Wide windows, patio doors and open-plan spaces all need poles well beyond the standard 120–180cm. Longer poles are straightforward, but they need planning — a long span behaves very differently from a short one.
Diameter matters more as span increases
The longer the unsupported span, the more a pole will bow under load. Diameter is the main defence.
For anything over about 240cm, treat 28mm as a minimum and prefer 35mm or larger, particularly with lined or interlined curtains. Metal carries more than timber at the same diameter, so if you want the look of wood on a very wide window, either go up a size or add extra support.
Support spacing is the critical detail
A long pole is only as good as its brackets. As a working guide, add an intermediate bracket roughly every 200cm, so a 300cm pole has three brackets and a 500cm pole has four.
If the curtains need to draw the full width, specify passing brackets and passing rings so the rings glide over each support rather than stopping against it. Standard centre brackets will block them.
See Curtain Pole Brackets Explained for the difference.
Jointed poles
Very long poles are often supplied in two or more sections with a connecting sleeve. This is normal and perfectly strong, provided a bracket sits at or immediately beside the joint. An unsupported joint is the first place a long pole will sag.
Check before ordering whether your pole is one piece or jointed, and where the joints fall relative to your bracket positions.
Think about the curtains, not just the pole
A very wide window means a lot of fabric. Two things follow.
Weight. A 400cm pair of interlined curtains is heavy. Weigh them if they exist; if not, err upward when choosing diameter. Our guide to hanging heavy curtains covers fixings in detail.
Stack. Open curtains on a wide window take up a lot of wall. Allow generous overhang at each end — 25cm or more — or accept that the curtains will cover some glass. On very wide spans, consider a pair per half rather than one enormous pair.
Fitting a long pole
Mark all bracket positions from a single level reference across the whole run rather than measuring up from the window at each point. Over 4 metres, a small error at one end becomes very visible.
Get help lifting. A 400cm pole with rings threaded is awkward and easy to bend.
Where to look
Browse Extendable & Double Poles and Metal Poles, or send us your measurements and we will tell you what will hold.