How to Stop Light Coming Through the Sides of Blinds

If you’ve invested in blackout blinds but still notice light creeping in around the edges, you’re not alone. Light gaps are one of the most common complaints homeowners have about their window coverings. Whether it’s early morning sunlight or streetlights at night, even small gaps can disrupt sleep and reduce privacy.

The good news is that there are practical solutions. Here’s how to stop light coming through the sides of blinds — and how to prevent the problem altogether.

Why Do Light Gaps Happen?

Light gaps usually occur for one of three reasons:

Blinds are too narrow for the window recess
The blind is mounted outside the recess incorrectly
The blind design naturally leaves small side gaps

Many ready-made blinds are manufactured in fixed sizes. If your window doesn’t perfectly match those measurements, small slivers of light can appear down either side.

This is particularly noticeable with blackout roller blinds, as the fabric must sit slightly narrower than the mechanism to operate smoothly. As a result, a small gap between fabric and wall is often unavoidable with off-the-shelf options.

Choose Made-to-Measure Blinds

The most effective way to reduce light gaps is by choosing made-to-measure blinds. Professionally measured and fitted blinds ensure the closest possible fit to your window frame.

A custom-fit roller blind installed within the recess will minimise side gaps compared to standard sizes. If maximum darkness is your priority — particularly in bedrooms — precision measuring makes a significant difference.

For even tighter coverage, some systems are designed to sit closer to the glass, reducing the amount of light that can escape around the edges.

Install Blinds Outside the Recess

If light control is more important than a flush, recessed finish, mounting blinds outside the window recess can help. This method allows the blind to overlap the wall area around the window, blocking more light from entering at the sides.

This approach works particularly well with blackout roller blinds. By extending the width beyond the recess by several centimetres on each side, you can dramatically reduce visible light gaps.

However, this option depends on wall space and aesthetic preference.

Consider Layering Window Coverings

Layering is another effective way to stop blinds letting light in. Pairing blackout blinds with curtains can eliminate side gaps almost entirely.

For example:

A blackout roller blind provides primary light control.
Curtains installed wider than the window frame block any remaining light.

This combination also improves insulation and enhances the overall look of the room.

Use Adjustable Blinds for Better Coverage

In some cases, adjusting your existing blinds can reduce light leakage. Venetian blinds and vertical blinds allow you to tilt slats or vanes to redirect incoming light. While they do not provide complete blackout coverage, they can reduce glare and improve privacy during early mornings or evenings.

For patio doors or wider windows, vertical blinds may offer better coverage than narrow alternatives, particularly when fitted correctly across the full span.

Check Installation and Alignment

Sometimes light gaps are caused by simple installation issues. If a blind isn’t level or centred properly, uneven gaps may appear on one side.

Checking bracket alignment and ensuring the blind sits squarely within the recess can sometimes resolve the issue without replacement.

If the problem persists, professional fitting may be worthwhile. A correctly installed blind should sit evenly and operate smoothly without excessive side gaps.

Are Complete Blackout Solutions Possible?

It’s important to understand that most standard blinds cannot guarantee 100% blackout due to necessary movement clearances within the mechanism.

However, modern blackout systems significantly reduce light infiltration when:

Properly measured
Correctly installed
Paired with suitable mounting methods

For bedrooms, nurseries or shift workers who require darker conditions, upgrading from ready-made blinds to professionally fitted blackout blinds often delivers noticeable improvements.

Create a Darker, More Comfortable Space

Light gaps in blinds can be frustrating, especially when they disrupt sleep or reduce privacy. Fortunately, there are practical solutions — from made-to-measure blinds and external mounting to layering window treatments.

If you’re struggling with blinds letting light in, reviewing your fit, installation method, and blind type could make all the difference. For advice, contact us at Val-U-Blinds for expert advice on all things blinds.