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Roller Insect Screens - Measuring a Window with an Opening Pane next to a Fixed Pane


If you are ordering a roller insect screen to install at a window that is made up of an opening pane next to a fixed pane, then you may not need to cover the whole window with a fly screen. Instead, you can cover just the opening pane. 

Why cover only the opening pane?

This has cost advantages because you only need to order a screen to cover part of the overall window - so the screen should be smaller and lower cost.

Why cover the whole window?

Covering only one panel, rather than the whole window, usually requires the screen to be fixed to the window frame itself. If you wish to avoid fixing directly to the window frame. Then you may still wish to order a screen to cover the full window and side/top fix the screen into the recess.

How to Measure

If you decide only to cover the opening pane of the window, you will need to order the screen at 'blind size'. This means that we'll make the screen to the width and drop that you provide, including the cassette and side channels.

You should consider the following dimensions:

  • Side Channels: Each side channel is 30mm wide. 

  • Cassette: The cassette is 51mm high

The table below summarises the measurements you should take and the adjustments that you should make to these measurements, depending on how you wish to fix the cassette into place.

How to measure a roller insect screen to cover a full height opening panel next to a fixed panel

We'll talk through these measurements and adjustments in more detail below using some example measurements:

Width Measurement

Firstly, for the width, open the opening pane of the window. Measure the width of the opening itself.

As an example, for simple maths, let’s say this is 1000m (1 metre) wide. 

Since each side channel is 30mm wide, you would need to add at least 60mm to the width of the opening, so that the side channels are positioned on either side of the opening.

Example Blind Width 1060mm

You may want the screen to be slightly wider so that the side channels aren’t flush with the opening. How much you can add to each side will depend on how much space you have to the left and right of the opening. This might be restricted by the width of the mullion where the side channels will be fixed, or by the distance from the edge of the opening to the recess edge.

Let’s say we want to (and have space to) add on a further 5mm on each side, to allow a little bit of space between the opening and the side channels. 

Example Blind Width 1070mm.

Drop Measurement

Now for the drop measurement. If the window is set in a recess and the window has a sill, then you can measure the recess height. 

For simple maths, in our example, let’s say this recess height is 1000mm (1 metre). 

We'd usually suggest using a top-fix bracket to fix the cassette into the top of the recess. To allow for this bracket and a small recess deduction, you would deduct 6mm from this size.

Example Blind drop = 994mm

In summary

Blind Width: Opening width PLUS 60mm (or more if you prefer and have space)

Blind Drop: Recess drop LESS 6mm

Giving a blind size as follows:

  • Blind Width 1060mm
  • Blind Drop 996mm

For other options, you will need to select:

  • My Sizes are: Blind Size
  • Cassette Fixing: Top Fix Bracket
  • Side Channels: Face Fix (using screws)
  • Do you have a window sill: Yes, screen pulls to sill.

Other Fixing Options - Face Fixing the Cassette:

If you want to face-fix the cassette, then deduct 15mm from the recess height.

Also, select Cassette Fixing: Face Fix Bracket

For our example of a 1000mm recess height, this means:

Example Blind Drop: 985mm.

Other Fixing Options - No Cassette Bracket

If you don’t wish to use a bracket at the top, this is fine also, since the cassette will be held in position by the top of the recess and the screen will also be fixed in several places in the side channels. You can simply deduct 2mm from the height.

Also select Cassette Fixing: Top Fixing. 

In this instance, you would receive a top fix bracket, but you would not need to use it.

Example Blind Drop: 998mm.

Need More Support? 

If you are uncertain about your measurements for this application, our friendly team are here to help at [email protected]. Feel free to send us a photo of the window you are covering and we will provide advice on how best to measure. 


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