In most cases, recurring mould is a sign that the conditions allowing it to grow haven’t changed. Cleaning removes what you can see, but it doesn’t address why moisture keeps settling there in the first place. Before assuming a more serious damp issue, it helps to check where this sits within a wider condensation diagnosis.
What’s actually happening
Mould grows when surfaces stay damp often enough for long enough. In UK homes, that dampness is most commonly caused by condensation forming repeatedly on cold or poorly ventilated surfaces.
When warm, moisture-laden air meets a surface that’s cooler than the surrounding room, water forms on that surface. If this happens regularly, even in small amounts, mould spores can establish and regrow after cleaning.
The key point is that mould is the result, not the cause. Unless the moisture pattern changes, mould has the opportunity to return.
The most common reasons mould comes back
Persistent condensation is the most likely reason. This often affects corners, ceiling edges, window surrounds, and external walls, particularly in colder months. Even if the room feels dry most of the time, brief periods of condensation can be enough.
Cold surfaces make condensation more likely. Poorly insulated walls, ceiling junctions, and areas behind furniture can stay significantly colder than the rest of the room.
Restricted airflow allows moisture to linger. Furniture tight against external walls, sealed bedrooms overnight, and limited ventilation all contribute to localised dampness.
Whole-home moisture build-up can also play a role. When humidity is high throughout the property, mould may appear in several locations even if no single room seems particularly wet.
Why mould sprays and bleach usually fail
Mould sprays kill surface growth, which is why walls often look better immediately after cleaning. However, they don’t warm cold surfaces, improve airflow, or reduce moisture in the air.
As soon as condensation forms again in the same spot, mould spores can regrow. This is why people often feel stuck in a cycle of cleaning and reappearing patches, especially through winter.
Repeated chemical treatment without changing conditions can also damage surfaces over time without solving the underlying issue.
What usually helps first
The least disruptive changes focus on stopping moisture from settling in the first place. Keeping rooms evenly heated reduces cold surfaces. Improving steady ventilation helps moisture escape before it condenses.
Where mould forms behind furniture, pulling items slightly away from external walls often makes a noticeable difference. For mould in corners or ceiling edges, improving heat distribution and airflow is usually more effective than surface treatments alone.
If mould is widespread across multiple rooms, addressing overall humidity and ventilation patterns tends to be more effective than treating individual patches.
When it may not just be condensation
Most recurring mould is condensation-related, but there are times when further investigation is sensible.
If mould persists through warm, dry weather, if walls feel actively wet rather than cool, or if plaster begins to break down, the problem may not be driven by condensation alone.
In those cases, it’s worth stepping back and reassessing whether moisture could be entering the building fabric rather than forming from indoor air.
Putting recurring mould into context
Recurring mould usually means the environment hasn’t changed, not that cleaning has failed. Once moisture patterns are corrected, mould often stops returning rather than needing constant treatment.
If mould appears mainly in corners or along ceilings, see condensation and mould in corners and ceiling edges. If it’s behind wardrobes or large furniture, mould behind wardrobes and furniture explains why those areas are especially prone. If the issue affects multiple rooms, whole-house condensation may better match what you’re seeing.
For a wider explanation of how condensation, mould and damp relate across a property, the condensation, mould and damp guide brings these patterns together.