleach will prevent it from growing back.
Prevention is better
In light of this ongoing threat, renovating properties to stay warm and dry is the best means to prevent growth.
The English Housing Survey 2020 found that just under 10% of privately rented homes – around 400,000 – had damp issues serious enough to be noted on a Housing Health and Safety Rating System survey, with more suffering from lower levels of damp.
Replacing single-glazed windows with double or triple glazing will cut condensation while also helping rented properties adapt to rising EPC requirements. Insulating the property has the additional benefit of helping to keep energy bills down.
But insulation can also make mould problems worse, especially in older buildings. By reducing airflow, it can trap moist air indoors, leading to more condensation and more mould.
Choosing double-glazed windows with trickle vents and ensuring that air bricks are unobstructed will help provide passive ventilation. For a more active solution, installing extractor fans in high-moisture areas like bathrooms can actively keep humidity levels down – especially if they run automatically instead of relying on tenants to turn them on and off. Picking a model with a timer or humidity sensor ensures that the fan will be on at the times it is most needed.
Plug-in dehumidifiers can also be extremely effective but rely on the tenant to actually use them despite the fairly high running cost. Landlords who include bills in the rent, for example when renting out a House of Multiple Occupation, may be in a better position to ask tenants to use a dehumidifier – so long as they can factor the extra electricity into how much rent they charge.
If landlords are prepared to fully renovate a property, anti-mould paint or emulsion will help reduce the chance of mould forming while providing an anti-damp base coat. Extra air bricks can also be installed in problem areas. However, mechanical ventilation with heat recovery (MHVR) is the gold standard for highly insulated homes with little airflow. The level of airtightness needed to bring a home up to EPC C as of 2025 may make this kind of system necessary in many cases.
Supporting lifestyle fixes
In a perfect world, every tenant would keep the thermostat at 20 degrees, dry their laundry outside, open the windows regularly and run a dehumidifier to keep damp at bay – but that’s not the world we live in. The running cost of heating and dehumidification is a tough sell with utility prices rising, while tenants may not know what an air brick is or why putting furniture in front of one is a bad idea. Tenants may also put off reporting damp issues for fear – justified or not – of retaliatory eviction.
Adding a few friendly words of advice on damp prevention to the start-of-tenancy welcome pack, along with legal must-haves like the How to Rent Guide, might seem patronising, but it can save both tenants and landlords a headache later.
Asking tenants to report issues early also gives landlords and agents an opportunity to see if the problem is damp ingress or tenant behaviour, and to give ventilation advice or arrange maintenance as necessary. Using instant online communication systems like PayProp’s maintenance reporting feature allows for transparent three-way communication between tenants, landlords and agents.
Finally, regular inspections are a chance to check mould hotspots for signs of growth and take action when it is identified, as well as make sure that air bricks are unobstructed and extractor fans are active.