Bay windows are often the reason you fell for the place, and the reason you have been putting off curtains for a year. Three or five angled faces, a shallow recess, a radiator tucked under the sill, and nothing quite square to fix to. None of it is genuinely difficult, but the decisions need to be made in the right order. Get the measuring and the track right, and the heading and the fabric almost choose themselves.

Start With the Bay, Not the Glass

Most curtain advice assumes a flat window on a straight wall. A bay has to be measured along the line where the track will actually sit, which is usually well outside the window frame and often up on the ceiling of the recess. Use a steel tape throughout. Fabric tapes stretch and sag, and two centimetres out is the difference between a curtain that skims the floor and one that puddles behind the radiator.

Work round the bay in one direction and write everything down before you move on. Bays in older British terraces are rarely symmetrical. A century of settlement can leave one return noticeably longer than the other, which is exactly why you measure each face rather than assuming they match.

• Total width at the track line, from the wall on one side to the wall on the other
• Each angled face separately, corner to corner
• Any straight wall return either side of the bay
• Drop, from the underside of the track to your finished length — sill, radiator top or floor
• Sill projection, window handles and radiator position, so the curtains clear them
• The corners: note whether they look like 90 degrees, 135 degrees or shallower

If you are ordering made-to-measure, supply the measurements face by face and say how many corners there are. If you are doing it yourself, cut a scrap of card to match one corner and take it to the shop with you. It is a surprisingly good guide to how much bend you need.

Track Options for Angled Runs

This is where a bay is won or lost. The track has to follow the angles and carry the fabric without sagging or twisting out of line.

Hand-bendable plastic track is the budget option and perfectly serviceable for light and medium curtains. You bend it by hand to match the angles, fix it to the ceiling or wall, and it is done. Corded versions save you reaching over furniture.

Aluminium track, bent to order or on site, is sturdier. If your curtains are interlined, or the bay is tall, choose this. It holds a heavy curtain without bowing, and corded versions make a deep bay far easier to live with.

Wave or ripplefold track has gliders set at fixed intervals so the fabric falls in a continuous, even wave. It suits a bay particularly well, because an unbroken wave draws the eye away from the angles. It needs exact measurements and a heading made to match the track spacing.

Poles are the awkward option. Bay poles come in sections joined at the corners, and rings cannot travel past a joint, so you end up with separate curtains on each face. That looks lovely when they are dressed open, but it means you cannot draw them as one. If you want the pole look, use it on the front face only, or have a curved pole made without joints.

Whichever you choose, put a bracket at every corner and keep the gaps between brackets modest once the fabric gets heavy. Ceiling-fixing inside the recess keeps brackets off your wallpaper and usually gives a straighter line to work to than the wall above the window.

Heading Styles That Suit a Bay

Headings change how much fabric you need and how much room the curtains occupy when they are open — and in a bay, room is the thing you do not have.

Pencil pleat is the most forgiving. It gathers to roughly twice its flat width, works with almost any track, and hides small measuring sins. Pinch pleat, double or triple, is more tailored and needs more fabric — around two and a half times the track width — but it hangs beautifully and keeps its shape for years. Wave is the cleanest, most contemporary choice. Goblet and eyelet are best kept for straight runs: eyelets need a pole, which brings you straight back to the corner problem.

The detail people miss is stack-back. A pleated curtain folds into a surprisingly fat bundle. On a bay with short returns that bundle has nowhere to go, and you can lose a third of your glass to fabric even when the curtains are open. Measure the space to the side of the window and be honest about it before you commit to a heading.

Fabric Weight, Lining and the Room Behind It

Light linens and cottons suit a shallow bay in a bright, unoverlooked room. They gather neatly and do not overwhelm a small space. Velvet, wool and chenille give a period bay the weight it deserves, but they need a strong track, generous bracketing, and space to sit when open.

Lining matters more than most people expect. A standard lining protects the face fabric, but if the bay is draughty or the room faces a busy road, thermal or blackout lining makes a noticeable difference to how the room feels. Interlining — a layer of wadding between fabric and lining — adds body, softens sound and stops curtains stirring in a draught. It also adds bulk, cost and effort when you come to hang them, so weigh that up first.

Two small tests before you order

Hold a sample against the glass in the evening with a lamp on inside. If you can see the pattern or colour clearly from outside, the fabric is too thin on its own for a bedroom. Then check your finished drop against the radiator: if the curtain will sit over a heat source, take it to just above the radiator top rather than trapping warmth behind it.

The Practical Order of Things

1. Decide the fixing line — recess ceiling or wall above the window.
2. Measure each face and the drop from that line. Write it all down.
3. Choose the track, allowing a bracket at every corner.
4. Pick a heading, then check stack-back space at both ends.
5. Match the fabric and lining to the room's light, draughts and noise.
6. Have curtains made, or buy ready-made panels with enough width to pleat.

Ready-made curtains are rarely a good fit for a bay, because they come as two straight panels sized for a flat window. Made-to-measure is the straightforward route. If you are handy with a sewing machine, buying extra width and joining panels to suit each face works well — just remember that every join adds bulk at the pleats. Hang them for a week before you trim the hem, too. Heavier fabrics drop as they settle, and a bay is a bad place to discover that a week late.

Photo: tiemaoanh / Pixabay