What Causes Mouldy Curtains and Linings…
…And How To Stop It Happening Again
If you’ve ever spotted mould patches on the back of your curtain linings – usually low down, in the corners, or anywhere the fabric sits close to a wall – you’re not alone. This is incredibly common in UK homes, especially in winter and especially in coastal areas like Poole and Bournemouth where humidity levels are naturally higher.
The good news? It isn’t caused by the curtains themselves. And it’s almost always preventable with a few small tweaks. Let’s walk you through what’s really going on – and what you can do about it.
What Actually Causes Mould on Curtain Linings?
Curtains don’t create mould. But the environment behind them can. When curtains sit too close to cold surfaces such as windows, external walls or recesses they trap a pocket of air behind the fabric. This trapped air quickly becomes:
- Cooler
- More humid
- Poorly ventilated
That combination is perfect for mould growth on the lining. It’s the same principle as condensation on windows: cold surfaces + trapped moisture = mould.
Why the Corners Are the Worst
The bottom corners of windows are:
- The coldest areas of the wall
- Where condensation naturally collects
- Where airflow is weakest
- Often slightly shaded by curtain folds and tiebacks
So the fabric absorbs this moisture and mould appears. This is why mould often looks like it ‘climbs’ from the bottom up.
Why We Recommend a 1cm Floor Height & Avoid Recess Installations
1cm above the floor
This small gap is incredibly important because it:
- Keeps the hem from sitting in damp areas
- Prevents moisture wicking into the lining
- Allows air to circulate underneath the curtain
- Reduces long-term damage to the fabric
Even a few millimetres make a difference.
Avoiding recess installations
Recesses trap cold air and if curtains are fitted inside a recess:
- There’s no airflow
- The glass is colder
- Condensation collects at the bottom
- Moisture sits directly behind the fabric
- Mould forms far more quickly
This is not a problem with the curtain, it’s the microclimate behind it. For this reason, we almost always recommend fitting curtains outside the recess so the fabric can breathe properly.
What Makes Curtain Mould More Likely?
Here’s what increases the risk:
- Indoor humidity above 60–65%
- Closed rooms (bedrooms especially)
- Curtains touching the wall, frame, sill or floor
- Furniture pushed tightly against external walls
- Poor ventilation
- Drying clothes indoors
- Trickle vents closed
- Older, colder properties
- North-facing or shaded rooms
These are environmental issues, not curtain defects.
How to Prevent Mould on Curtain Linings
- Keep humidity between 50–55%. Use a hygrometer or dehumidifier.
- Keep curtains slightly forward from the wall or window. Aim for a small air gap behind.
- Keep curtains 1cm above the floor which prevents moisture wicking.
- Avoid recess fitting especially in high-humidity homes.
- Open curtains daily. This lets the trapped pocket of cold air escape.
- Wipe condensation each morning in winter to stop moisture from rising into the fabric.
- Leave trickle vents open. These massively reduce trapped moisture, with minimal heat loss.
When to Be Concerned
You should look into a bigger issue if:
- There is heavy mould appearing rapidly
- The wall behind the curtain feels wet or cold to the touch
- Furniture or skirting boards are moulding
- You see damp patches spreading beyond the window area
In those cases, it may be:
- Hidden condensation issues
- Thermal bridging (cold spots in the wall)
- Rising damp
- Extremely high indoor humidity
We’re always happy to point you toward reliable local window or damp specialists if needed.
Our Honest Approach at Ashley Blinds
We want our customers to enjoy their curtains for years. That’s why we’ll always give practical, honest guidance, even when the issue isn’t caused by the product. We don’t brush customers off; we explain the ‘why’ and help them fix it.
And because we’re in coastal Dorset, we understand humidity issues in local homes better than most. If you ever have questions about how your curtain style, fabric, or placement could affect airflow, just ask: we’re here to help.
If you’re seeing condensation on your windows as well as mould on fabrics, read our blog post that explains the causes and solutions.
Got a question? We have the answer
Why Choose Ashley Blinds?
We’re a second-generation family business based in Poole, working across Dorset and Hampshire. With over 25 years’ experience, we pride ourselves on honest advice, quality products and personal service.
We don’t just sell blinds, curtains and shutters: we help you find the right solution for your home and lifestyle, so it looks good and works beautifully all year round.
