Mould in your loft? Here’s what to do

Mould doesn’t need a lot to grow, and it can occur in many rooms of your home, including kitchens, bedrooms, bathrooms and, of course, lofts. As long as there is water, food and oxygen present, then mould has all the conditions it requires to survive and thrive.

Lofts and attics can be the perfect breeding ground for mould, as poorly insulated lofts create the cold surfaces and highly-humid conditions that mould needs to grow. When the surface temperature reaches a critical saturation point, the humidity will condensate on the surface. This is known as the “dew point”. This is why protecting your attic from water and condensation is crucial.

Condensation in your loft can occur for various reasons. If you believe that your mould issue is developing because of condensation on your loft windows, check out our article: ‘how to stop condensation on windows’.

What causes mould growth in a loft?

So what actually causes mould to grow?

As previously mentioned, food, water and oxygen are the main necessities mould needs to grow, and poorly insulated attics often result in all three!

When entering your attic, does it feel slightly stuffy or warm? Unless you have built a warm attic*, this should not be the case.

*A room in your home that is occupiable as insulation is directly under the roof

When attics are built, the use of ventilation or ridge vents is imperative to keeping the room cool and mould-free. If these vents are blocked in any way, the circulation of cool air stops, creating a more humid environment. As the loft cools, so does water in the air, creating condensation.

Where can mould grow in a loft?

Mould has the possibility of growing on anything that contains organic matter.

Organic matter can be found in anything from typical food items such as bread and sugary drinks to things like wood and dust. Annoyingly, objects such as mineral insulation and wooden joists contain organic matter, which gives mould the opportunity to grow in lofts and attics.

Mould on insulation foam

Insulation foam that contains mineral wool is one of the best environments for mould growth.


If your loft suffers from water retention or condensation, then you will eventually suffer from mould in your attic’s insulation. When the mineral wool comes into contact with water, typically through condensation, the moulding process will begin and the growth speed can be alarming.


Unless caught quickly, you may require the help of a mould removal specialist to ensure that all contaminated foam is removed. If some mould remains, the possibility of further spread continues.


Mould spores are another reason you may want to bring in a mould removal specialist. When in the presence of mould spores, you may experience shortness of breath, eye irritation as well as allergic reactions. Black mould is particularly harmful.

Mould growth on wood in the loft

As stated previously, mould growth can occur on any surface or object that contains organic matter of any kind, and this includes the wood in your loft.

The first thing you will have to do is try and figure out what type of mould has taken over your wood. If only the surface has been contaminated, then you’re in luck. A professional mould removal specialist will be able to remove the surface-level mould and then sterilise the surrounding area.

If the mould contamination has gone deeper, then it is more serious as this can affect the structural integrity of your roof. Visible mould and fungus can be removed, but further repairs will be required. If you believe you are suffering from this type of mould, we would suggest getting in contact with your local specialist as soon as possible.

What should I do if I find mould in my loft?

If you spot mould in your loft, we would advise you to get in touch with your local mould removal specialists as soon as you can. If the right conditions for mould growth remain, the problem may continue to get worse the longer you leave it.

How do I stop mould growth in my loft?

Here are a few things you can do to minimise the risk of mould growth in your attic:

Ventilating your loft

Ensuring that your loft or attic has efficient ventilation will keep the humidity in the air of your attic down and reduce the chance of condensation or moisture forming. Blockages can occur when vents are unintentionally covered with rugs or quilts, so be sure to check any ventilation isn’t blocked.


Adding a skylight window is a great idea for improving ventilation. If you’re looking to ventilate your inhabited room (such as an attic bedroom), try an openable roof window.


Without the correct amount of insulation in your loft, warm, moist air could enter, creating a humid environment. As the air cools, it condenses and will form condensation, increasing the chances of mould growth. To avoid this issue, make sure that your attic or loft has the optimal amount of insulation and does not have any uninsulated areas.

It will also keep your home warmer and help reduce your energy bills.

Read our extensive articles on how to insulate an attic room as well as how to improve home insulation.

Roof Leaks

Another issue you may come across is roof leaks. Obviously, if your roof has a leak, then water can enter your loft.

If the temperature of your loft then fluctuates, mould will have everything it needs to start growing. To avoid this issue, be sure to check your attic every few months for potential leaks or holes. If found, we would advise getting in contact with your local roofer.

Read our guide on roof window leaks.

If you’ve spotted mould in your loft, call a mould specialist to remove it, then think about installing a roof window and improving insulation to prevent it from coming back.

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