Mould Problems

Help & Guidance for Homeowners

Mould issues & problems in homes

Mould problems associated with excess moisture and condensation within homes & properties are a common concern. Thankfully, in most cases, the mould is fairly minor & localised meaning small changes to the home/building environment (possibly some surface treatment too) can resolve the problem. However, there are increasing numbers of properties suffering more severe mould problems as modern lifestyles tend to generate more moisture in our homes and lock it inside (increased insulation, reduced ventilation).

Below, we try to explain a little bit more about moulds, treatment and why mould growth in domestic buildings is the most common cause of complaints regarding poor living conditions/poor indoor air quality.

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Why is the mould occurring in my home?

The presence of mould on surfaces within homes or buildings is a diagnostic indicator for high humidity conditions caused by excess atmospheric moisture trapped within the property. However, there are underlying building issues that can also lead to the presence of mould such as plumbing leaks or moisture ingress (penetrating damp) through faults in the masonry/brickwork.

What exactly are the moulds in my home?

Moulds are a primitive type of fungi increasingly reported as a problem in UK homes. Their presence is usually revealed when distinctive fruiting bodies appear on affected surfaces and it is these that release spores into the air. Mould spores occur naturally in the air but they will only germinate & grow where there is a suitable substrate (e.g. fabric, plaster, grout, timber) and a high surface humidity (sustained over time). For this reason we most often find mould growing on walls and ceilings in kitchens and bathrooms especially when there is poor ventilation, but also on food well past its sell-by date in the fridge!

Condensation - mould problems - PCA

The presence of mould may indicate an underlying problem

There are lots of different species of mould, but for day-to-day purposes, most people (including building surveyors) often just describe them based on the colour of the fruiting bodies, i.e. ‘black mould’ or ‘green mould’. This might seem a bit unscientific, but when it comes to the building, the details of mould species x, y or z are rarely as important as the location and distribution of the mould. This can help tell a surveyor whether there is an underlying building defect causing mould growth (e.g. a cold bridge → condensation) or just a failed or blocked extract fan etc.?

Moulds at home & its impact on health

There’s a lot of information on many websites regarding severe mould problems in homes and the ill-health effects associated with it. But we need to be careful because the ill-health effects reported are not necessarily caused by the mould spores themselves but by the underlying conditions in which they grow. What we can say with confidence is that you are more likely to have respiratory problems(infections, allergies or asthma) as a result of living continuously in damp, poorly ventilated conditions and these conditions are almost always signalled by the presence of mould.

In order to better understand the potential health effects, we can consider two completely separate potential health impacts; allergic responses and respiratory diseases.

+ Allergic responses to mould:

All mould spores have the potential to cause some degree of irritation to building occupants but it isn’t always possible to differentiate between this and other general indoor air quality issues. That is to say, the symptoms are very general and could easily be attributed to other irritants like normal household dust (especially house dust mites) or diesel fumes or even high carbon monoxide gas levels [Link to Paula article?]. This is not to say the allergic potential of mould spores should be ignored, especially for occupants who may be somewhat asthmatic, and it may be that for certain mould species and susceptible individuals the symptoms can be acute (rarely, throat lesions).

+ Respiratory diseases:

There are no documented respiratory diseases in humans related to mould per se. That is, moulds are not pathogenic in the same way as infections such as TB (bacteria) or Covid-19 (virus). Nevertheless, one of the main causes of mould in buildings, namely chronically high humidity, is known to make exposure to and infection by such agents of disease more likely. This means that it’s extremely unlikely that mould spores themselves can explain or be the cause of an infectious disease which may require e.g. anti-biotics but, as explained, the presence of mould is always a sign of excess humidity in buildings which is itself a stimulus to other infectious agents.

Treating mould problems in properties

For most properties suffering from mould problems, there are two main remediation approaches (see separate pages for advice on reducing the effect of cold bridges i.e. insulation/structural matters):

Reducing humidity and
Treating’ the mould (to remove spores and/or make surfaces more mould resistant).

Often these approaches are combined to achieve a long-term solution to the underlying causes of mould growth while dealing with the immediate concerns about mould spores in the air and the damage to painted surfaces. However, it is worth noting that unless you make sure you deal with point 1 (Reducing humidity), any form of mould & condensation treatment will fail.

Mould Problems - due to fault in building - PCA

What you can do to treat the mould

When it comes to excess trapped moisture being the source of the mould problem, the best outcomes are normally achieved through a combination of measures; heating, insulation and ventilation.

When treating the mould directly, it can provide short to medium-term benefits especially if the mould has been severe. So what treatments are available?

+ Surface biocidal sprays:

Most of us know that mould can be removed from most surfaces using chlorine bleach, but it is not ideal from a safety point-of-view, has a distinctive smell and does not provide any residual protection. Professional mould treatments will involve using specialist biocides usually in a 2 or 3-stage process (clean, prepare, protect - different biocides will often be used at each stage). But there are DIY products available from most hardware stores too. These are usually based on a well known surface disinfectant called Benzalkonium chloride (or similar)..

+ Surface stabilisation:

Mould-affected plaster surfaces normally require some degree of repair or stabilisation before re-decoration can start. There are a number of DIY products sold as primers, but these rarely contain any inhibitory biocides. Specialist mould resistant specifications will usually include a combination of resins and biocides to both bind the surface and provide a base layer of protection against re-colonisation by moulds (when/where humidity remains high)

+ Paint film biocides:

Most manufacturers produce special products claiming to be suitable for use in damp areas (“Kitchen and Bathroom paint”) and one of the features of these is the inclusion of booster biocides to prevent mould spore germination. Specialist treatment companies may also be able to offer additives that further enhance the performance of such paints.

Tips to Control Moisture

For helpful tips on helping to control condensation and excess moisture, visit our ‘How to Stop Condensation’ page

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The importance of ventilation

Learn more about why it is important to keep your home ventilated and healthy?

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When a building fault is causing the mould

Where it has been identified that the cause of your mould problems is due to a fault within the fabric of your property, the primary ‘cure’ for the mould problems is to resolve the underlying causes of the excess moisture (or condensation). This could be achieved in a number of ways however, the best approach is likely to be specific to each building and taking in a variety of factors such as 'occupancy patterns', etc. If the building has been identified as at fault, then we do recommend the property is inspected by a qualified PCA member surveyor.

Thinking you need a little bit more help?

Mould within our homes is unsightly and, potentially, unhealthy. Where it persists, we recommend a specialist surveyor is engaged to explore the root cause of the problem so they can provide advice or propose solutions to rectify the problem. If you are thinking this is something you’d like to consider, PCA specialists are there to help.

Members of the Property Care Association are at the forefront of knowledge and expertise when it comes to condensation and dampness issues. All contractors working under the PCA banner have been vetted and assessed to ensure that they are capable of surveying properties and identifying the appropriate solutions to resolve excess moisture, air quality and condensation problems. To find a PCA member close to you, simply run a search using the box below.

Why use a PCA Member - Experts in their Sectors

Trustmark Protection

Because of the high standards of service and quality that is expected from PCA members, all PCA contractor members have Government's TrustMark accreditation.

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PCA Promise

Our PCA Remedial Work Promise to homeowners WHILE WORKS TAKE PLACE at your property. Extra re-assurance & 'peace of mind'.

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Other related information

PCA's homeowner section
Damp problems
Penetrating damp
Rising damp
Condensation guidance for professionals
About the PCA