Secondary Double Glazing  - Measuring

To ensure the perfect fit for your DIY secondary double glazing you need to take accurate measurements.

When you are measuring you need to take into account the following:

• make tolerance deductions
• make adjustments for any out of square apertures
• use the correct glass particularly in situations where safety is important
• line up where the DIY secondary glazing panels join with the primary window panels   

For advice on whether to measure for face fixing or reveal fixing plese visit our section on how to fit.

If at this stage all you want is a quotation then all we will need from you are the approximate height & width (to within 30mm), the  window type and the glass required.

You must take accurate measurements to ensure that your DIY secondary glazing will fit correctly.

There are some factors that need to be taken into account:

• you must make an adjustment to your sizes to allow tolerance during fitting.
• it is likely that your window opening will be out of square - most are (blame the builders!)
• you need to make sure you fit the correct glass - particularly where safety is involved.
• you will need to line up the point where the DIY secondary double glazing panels meet with the corresponding point on the existing window.

Don't worry - it's not that complicated.

If at this stage all you want is a quotation then you will only need rough sizes (within 30-40mm), the window design and the glass type at this stage. 

Get a no-obligation secondary glazing quotation

It is likely that you window opening will not be perfectly square or level - very few are. You should take comparative measurements at various points on your existing window or window reveal and take the smallest measurement.

The following diagram is an extreme example of a badly out-of-square window the dotted line shows where the tightest points are for DIY secondary double glazing to fit.

Take measurements for your DIY secondary glazing in metric format and state all sizes in millimetres, Please always give the width first to avoid confusion.

• measure from wall B to Wall E and then deduct 10mm for tolerance (ie 2000mm less 10mm = 1990mm).
• measure from wall A to Wall E and then deduct 10mm for tolerance (ie 1200mm less 10mm = 1190mm).
• measure from wall B to the centre of mullion C and deduct 5mm (ie 600mm less 10mm = 590mm).
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• measure from wall D to Wall C and then deduct 10mm for tolerance (ie 1000mm less 10mm = 990mm).
• measure from wall A to Wall C and then deduct 10mm for tolerance (ie 2000mm less 10mm = 1990mm).
• measure from wall A to the centre of transom B and deduct 5mm (ie 1000mm less 10mm = 990mm).

Which glass you need for your DIY secondary double glazing will depend on whether you are trying to reduce heat loss, stop draughts or cut out noise.

Please refer to glass types to see the options available and make your choice. 

You  ust comply with Building Regulations for safety glazing which must be used in the following situations:

• if any part of the glazed panel comes within 800mm of the floor
• if any part of the glazing over a door comes within 1500mm of the floor
• if any glass in a window within 300mm of a door comes within 1500mm of the floor 
• anywhere that presents a fdanger to someone accidentally falling against glass ie windows next to a bath or on stairs, landings and half landings.

See below for guidance:

Measuring bays are a bit more complicated but are not beyond the capabilities of a DIY secondary double glazing installer.

We suggest that for the purpose of getting a quotation you provide us with rough sizes (within 30mm - 40mm) and we will provide further instructions for how to measure accurately once you are in a position to proceed to order.

Get a no-obligation secondary double glazing quotation