How to Measure an Angled Bay for Shutters

L Frames are the recommended frame style for all bay window installations. They sit neatly within the window recess, helping maximise the available space while allowing multiple shutters to fit together accurately around the angles of the bay.

Using an L Frame provides a clean, streamlined finish and ensures there is sufficient clearance for adjoining shutter panels to open and operate correctly.

Z Frames wrap around the face of the recess, which can reduce the available space between windows in a bay and make it more difficult to achieve the correct panel clearances. For this reason, L Frames provide the best fit and operation for almost all bay window installations.

Measure the Depth of your Window Handle

First, you’ll need to check how much clearance you require by measuring the depth of your window handle. Measure from the window frame out to the edge of your handle and note down how far it protrudes.

Please Note: If your windows open inwards, you’ll need to ensure you have enough clearance to ensure they don’t hit off the louvres of the shutter. To check this, measure the depth when the window is open.

Mark the Clearance Required

Take 2 A4 pieces of paper and mark these with 2 lines going across the page. The position of the lines on the paper should be as below:

63mm/76mm louvres:

• Line 1= (window handle depth) + 10mm
• Line 2 = (window handle depth) + 70mm

89mm louvres

• Line 1 = (window handle depth) + 20mm
• Line 2 = (window handle depth) + 80mm

Once you’ve drawn your lines, below ‘Line 2’ mark both pieces of paper with an ‘X’. This will indicate the side of the paper you should have up against the window frame. Mark the papers as ‘Paper 1’ and ‘Paper 2’ as this will become helpful later in the measuring process.

Mark up your Recess

1. Take your first piece of paper and place it on the windowsill in front of your left window & then take the second paper and place this in front of the middle window.

2. With the pieces of paper butted up against the window frame, gently move them across until both of their Line 1’s meet. Using a pencil, mark this meeting point on your windowsill.

3. Repeat this process for the window on right and again, mark where both Line 1’s meet on the sill.

4. You now have the measure points where the windows meet each other.

1. Position Paper 1 so that it butts up against the windowsill in front of the far-left shutter.
2. Move Paper 1 across to the left until it touches the recess.
3. Mark the point where ‘Line 1’ on the paper meets the recess wall.
4. Repeat this process for the right window.

1. On Paper 1, fold the lower right corner of the page. This fold should start from the line marked Line 2 and should be folded back to the middle of the page.
2. Repeat this on Page 2, but at the left hand corner.
3. With Paper 1 pushed up against the window frame, move it across until ‘Line 2’ touches the wall.
4. With ‘Line 2’ touching the wall, mark on the sill at the edge of ‘Line 1’
5. Repeat this process on the right of the bay using ‘Paper 2’

1. With all of the measure points now marked on the recess, use these to measure each window and note them down.
2. Deduct 3mm from the left and right window measurements. The central window doesn’t require any deductions.

1. To work out the height of the shutters, measure from the windowsill up to the top of the ceiling recess.
2. Do this 3 times on each window within the bay, noting down each measurement.
3. When you have measured each height, identify the smallest measurement and take 5mm off that measurement.
4. Order every shutter at this height.

Mid rails are generally placed halfway up the blind, or where you find a transom (a horizontal beam separating one pane of glass from the next on your window). For Bay Windows, we ask that you use the same mid-rail height for all shutters.

If your shutter requires a mid-rail, you must provide details of where you want this.

To get your mid rail height measurement, simply measure from the bottom of where the shutter frame will be fixed, up to the centre of where you want the mid-rail to be.

Please Note: Your mid rail height must be at least 400mm from both the top and bottom edges of the shutter. For example, if your drop is 1000mm, your mid rail height must be between 400-600mm.

Simply measure from your windowsill up to the centre of where you wish the panels to split into the top/bottom tiers and enter this measurement as your ‘divide height’.

When installing Tier on Tier shutters in a bay window, you should order all shutters with the same divide height.