How to Measure a Box 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 in the corners 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. Note down the depth of the deepest window handle within your bay.

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

You’ll then need to measure the depth of your recess opening, as well as the depth of the windowsill. Note these measurements down.

You should now have:

• Depth of the Windowsill
• Depth of the Recess
• Distance from the Front of the Window to the Front of the Shutter (from the table above)

You can then compare both your windowsill and recess depth with the ‘Distance from the Front of the Window to the Front of the Shutter’ measurement.

If either of these depths is more than 30mm smaller than this distance from the table above then please contact us for guidance before measuring.

For example: if the table above gives a measurement of 120mm, your windowsill and recess must be at least 90mm deep. If either measurement is less than 90mm, please contact us for guidance on measuring your specific window.

When measuring the width of your box bay, it’s important to measure the width of each window section 3 times (across the top, middle, and bottom). For each section, note down the smallest width measurement.

You’ll need to then refer back to the “Distance from the Front of the Window to the Front of the Shutter” measurement from the previous step. This measurement should be deducted from your left and right window width measurements. For the central window, you should deduct this measurement twice. This will ensure the shutter frames meet correctly at the bay window corners.

For example: if the “Distance from the Front of the Window to the Front of the Shutter” measurement is 120mm, then you would deduct 120mm from the left and right window measurements, and 240mm from the central window measurement.

Once you’ve made these deductions, you should then deduct a further 3mm from each of your width measurements.

For the height of the shutters, you should measure each window’s drop 3 times (left, centre & right). If the centre window is particularly wide, you can take an additional few measurements.

Note down the smallest drop size across your windows. You’ll then need to deduct 5mm from this measurement.

Important: All shutters should be ordered to the same drop to create a consistent finish across the bay.

Please Note: This measuring guidance is only suitable for recessed bays that have their own ceiling as in the image shown here. If your bay window is not recessed, e.g. the height of the ceiling of the bay is the same as the rest of the room and there is wall space above the windows, contact us for guidance on how to measure.

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.