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Preventing mould in school buildings

More than simply a cosmetic issue, mould can lead to poor health and structural damage. Happily, Richard Walker has all you need to know to prevent it

Posted by Julian Owen | April 19, 2019 | Security & safety

Mould is something no facilities manager or school caretaker wants to see in their building. It is not only a potential health issue, but can indicate a wider damp problem. Issues with damp and condensation often lead to side-effects - such as unpleasant odours, dark stains on walls and surface damage to paintwork - which are all characteristics of mould growth. These signs mean there is possible structural damage to the premises. 

There is also potential health risk associated with mould growth. According to the NHS, it can produce allergens, irritants and toxic substances. Inhaling or touching mould spores may cause an allergic reaction such as sneezing, a runny nose, red eyes, skin rashes, or even an asthma attack. While cases like this are rare, those responsible for the upkeep of a building should be vigilant. 

In this piece, I’ll explore how facilities managers and caretakers can control moisture in the school environment by looking at the root causes and, in turn, limit the potential for mould growth and the others effects of damp. 


This is formed when moist, humid air comes into contact with a cold surface. Everyday activities such as cooking, boiling the staffroom kettle, or even drying wet tea towels on radiators, can contribute to condensation forming. A large number of people in a small room during class can also cause fluctuations in humidity, resulting in condensation. It is most commonly seen between the months of October and April - when windows are typically kept closed, to preserve heat - and there is a big difference in temperature between the interior and exterior of the building. 

Ventilation is the key to preventing condensation from forming. If the school has double glazing, then keep the trickle vents open and thus ensure there is moderate ventilation. When cooking in the canteen, try to ensure doors are closed and an extractor fan is used, so the water vapour does not spread into other rooms. 

Heating also plays a vital role. When using central heating, warm the whole premises on a low heat, rather than leaving some rooms cooler and susceptible to condensation. 

The cost of repairing a damp or mould issue can range from a few hundred pounds to tens of thousands

Rising damp

This occurs when a building’s damp-proof course is breached or bridged. Raised flowerbeds, or paving against walls, can be a common bridge over the damp course. Rising damp can also occur if the building is built prior to around 1920, when the inclusion of damp-proof courses became commonplace. The appearance of damp patches and the presence of hygroscopic salts on wall surfaces could indicate the presence of rising damp. These salts pull in excess moisture from the air and make the wall surface damp; even when humidity levels are low, the wall remains damp because the salt is retaining moisture.  

Provisions for rising damp should be made during the construction or renovation phases of a school property and, if it does not have a damp-proof course, one should be considered. In buildings containing them, it’s vital to ensure that external ground levels are a minimum 150mm below the current damp-proof course. If not, this can result in bridging, whereby damp enters brickwork or mortar above the damp course – never run hard paving or decking right up to a wall. It is also important to ensure there are sufficient air bricks to provide ventilation to the timber sub-floor, and that they are uncovered and located approximately every 1.8 metres apart. Checking the air bricks are cleaned out every year is also a good strategy. 

Penetrating damp 

This can take some time to become apparent. If the property is exposed to prevailing wind, rain can be driven into the masonry, which can then pass through solid walls into the plaster. The best way to ensure the school is guarded against penetrating damp is by applying a weather protect coating to the exterior of a property’s walls. This solution is a breathable, colourless, water-repellent treatment, designed to prevent penetrating damp on brick, stone and concrete walls. One single coat will penetrate up to 13mm into the wall and prevent rain from penetrating a property’s exterior for 20-30 years. This also has a positive environmental impact, improving the wall’s thermal resistance and protecting cavity wall insulation from moisture to heighten its performance. Tests have shown that energy savings of up to 29% can be achieved in solid wall construction by application of these coatings. 

According to the NHS, mould can produce allergens, irritants and toxic substances

When mould becomes an issue 

If one of these forms of damp is allowed to thrive, mould could become a serious issue. One of the best ways to treat it is with positive pressure ventilation systems, or heat recovery fan systems. Positive pressure ventilation is the ultimate method to treat condensation problems and help reduce black mould; it is perfect for a building-wide solution. Designed to improve air quality and ventilation, it draws in clean dry air from outside, making the property slightly pressurised. The moisture-laden air is then forced out through gaps under doorways, around windows, etc, reducing humidity levels. In winter, a heating element linked to a thermostat is used to pre-warm the incoming air. 

The fresh dry air eventually pushes out all damp, stagnant air, leaving the property healthy. You can generally see the effects of positive pressure after four-six weeks. If the property has suffered from condensation mould, this can now be simply washed down with a mild sterilising solution, or hot soapy water with a small amount of bleach added. 

In conclusion

The cost of repairing a damp or mould issue can range from a few hundred pounds to tens of thousands. Prevention is absolutely better than cure, so be diligent in checking your property for any signs of damp or mould growth; if you’re unsure, contact a trained property care professional. Any delayed action could result in an unhealthy living environment and further structural damage. 

Richard Walker is national technical and development manager at Peter Cox

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