Why Blackout Curtains Still Let Light In: Tracks, Returns & Centre Overlap

You close the bedroom curtains, but a bright line remains between the panels. Light also curls around one side, or glows above the heading. The fabric feels substantial, so why is the room still bright?

Light gaps around blackout curtains often come from the installation rather than the fabric. Opaque material can block light through the panel while leaving routes around its top, sides, centre or hem. A different fabric alone may not solve those gaps.

This guide explains what curtain tracks, side returns and centre overlap do, how to recognise a repairable closing problem, and when alterations or another layer make sense. For Abu Dhabi bedrooms affected by strong daylight, the aim is to match the fitting to your required darkness without replacing useful curtains unnecessarily.

Find the light route before blaming the fabric

A blackout panel is not a sealed window covering

Curtains are moving fabric panels. Their folds, track position and closing arrangement affect whether the window remains covered when the curtains are drawn.

Manufacturer guidance distinguishes fabric light transmission from perimeter light: a standard curtain installation can admit light around an opaque panel. ^[1]

That does not automatically mean the product is faulty. A curtain specified mainly for decorative coverage may not meet the needs of someone sleeping during the day. Equally, a panel that no longer reaches its usual closing position could have a repairable problem.

Map the gaps with the curtains closed

From inside the room, look at the whole window before inspecting details:

• Above the heading: light may pass between the curtain top and ceiling, around brackets or through an open ceiling pocket.
• At the sides: the outer edges may stop in front of the window without turning back towards the wall.
• Between the panels: the leading edges may meet poorly, pull apart lower down or lack an effective overlap.
• Below the hem: the curtain may stop short of the intended coverage, or light may reflect beneath it.
• Across the fabric: confirm that the material or lining is actually specified as blackout, then check for damage or openings in the construction.

Record where the gap appears and whether it changes after opening and closing the curtains.

In Abu Dhabi, morning sunlight or lighting outside an apartment can make a small uncovered route noticeable. A balcony door also needs practical access, so the solution must work when the curtains are open as well as closed.

Buying only by the glass width is a common mistake. The curtain also needs to cover the chosen track, form its heading and accommodate any returns or centre arrangement. More fabric does not automatically mean that all those details have been resolved.

How tracks, returns and overlap change the result

Check the existing closure first

If the curtains previously closed satisfactorily, start with their condition. A missing hook, damaged glider, detached lining or obstructed track can affect how the panels hang and meet.

Gliders are the sliding carriers inside a curtain track; hooks connect many pleated headings to them. The heading is the top construction that forms the folds. Other heading systems use different attachments. ^[2]

Ask an installer to assess a dragging, catching or loose installation. Do not pull harder against a jammed track or remove safety components. A local repair or rehanging may restore the intended closure.

If the track and curtains are sound but the original coverage is insufficient, adjustment alone cannot create missing width or drop. Browse the Maintenance Guides before deciding between repair and alteration.

Control the top gap with the track and heading

A curtain track positions the moving panel; it is not automatically a light barrier. Ceiling mounting can bring the arrangement closer to the ceiling, but the fabric's finished top position still depends on the heading and attachments.

A suitable pelmet, a cover above the curtain, can obstruct a light route around the top. A properly planned ceiling pocket may also help conceal the track and reduce direct light paths. Neither should be assumed to seal the whole opening.

The installer must leave working clearance for the curtain to move without rubbing. Raising hooks too far, compressing folds into a shallow pocket or adding a cover that catches the fabric can create an operating problem.

Heading choice matters when space is limited, especially with separate sheer and blackout tracks. Manufacturer planning guidance treats single and double systems, recess fitting and stacking space as design decisions. ^[2]

Bring the outer edges back with curtain returns

A curtain return is the outer section of the panel that turns from the front of the track towards the wall or another planned end fixing. It helps cover the side route left when the curtain hangs away from the wall.

Extending a straight track beyond the window and providing a return are different actions. Extra width covers more of the opening from the front; a return addresses the space behind the outer curtain edge.

The return needs fabric allowance and a suitable attachment. Manufacturer fabrication instructions account separately for return length and its connection to the track. ^[3]

An installer should check the wall distance, heading and nearby handles before proposing a return. Simply pulling the last fold sideways may distort the heading or rob the front panel of coverage. Curtains cannot always be adapted without alteration or replacement hardware.

Overlap the centre instead of leaving a direct join

Centre overlap means one leading edge covers the other when a pair closes. Certain track systems use an overlap carrier, a leading component that positions one panel in front of the other at the meeting point. Manufacturer manuals distinguish overlap and butt-meeting arrangements. ^[3]

The hardware and fabric must work together. An overlap near the heading may leave a gap farther down if the leading edges twist or separate. Check the closed panels along their full height.

There is no single overlap allowance for every curtain. Heading, track design, fabric behaviour and intended closure all matter. Adding an incompatible overlap arm or forcing panels beyond their designed travel can make operation worse.

Review the lower edge and any second layer

A shorter curtain may leave the sill or lower glazing exposed. Alteration can help only if suitable fabric or making allowances are available. A fabric extension may change the appearance and should be discussed before work starts.

The finished drop should balance coverage, movement, cleaning and door access; floor-length curtains do not guarantee darkness.

If curtains are worth retaining but cannot achieve the required result alone, a suitable opaque blind behind them may add useful coverage. The blind can still have its own gaps, so compare the complete arrangement rather than assuming two products create a sealed room.

See Blackout Curtains vs Blackout Blinds: Which Works Best? for the wider comparison.

Choose a repair or improvement around your room

If your priority is fixing a recent centre gap, consider track and heading assessment first, because a displaced attachment or obstruction may be repairable.

If your priority is reducing side streaks while keeping the curtains, consider whether their width and hardware allow suitable returns. This can address a light route without changing every part of the installation.

If your priority is daytime sleep, consider top, side, centre and lower coverage together. Improving one edge may simply make another gap more noticeable.

If your priority is preserving a decorative pole, ask which return and closure options are compatible. A change to the heading or hardware may affect the look you want to keep.

These hypothetical examples need assessment, especially with shallow pockets, heavy panels or balcony doors.

Consider operation, care and permissions

An improved closure should remain easy to open. Confirm where the curtain stack will sit and whether windows, doors and handles remain accessible. Do not obstruct required ventilation or emergency access.

Motorisation moves the curtains; it does not automatically close every light path. Compatible leading carriers, correct panel dimensions and programming still matter. Any powered adjustment must follow the selected system's instructions, and mains-electrical work requires an appropriately qualified contractor.

Check cleaning instructions before altering a lining or adding attachments. Do not assume a lined blackout curtain is machine-washable. For tenants, obtain any required approval before moving tracks, attaching wall fittings or altering a ceiling pocket.

Where operating cords are present, ask for a safety assessment and retain the required devices. Favour operation without accessible cords where young children live or visit; tensioning alone does not remove every cord hazard. Keep cots and climbable furniture away from controls. ^[4]

For broader style choices, read Curtains vs Blinds: Which Is Right for Your Home?.

Care, repair and replacement checklist plus FAQs

Eight checks before changing your curtains

1. Locate the route: Is light coming through the panel or around the top, sides, centre or hem?
2. Record the history: Has the gap always existed, or did it follow damage, cleaning or a closing fault?
3. State the target: Do you want fewer bright lines or stronger room darkening for daytime use?
4. Check repair first: Are hooks, gliders, leading carriers, lining and fixings in suitable condition?
5. Confirm side details: Is there enough fabric and suitable hardware for the proposed returns?
6. Agree centre and top coverage: How will the full-height closure and fabric-top position work?
7. Protect everyday access: Will panels clear doors, handles and furniture, with appropriate safety and permissions?
8. Get the scope in writing: Confirm alterations, hardware, expected limitations, care, warranty terms and cost before proceeding.

Does a light gap mean my blackout fabric is defective?

Not necessarily. If light is passing around the panel, changing the fabric may leave the same gap. If it is visible through the material, check the fabric or lining specification and condition.

Can returns be added to existing curtains?

Sometimes. It depends on the available width, heading, track and end attachments. Ask whether the work is a simple rehanging adjustment or needs fabric alteration and new hardware.

How much should blackout curtains overlap at the centre?

Use the selected track and heading requirements rather than a universal figure. The panels need enough usable coverage to close without distorting, and the leading edges should be checked from top to bottom.

Will a ceiling track stop light above the curtains?

It may improve the arrangement, but the curtain's top position and available clearance still matter. A ceiling-mounted track alone is not a promise of complete darkness.

Do I need a pelmet or floor puddle?

Neither is automatically necessary. A pelmet may help with a top light route; extra fabric on the floor does not address side or centre gaps. Choose details around the problem and practical use.

Should I replace the curtains or add a blackout blind?

Retain sound curtains where they can be adjusted or complemented sensibly. Compare alteration with a suitable second layer, including its fitting and access needs. Replacement is more reasonable when the fabric, dimensions or hardware cannot support the required result.

Discuss the gap before replacing the curtains

Contact Blinds Depot Abu Dhabi with a photograph of the whole window, where light appears and how the curtains currently close. Ask whether repair, returns, centre overlap or improved top coverage could help. If you are planning a new installation, book a free consultation for professional measuring and tailored recommendations. ^[5]

Sources

1. Silent Gliss: Dimout and blackout fabrics
2. Silent Gliss: Curtain Planning Guide
3. Kirsch: Ripplefold Fabrication Manual
4. BBSA: Window-blind child safety
5. Blinds Depot: Free consultation