Venetian Blinds Bay Window Fitting: Three Blinds, One Line of Slats

A venetian blinds bay window job looks right when the slats run as one unbroken line across all three blinds, and that only happens if the drops match and the headrails sit at the same height. Everything else is detail. Get those two wrong and you see it from the doorway every day.

This is the error people find after fitting, when the blinds are up, the brackets are in and the holes are drilled. So venetian blinds bay window work is worth an hour of thought before you order.

Key Takeaways

• One line of slats or nothing. A venetian blinds bay window run reads as one window only when the slats line up across the joins.

• Headrail height comes first. A few millimetres between brackets throws the whole run out of step.

• Match the drops deliberately. Order all three to one drop even where the openings differ slightly.

• Every bay has a corner wedge. Two blinds meeting at an angle leave a gap, and there are three ways to handle it.

• Angled bays need the angle. A square bay is three rectangles. A 45 degree bay is not.

Why Three Blinds Can Look Wrong Together

A bay is one window to your eye and three windows to a tape measure. Nothing bends round a corner, so you are fitting three separate products and asking them to behave as one.

The tilt gives the game away. Close the slats on a venetian blinds bay window run and each slat should sit level with its neighbours either side, so the closed face reads as one continuous surface. Hang one blind ten millimetres low and every slat in it is ten millimetres out of step, which shows as a stripe down the join. Open, you might not notice. Closed, it is all you see.

Slat width is the second giveaway. Across the venetian blinds bay window options the slat sizes vary by range, and mixing 25 mm on the short returns with 50 mm on the centre pane guarantees the lines never meet. Pick one width for all three.

Venetian Blinds Bay Window Drops and Headrail Heights

Start at the top. Mark one level line across the whole bay, from the outside edge of the left return to the outside edge of the right, using a long spirit level or a laser. That line is where every venetian blinds bay window headrail goes, whatever the reveals do.

Bay reveals are rarely level with each other. Houses move, lintels sag, plaster was never flat, and in an older property 5 or 10 mm of difference between the centre pane and the returns is common. Measure each opening separately and you inherit all of it.

Drops follow the same rule: decide one finished height for the bottom rail and order all three to reach it. Where a sill is uneven, finish slightly above the lowest point rather than chasing each sill. A uniform centimetre of gap looks deliberate. Three different gaps look like a mistake.

Order venetian blinds with that single drop written on all three lines of the order rather than calculated separately. Made to measure venetian blinds are cut to what you send, so a transcription slip here becomes permanent.

The Corner Wedge Nobody Mentions

Here is what nobody tells you before the blinds arrive. Two flat blinds meeting at a bay corner cannot close that corner. The headrails are rigid, they have end caps, the brackets need room, and where the panes meet at an angle there is a wedge of glass no flat blind covers. On an angled bay it is narrow at the top and wider at the bottom, and it is permanent.

Three ways to deal with it, all of them compromises.

Accept it. On a shallow bay the wedge is thin, and with the slats closed it reads as a vertical line most people stop seeing within a week. This costs nothing and it is what most installations do.

Overlap. Order the centre blind wider so it runs past the corner and sits in front of the return. The gap is covered from inside the room, but one blind now overlaps another, so the tilt rods foul each other if you close them hard.

Change product at the corner. A shutter blinds bay window installation deals with the wedge properly, because the frame is built to the angle rather than hung flat across it. Within venetian blinds bay window fitting, the wedge is simply a given.

Measuring an Angled Bay Against a Square One

A square bay is three rectangles meeting at right angles. Measure width and drop for each opening inside the recess at top, middle and bottom, and use the narrowest figure. The corners are 90 degrees, so the headrails stop short of each other and the wedge stays small.

An angled bay is harder. The returns meet the centre pane at something near 45 degrees, so each headrail has to stop before the corner or collide with its neighbour. Measure each pane along the face of the glass, work out the room the bracket and end cap need, and deduct it. If unsure, deduct a little more: a blind 10 mm narrow looks fine, a blind 5 mm wide does not fit at all.

Take the angle while you are up the ladder. Hold a piece of card into the corner, trace the angle and keep it, because a bay that looks like 45 degrees is often 40 or 50 and the deductions change with it.

Wooden slats behave the same way but weigh more, so a long centre blind sags over time and a made to measure wooden blinds order on a wide bay is worth splitting into two blinds on one headrail. Where drilling the reveal is not an option, perfect fit blinds clip into the glazing bead, keeping each blind inside its own pane and hiding the wedge behind the frame.

Measure the bay as one window, order bay window blinds as three, and keep the headrail line straight. That is the whole job.

Frequently asked questions

How do you measure a bay window for blinds?

Treat it as one window measured in three parts. Mark a single level line across the full bay for the headrails, then measure each pane at top, middle and bottom and use the narrowest width. Take one drop figure for all three blinds, finishing above the lowest point of the sill. On an angled bay, deduct enough width at each corner for the brackets and end caps to clear their neighbours.

How do you fit blinds in a bay window?

Fix every bracket to one marked level line before you hang anything, working from the centre pane outwards so any error lands on the returns rather than in the middle of the view. Hang the centre blind first, check the slats sit level, then add each return and sight along the closed slats from the side of the room. Adjust before the final tightening, not after.

How do you measure for venetian blinds?

For an inside fit, measure the recess width at three heights and the drop at three points, then give the narrowest width and the longest drop and let the supplier take their standard deduction. For an outside fit, measure the area you want covered and add an overlap at each side and above. Bay window venetian blinds use the same method per pane, with one shared drop across the run.