Where does the curtain go when the door is open?
That is the whole problem with French and bifold doors, and it is the question almost nobody asks until the curtains are up. A door is not a window. You walk through it, several times a day, often carrying something, and the curtains have to be somewhere else while you do.
Get that right and full-height curtains at a set of glazed doors look better than curtains at any other opening in the house. Get it wrong and you spend the summer pushing fabric out of the way.
Stack-back is the measurement that matters
Stack-back is the width the curtains take up when they are fully open and pushed to the side. It is not a small number. Gathered fabric bunched at the end of a pole occupies real width, and the wider the opening, the more fabric there is to park.
On an ordinary window, if the stack sits over part of the glass you lose a bit of light and most people never notice. On a door, the stack sitting over the opening means it is in your way every time you use the door.
So the pole or track needs to extend well past the opening on each side, far enough that the whole of the open curtain sits on the wall beyond the frame rather than over the glass. That extension is what makes the doors usable, and it is the thing that gets cut when someone orders hardware the same width as the doors.
Two things drive how much you need: how wide the opening is, and how full and heavy the curtains are. A fuller curtain in a heavier cloth stacks wider than a flatter one in something light, which is one reason to settle the heading before you order the hardware. The article on curtain fullness explains what changes.
Check the wall you are planning to stack onto
Wide glazed doors often sit in walls that do not have much to spare. Before you assume you can run the hardware past the frame, look at what is actually there on each side.
Common obstructions are a return wall or corner close to the frame, a radiator below, a light switch, a run of kitchen units, or a second set of doors. Where one side is tight and the other is open, drawing the curtains to one side only is often a better answer than an even pair. More on that below.
Also look up. You need somewhere to fix, and on a wide opening with a structural lintel or a plastered reveal, the fixing surface above the frame is not always where you expect it.
Handles and door swing
French doors usually open inwards into the room, which means the leading edge of the door sweeps through exactly the space the curtain wants to occupy. If the curtain hangs anywhere over the door, the door catches it.
Handles are the other trap. A lever handle stands proud of the door face by a useful amount, and a curtain hanging close to the glass will snag on it or sit oddly around it. Where the doors open inwards, the practical answer is usually to hang the curtains further forward of the door face than you would at a window, so the fabric clears the handles and the swing entirely, and to make sure the open stack is clear of the door arc.
Bifolds behave differently. The leaves concertina and stack against one jamb, so the folded doors themselves take up depth at one end of the opening. That folded stack and the curtain stack both want the same corner, and they need to be planned together rather than discovered on fitting day.
Sliding doors are the easiest of the three, because nothing swings into the room, but the handle clearance point still applies.
Track, pole, or ceiling
Both work. The decision is mostly about what the opening looks like and how much wall you have above it.
A pole is a strong horizontal line above the doors, which suits a room where you want the hardware to be part of the scheme, and it needs enough wall height above the frame for the brackets. Glazed doors often run close to the ceiling, so check that height early.
A track keeps the hardware out of sight and can be fixed very close to the ceiling, which is usually the better look on floor-to-ceiling glazing because the curtain reads as one uninterrupted drop. The article on ceiling-mounted tracks covers when that is the right call and what the ceiling has to be able to take.
Either way, a wide span needs adequate support along its length, and a heavy curtain over a long run puts sustained load on the fixings. Fit a centre bracket on any pole over 200cm and a third bracket over 300cm, which across a set of bifolds usually means both. Use passing brackets so the rings still travel the full width. Choose the diameter for the load rather than the look: 19mm and 25mm suit lighter curtains, 28mm covers most rooms, and heavy, interlined or full-height door curtains want 35mm or 45mm.
Maximum spans and load limits are set range by range, so take them from the product page for the system you are considering and from the supplier's fitting instructions rather than from a rule of thumb. Send us the width of the opening, the drop and the fabric through the contact form and we will check a particular range against them. Do not assume a length of hardware sized for a window will do the job across a set of bifolds.
You can see what is available in the curtain tracks collection and, for very wide runs, the extra long curtain poles.
One pair, or a single curtain to one side
The default is a pair meeting in the middle, and on a symmetrical opening with plenty of wall on both sides that is usually right.
A single curtain drawn to one side is the better answer more often than people think. It suits an opening where only one side has wall to stack onto, a bifold that always folds to the same end, and any door you use constantly, because there is only one curtain to move and it always lives in the same place.
The trade-off is that a single curtain for a wide opening is a lot of fabric in one stack, so it needs somewhere generous to go. Decide this before ordering, because it changes the widths.
Length
Curtains at doors are almost always floor length, and they need to clear the floor rather than sit on it, because a curtain that pools at the foot of a door you use daily gets walked on and dragged. Watch for a raised threshold at the door line, which can sit higher than the floor the curtain hangs over.
Getting it specified
Wide openings are where measuring errors get expensive, because the hardware, the stack and the door movement all have to agree. Work through the curtain measurement finder for the sequence, and use the free design consultation if the opening is unusually wide or the wall either side is tight. It is the right moment to have someone else check the numbers.