We loved our linen curtains and hated what they let through. A west-facing bedroom takes the evening sun straight in the face from about six, and in June the sky is bright again by five in the morning, which is not a time any reasonable person wishes to meet. Replacing the linen with a heavy blackout fabric would have fixed the light and ruined the room; linen is the whole softness of the space. The answer was to keep the linen exactly as it was and add a separate, detachable blackout lining that hangs behind it on its own hooks.

Why a detachable lining, not a sewn one

You can buy curtains with blackout sewn permanently to the back, and you can pay to have it added to yours. We did neither, because a sewn lining changes how linen hangs — it stiffens the drape, adds weight that drags the heading, and makes the whole curtain a chore to wash. A detachable lining hangs on the same hooks behind the curtain as an independent layer. The linen still moves like linen. The lining does the blocking. Either can be taken down and washed alone.

The detachable approach also lets you tune the room by season. In winter we sometimes leave the lining off entirely and let the low sun in; in June it is essential. A sewn lining is a permanent decision; a hooked one is a setting you can change in two minutes.

A detachable blackout lining hanging on curtain hooks behind a linen curtain, shown from the side Save
Two independent layers on the same hooks.

Getting the width right

The single most common blackout failure is light leaking down the sides, and it comes from a lining cut to the glass rather than the wall. We cut the lining 150 mm wider than the window on each side and hung the rail to overlap the reveal, so the dark layer runs well past the frame. Light takes the straightest path it can; give it no gap at the edge and the room goes properly dark.

Length matters less for darkness but a lot for looks. We hung the lining 20 mm shorter than the linen so it never peeks below the hem, and let the linen pool a finger's width on the floor as it always had. From inside the room you see only linen; the blackout is a secret layer doing its work behind.

A curtain rail overlapping the window reveal with the blackout lining running past the frame edges Save
Run the dark layer past the frame — light takes the straight path.
“A sewn lining is a permanent decision; a hooked one is a setting you can change in two minutes.” — Mira

The top edge and the last of the light

Even with width sorted, light skims over the top of most curtains where the heading sits proud of the rail. We closed that gap with a simple pelmet — a 120 mm strip of painted MDF fixed above the rail — which caps the light that would otherwise spill down the wall at dawn. It is the least glamorous part of the project and the one that took the room from dim to dark.

The result is not a blacked-out box; it is a soft linen room that happens to be dark when we want it to be. The evening sun no longer bleaches the bed, the June dawn no longer wakes us, and on a grey winter afternoon we can lift the lining off in a minute and let the low light back in. Two layers, one decision we can change at will.

  • Three-pass blackout lining — the coating is what makes the room truly dark.
  • Cut the lining 150 mm wider than the window each side; hang past the reveal.
  • Lining 20 mm shorter than the linen so it never shows below the hem.
  • Cap the top with a slim pelmet to stop light skimming over the heading.

How to do it

Measure to the wall, not the glass.

Window width plus 150 mm each side; drop from the rail to a finger above the floor. Blackout fails at the edges, so over-size the width.

Measure to the wall, not the glass.

Hang the lining on its own hooks.

Detachable blackout lining hooks onto the same gliders behind the linen, as an independent layer. The linen keeps its drape.

Overlap the reveal.

Extend the rail so the curtains and lining run well past the window frame on both sides. Close the side gap that leaks light.

Cap the top with a pelmet.

A 120 mm painted MDF strip above the rail stops light skimming over the heading at dawn. The detail that finishes the dark.

Frequently asked

Will the linen still look like linen?
Yes — the lining hangs separately, so the linen drapes and moves exactly as before. From inside the room you see only the linen layer.
Can I wash the layers separately?
That is the main advantage. Linen washes on its own gentle cycle; the blackout lining wipes clean or washes cool and air-dries. Neither compromises the other.
Do I need a pelmet?
Only if dawn light over the top bothers you. For a north or east room the width fix alone is often enough; for a bright west or south room the pelmet earns its place.
One-pass or three-pass lining?
Three-pass for a bedroom you want genuinely dark. One-pass dims but still glows at the edges on a bright morning.
Can renters do this?
Yes — the lining needs no fixing of its own beyond the existing hooks. Only the optional pelmet involves a couple of screws, which fill at move-out.
Will it help in winter too?
Yes for warmth — the extra layer cuts heat loss through the glass. And you can remove it entirely on dim days to let the low sun in.
What about light under the curtain?
Let the linen pool a finger's width on the floor and the bottom seals itself. A lining that floats above the floor leaves a glowing line at the hem.

In closing

We kept the curtains we loved and lost the light we did not want. The bedroom is soft linen by day and properly dark by night, and the difference between the two is a layer we can hook on or lift off in a minute. The June dawn still arrives at five; we just no longer have to be there for it.