Finding mould in your loft can be pretty alarming, especially if this is a space you rely on to store precious belongings or items such as Christmas decorations or out of season clothing – things you really don't want to pull out and find covered in the stuff.
While there are plenty of mould removal tricks you can employ to deal with the issue in the short term, it is really important to discover the root of the problem if you want to ensure it doesn't become a recurring issue that could, eventually, lead to serious damage, not just to the items you keep up there, but also to the structure of your home.
The good news is that there are steps you can take to resolve mould in the loft and, with the help of some top experts in the field, we're here to to explain exactly what they are.
Why does mould appear in lofts?
It might be reassuring to know that mould in lofts is actually quite common, caused by a number of things, although there tends to be one main culprit: poor loft ventilation.
"In most cases, warm, humid air from the living areas below rises and enters the loft through gaps in the ceiling, around the light fittings or through poorly sealed hatches" explains HVAC and ventilation expert David Miloshev from Fantastic Services. "When that warm air meets the colder surfaces of the roof timbers or underlay, the moisture condenses, creating the perfect environment for mould spores to thrive.
"Insufficient ventilation is a key factor," continues David. "If the loft lacks adequate air movement from soffit, eaves or ridge vents, the moisture becomes trapped and remains in contact with those cold surfaces for long periods."
"Mould in lofts is nearly always caused by trapped moisture and poor ventilation," agrees Michael Zohouri, founder of Pyramid Eco. "Warm, moist air from bathrooms and kitchens rises into the loft. If there’s nowhere for that air to escape, it condenses on cold surfaces such as roof timbers and insulation. It's much more noticeable in the winter because the loft is cold and the temperature difference increases condensation. It creates the perfect environment for mould to grow."
David Miloshev has worked with Fantastic Services as an appliance technician and certified electrician for more than five years
Michael Zohouri is the founder of Pyramid Eco with over a decade of retrofit experience. He specialises in tackling mould, damp and ventilation issues, alongside sustainable upgrades such as heat pump installations. His focus is on creating healthier homes that improve air quality and energy efficiency.
Why do some homes suffer from mould in the loft more than others?
Not all homeowners experience the problem of mould in their loft. This is not just down to them having better home ventilation measures in place. In some cases, the way in which people live in their homes can exacerbate the problem.
"In some homes, the issue is made worse by bathroom extractor fans or tumble dryer vents discharging moist air directly into the loft instead of outside," reveals David Miloshev. "Poor insulation, or insulation that’s been pushed right up to the eaves can also restrict airflow and exacerbate the problem."
How can you prevent mould in the loft?
Thankfully there are preventative measures you can take to put a stop to mould forming in your loft.
"Preventing mould in loft spaces requires controlling the moisture levels and ensuring proper ventilation throughout the area," explains David Miloshev. "The first step is to stop warm, humid air from the living spaces below from entering the loft. This can be achieved by sealing any gaps around the light fittings, ceiling hatches and any service penetrations, and ensuring loft and roof insulation is correctly installed without blocking airflow from soffit or eaves vents.
"Ventilation itself is critical," continues David. "Soffit vents, ridge vents or additional roof vents should allow a continuous flow of air that carries moisture out of the loft. Any appliances that produce moisture, such as bathroom extractor fans or tumble dryers, should be correctly ducted to the outside instead of discharging into the loft.
"It’s also important to maintain a temperature in the loft that minimises condensation," adds David. "This can be supported by ensuring insulation is adequate but not obstructing airflow. Finally, regular inspections are also useful. Checking for blocked vents, signs of leaks or condensation buildup for early intervention before mould can establish itself."
What should you do if you find mould in your loft?
If you have noticed any mould in your loft, what should you first steps be?
"First you need to stop the source of moisture," says Michael Zohouri. "That might be a ventilation issue, a leaking roof tile, or an extractor fan that’s not vented properly. Once the area is dry and the airflow is working as it should, you can treat the mould."
"If you find mould in a loft, the first step is to identify and address the underlying cause instead of just removing the visible growth," picks up David Miloshev. "Start by inspecting the space for sources of moisture, such as roof leaks, blocked or inadequate ventilation or warm, humid air escaping from the rooms below. Once the source is identified, it should be corrected. Repair any leaks, unblock or install proper ventilation and make sure to look into how to insulate a loft correctly to allow airflow.
How do you remove mould in a loft?
Of course even once you have found the cause of your mould and put measures in place to prevent it from returning, you still need investigate how to remove mould from walls and the space in general once it has taken up residence.
"If the mould is only in a small area and caught early, you can clean it yourself," says Michael Zohouri. "White vinegar works well as a natural mould remover. Spray it directly onto the surface, leave it for an hour, then scrub with a cloth and wipe the area dry. There are also specialist mould treatments available from DIY shops if you prefer a ready-made solution. Always wear gloves and a mask while cleaning, and avoid dry brushing as that can release mould spores into the air."
"Large or persistent infestations will require professional remediation, particularly if the mould has penetrated the insulation or roof timbers," advises David Miloshev. "After cleaning, monitor the loft over time to make sure that moisture levels are controlled and the ventilation is functioning correctly. Failure to fix the source of the problem will almost always result in the mould returning."
Shop mould removal essentials
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FAQs
Is mould in the loft dangerous?
Mould can pose a serious health risk if left untreated in a home, particularly if any of the residents suffer from skin or respiratory problems. But how about when it is up in the loft?
"Mould in lofts can be hazardous, although the level of risk depends on the type of mould, the extent of the infestation and the exposure of occupants," explains David Miloshev. "Many loft moulds release spores into the air, which can enter the living spaces through gaps or ventilation, potentially causing allergic reactions, respiratory irritation or exacerbating conditions such as asthma. Prolonged exposure to certain types of mould, particularly black mould, can be more serious and can lead to persistent respiratory issues, skin irritation or other health problems.
"The affected structural materials themselves are usually not immediately in danger, but mould can weaken timber over time if left untreated, especially if it’s combined with ongoing moisture issues," continues David. "The primary concern is controlling the moisture and preventing the spores from spreading into the home. Anyone cleaning mould should take precautions with protective equipment to minimise inhalation or contact."
If you have found mould in your loft you might be wondering where else in your home it might be lurking. Our guide on hidden mould hotspots is a must-read to ensure you're not missing anything.
