Measuring for bi-folds & large glazing
Long runs of glass and bi-fold doors are where curtain hardware is asked to do the most, and where stack-back, weight and where the fabric lands all matter at once. Here is how to measure them.
Bi-folds, sliders and floor-to-ceiling glass are the showpieces of a modern scheme, and the hardest thing to dress well. The span is long, the curtains are heavy, and the doors have to keep working. The measuring is not difficult, but it is unforgiving: three things have to be right at once: the run, the stacking space, and the drop.
Measure the full run, then the walls beside it
Start with the width the curtain must cover when closed: the whole glazed opening or door set. Then measure something people forget: the wall available on each side, beyond the glass. That side wall is where the open curtain has to live, and it is what makes the doors usable. On a wide opening a curtain can stack a long way to one side, often 60 to 70cm or more: so the more side wall you have, the cleaner the result.
Set the track length to clear the doors
Extend the track beyond the glass and into the side wall so that when the curtain is open it sits entirely off the doors. On bi-folds this is non-negotiable: if the stacked curtain overlaps the doors, they cannot fold. Decide early whether you want the curtain to part in the centre and stack both sides, or draw to one side as a single curtain: the side wall space you have often makes that decision for you.
The track has to clear the door operation, not just the glass. A bi-fold needs room to fold and a slider needs its leading edge free. Measure with the doors in mind, then check the curtain can stack without fouling them.
Why these runs favour a track and a wave heading
Over a long span, a track carries the weight without bowing, runs smoothly, and disappears against the ceiling line. Paired with a wave heading: a continuous, even ripple: the curtain stacks back tightly and predictably, which is exactly what a long run needs. Wave hangs from a compatible track or a glider pole rather than from rings; see our heading styles guide for how it differs from pleated headings.
Measure the drop, and respect the weight
For floor-to-ceiling glass the curtain is usually floor length, finishing around 1cm clear of the floor. Measure the drop in several places across the run and take the shortest, because the floor over a wide opening is rarely level end to end. Finally, match the hardware to the weight of a tall, lined curtain over a long span. Our diameter and weight guide covers where a pole stops coping and a track takes over.
On the longest runs, drawing heavy curtains by hand loses its charm quickly, which is where motorised tracks earn their place.
Common questions
Pole or track for bi-fold doors?
A track almost always wins on long door runs. It carries weight over a long span without sagging, runs smoothly, and with a wave heading the curtain stacks tightly off the doors. Poles look best on shorter, decorative windows.
Where should the curtain stack on bi-folds?
Onto the wall beside the doors, not across them. Extend the track into the side wall space so the open curtain clears the glass entirely and the doors can fold and open without fouling the fabric.
Why is wave the popular heading here?
Wave hangs in a continuous, even ripple and stacks back tightly and predictably, which suits long runs and floor-to-ceiling glass. It needs a compatible track or a glider pole rather than rings.
How much does a curtain stack on a wide opening?
It depends on heading and fabric, but a single wave curtain can stack a substantial amount, often around 60 to 70cm to one side. Allow generous side wall space so the doors stay usable.