Double Curtains

Most advice on this treats it as a decorating choice — pick two colours, buy two sets, hang them. It isn't. It's a hardware decision and a measuring decision, and the fabric comes third. This page is how the thing is actually built. If you're still choosing between the two fabrics, read sheer and blockout curtains first.

What a double curtain actually is

Two curtains. One window. Two channels of track, so each layer moves without dragging the other one with it. That last part is the whole point, and it's what separates a double curtain from a lined one.

A lined curtain is a single curtain with backing fabric sewn to it. It draws as one piece, so you get the blockout or you get nothing. A double curtain gives you three positions instead of two: both open, sheer only, or both closed. In a north-facing living room on the Gold Coast that middle setting is the one you'll use for most of the year.

You'll see the same thing sold under half a dozen names — layered curtains, double curtains with sheer, blockout and sheer curtains, or just "sheers and drapes". The Americans spell it blackout. It is all the same build.

Put the sheer behind, not in front

The sheer goes on the back channel, against the glass. The blockout goes on the front channel, against the room.

I'll grant the counter-argument, because it is common in Australian showrooms: a sheer in front looks softer. It hazes the blockout, hides a hard colour, and photographs beautifully. If the window is decorative and neither layer will ever be closed, do it.

For a window you actually operate, it's the wrong way around. The blockout is the layer you close at night, so it should be the one you can reach without pushing fabric aside, and it needs to sit as close to the room as the track allows so it can overlap at the centre and return to the wall. Light escapes around a blockout curtain far more than it comes through one, and a sheer stretched in front does nothing about that. A sheer on the outside channel also takes all the sun. It's the layer that fades.

One exception worth naming. If the back layer is a blind rather than a curtain — a roller behind a sheer — then the sheer is in front by definition and that is correct. That is a different build with different clearances, and it's covered in blinds with sheer curtains.

Measure the reveal before you order anything

This is where double curtains go wrong, and it goes wrong at the quote stage rather than on install day.

A double track needs more depth than a single one, and the number you need is not the distance between the two channels. It's the distance the front curtain needs to clear the stacked back curtain — the sheer bunched at the end of its run is many times thicker than the sheer hanging flat. Fit the two tracks to each other and the blockout will brush the sheer every time it moves. Over a few years that's a wear mark on the fabric and a hesitation in the glide.

So measure the depth of the reveal, glass to the face of the wall, and tell whoever is quoting you. Three things follow from that one number.

• A deep reveal takes the whole thing inside. Both tracks sit in the recess, the treatment looks built-in, and you lose nothing to the room.
• A shallow reveal pushes the track onto the face of the wall or the ceiling. That's not a failure — a ceiling-fixed track running wall to wall is the better look in most modern rooms anyway. It just has to be decided before anything is made.
• No wall either side means no stack space. Two layers have to park somewhere when they're open. If there's 100mm of wall beside the window, both layers will sit over the glass all day and you will have paid for a view you can't see.

While the tape is out, measure to the wall rather than to the window. A curtain made to the size of the glass leaves a bright halo around the opening at six in the morning, and no amount of fabric weight fixes it. Windows are the weakest thermal point in most Australian homes, and a curtain that seals the whole opening is doing more work than one that covers the pane.

The second layer does not cost you twice

Nobody publishes the arithmetic on this, so here it is.

Curtains are priced on the fabric they consume, and fabric consumption is set by the fullness ratio of the heading — how many metres of flat fabric go into one metre of finished track. Ours are fixed. Wave fold runs 2.3 : 1. Box pleat, reverse pleat, gathered and knife pleat all run 1.8 : 1.

Put a 3-metre track in front of that. A wave-fold sheer takes 6.9 metres of fabric. A reverse-pleat blockout on the same track takes 5.4 metres. That's the real number your quote is built on, and it's checkable — ask for it, and if the answer is vague, ask someone else.

What the second layer does not add is a second set of everything. One measure, one track run, one install visit. Sheer and blockout curtains are both 2 to 4 weeks from check-measure to installation depending on the fabric, so the second layer doesn't add a week either. The quote comes back within 24 to 48 hours, itemised component by component — so you can see what the sheer costs on its own and decide whether it earns its place.

What is holding it up matters more than what is hanging

Two layers of fabric across a wide opening is a real load, carried by a handful of screws. And a track fixed into plasterboard alone will fail. Not might — will. It is a question of when, and the answer is usually the winter after the warranty conversation would have been easy.

We've been called out to more than one track that pulled out of a ceiling six months after someone else installed it. The curtains were fine. The fabric was good. The fixing went into 10mm of plasterboard and nothing behind it, and two layers of blockout pulling on it every night found that out.

What that means for you is a job at the measure, not at the install. Whoever quotes should be finding the joists or the batten above your opening before they price the curtain track, and telling you if a batten has to go in. Two layers is exactly the case where that stops being a formality.

The other thing to settle early is operation. Two layers can mean two cords or chains at one opening, and corded window coverings are covered by an ACCC mandatory standard for good reason. In a child's room, specify a wand or motorisation on both layers and remove the question.

When one layer is enough

Plenty of windows do not need this, and it is a reasonable amount of money to spend on a room that was never going to use the second layer.

• Rooms you're not in after dark. A study, a hallway, a formal dining room used four times a year. The blockout layer earns its money at night and at 5am in January. If neither of those happens in that room, a sheer on its own is the honest answer.
• Bathrooms and laundries. Fabric and moisture are a poor combination, and two layers of it is twice the problem. Bathroom windows want a shutter or a blind.
• Windows with no stack space and no depth. If the reveal is shallow and there's no wall either side, you are forcing two layers into a space that can hold one well. One layer done properly beats two done badly, every time.
• Where a blind is already doing the blockout job. If there's a blockout roller in the reveal, adding a sheer in front of it is the cheaper and better move.

And on a west-facing window, be realistic about what a sheer is for. It softens glare, it does not stop heat — shading works best on the outside of the glass. If the room is genuinely hot, an external blind or an awning does more than any indoor fabric will.

Frequently asked questions