If you’ve found mould on walls, ceilings, window frames, or behind furniture, you’re not alone. In most UK homes, mould is a symptom of persistent moisture and cold surfaces, not a “random” cleanliness issue. It often shows up where air stays still, surfaces stay cold, and moisture can’t clear properly.
This page is the starting point for mould problems on CondensationGuide. The aim is to explain why mould appears, why it so often comes back after cleaning, and what tends to stop it long-term without turning the subject into panic or blame.
What mould usually means in a UK home
Mould needs two things to take hold: moisture and time. The moisture is commonly caused by condensation that forms repeatedly on cold surfaces, particularly in winter. Once surfaces stay damp for long enough, mould spores that are already present in normal indoor air can settle and grow.
Mould can look dramatic, but it’s rarely the “first problem”. It’s the visible sign that an area is staying damp more often than it should. Treating the mould without changing that damp pattern usually leads to repeat growth.
Why it often comes back after cleaning
Cleaning removes what you can see, but it doesn’t change the surface temperature, airflow, or humidity that allowed mould to form. In many homes, the same corner, window edge, or furniture zone stays cold and slightly damp each day, so mould simply re-establishes once conditions return.
This is why people often feel like they are “fighting mould” rather than solving it. The job is not just cleaning. It’s changing the conditions that keep feeding it.
Start with the situation that matches where the mould is appearing
If mould keeps returning in corners or along ceiling edges, it usually points to cold surfaces and weak airflow in those junctions. Start with condensation and mould in corners and on ceilings to understand why those areas are vulnerable and what tends to change the outcome.
If the mould is mainly behind wardrobes or large furniture against external walls, it often reflects trapped air and a colder wall surface rather than a leak. Start with mould behind wardrobes and furniture, which explains why it forms in hidden spaces and what usually prevents it returning.
If mould appears alongside wet windows or heavy morning condensation, it often sits on the same moisture pathway rather than being a separate problem. In that case it helps to start from the condensation side first, via condensation problems in UK homes, then return to the mould pattern once the moisture source is clearer.
When to step back and check what kind of damp you’re dealing with
Mould is most commonly linked to condensation, but it isn’t the only moisture source. If you’re seeing persistent damp patches that don’t follow seasonal patterns, plaster breaking down, staining that spreads even in warmer weather, or moisture that seems present even when ventilation and heating are reasonable, it’s worth stepping back before assuming it’s “just mould”.
In those situations, use the condensation diagnosis to separate everyday moisture patterns from issues that may need further investigation.
What usually stops mould long-term
In most cases, mould stops returning when the underlying damp pattern is changed. That usually means reducing indoor moisture build-up, improving ventilation in a controlled way, and preventing key surfaces from becoming cold enough to collect condensation day after day.
The best results typically come from a steady approach rather than extreme measures. Small changes that are kept consistent often beat drastic interventions that only happen once.
For a broader explanation of how condensation, mould and damp relate to one another, and why these problems are so often confused, the condensation, mould and damp guide brings the full picture together in one place.
In summary, mould is rarely the root problem. It’s a sign that moisture is lingering where it shouldn’t. The sensible next step is to start with the situation that matches where the mould is forming, then work outward only if the pattern doesn’t make sense or doesn’t respond.