Damp vs Mould:

When we talk about “damp,” we don’t just mean any presence of water or moisture – because all buildings and the air inside them contain some level of moisture. This is completely normal. In fact, moisture is part of the natural balance of indoor air and building materials. Dampness becomes a problem when the level of moisture rises above what’s considered safe or acceptable, either in the air or within building materials. At this point, it may begin to cause:

Mould is a type of fungus that thrives in damp environments, particularly where there is poor ventilation and little air movement. Mould spores are present in the air all around us, but they grow and multiply when moisture levels are too high for too long.

Mould is often a symptom of an underlying damp problem - not a cause in itself. It’s most commonly linked to condensation, although it can also appear alongside insulation defects or leaks. Interestingly, mould does not usually grow where the walls are very wet, such as with rising damp or plumbing leaks - those conditions are often too saturated for mould to establish.

It’s important to distinguish between normal and problematic moisture levels:

In the air (Relative Humidity):

In building materials (Moisture Content by weight):

These figures offer general guidance, but accurate diagnosis in real homes requires an understanding of context, building materials, and environmental conditions.

Dampness can enter or develop within a building through several distinct mechanisms. Understanding the differences is key to ensuring that repairs are appropriate and effective.

Environmental Damp (Condensation) - Caused by moisture in the air condensing on cold surfaces. It’s often a result of poor ventilation, underheating, or drying clothes indoors. This is the most common cause of mould, especially black mould around windows and in corners.

Cold Bridging (Thermal Bridging) - Occurs where insulation is missing or inadequate, such as around window reveals or structural junctions. These cold spots attract condensation, often causing mould growth even if the rest of the room is well heated.

Penetrating Damp (Rainwater Ingress) - Results from defects in the building’s external envelope - such as cracked render, porous brickwork, or broken gutters. Rainwater soaks through walls, typically causing localised damp patches that may worsen during wet weather.

Rising Damp - Ground moisture is drawn up through walls by capillary action when a damp-proof course is missing, bridged, or failed. It usually affects ground floor walls to a height of up to 1 metre and is sometimes misdiagnosed.

Traumatic Damp (Plumbing Leaks) - Caused by internal water leaks, such as from pipes, baths, tanks, or appliances. This type of damp can develop quickly and often shows as staining or damage below bathrooms or kitchens.

Mixed Conditions - In some homes, especially those with historic or complex construction, two or more damp types may be present simultaneously. For example, condensation from poor ventilation may be made worse by cold bridging and under-insulation.

Mould is typically associated with condensation and environmental conditions within the home. It thrives in:

In contrast, very wet walls, such as those affected by rising damp or leaks, are often too saturated and salt contaminated for mould to grow - though these conditions still pose serious problems for the building fabric and should be addressed promptly.

In Devon and the South West, many properties are particularly vulnerable to damp-related problems due to:

Damp and mould issues can be particularly persistent in homes where modern materials meet traditional methods - and each situation requires a tailored approach.

In some cases, simple damp or condensation issues can be resolved with a sensible DIY approach, especially if you make use of reputable online resources, guides, and homeowner forums - though it’s important to be cautious and avoid quick fixes that might mask rather than solve the underlying cause.

While there are general rules of thumb for identifying damp, diagnosing the true cause can be complex. Moisture readings, surface temperatures, construction details, and occupant habits must all be considered.

If your home has ongoing damp or mould issues, or if previous treatments haven’t worked, it’s important to consult a suitably qualified and competent person. This could be:

Any reputable surveyor should be aware of and work within the principles set out in the Joint Position Statement on Damp and Mould, published by the RICS, Historic England, PCA, and other industry bodies. This promotes a holistic, evidence-based approach to investigation - one that considers the building fabric, environmental conditions, occupancy patterns, ventilation, heating, and maintenance history before recommending action.

Damp and mould are not just cosmetic issues - they can damage your home, harm your health, and increase living costs. But with the right diagnosis, these issues can be tackled effectively.

Remember: not all moisture is a problem - it’s only when levels rise above what’s safe that action is needed.

If you’re unsure about what’s causing the issue in your home, or if damp keeps returning despite attempts to treat it, we’re here to help. Nova Surveyors provide expert, impartial advice to help you make informed decisions.

📞 Contact us today to book a damp and mould survey or learn more about how we can support your property.

🔍 Serving homes across Devon, Somerset, and the South West.