by Ellie Woolstenholmes
•
11 May 2021
The Tight size or Frame size is the size of the space in your window frame. To find the size of the glass, you need to take an amount off this measurement. If you were to get a piece of glass exactly the size of the frame, it would be a very snug fit or not fit at all and with the movement of the window frame, the glass would crack and double glazed units would break down. So, what do I need to do to find the glass size? If it is a single glazed window, take 5mm off each measurement. So, for example, if your Tight size was 542 x 798, your glass size would be 537 x 793. For a double glazed timber window, take 6mm off each measurement. So, for example, with the same Tight size as above, your glass size would be 536 x 792. For UPVC windows, it would be best to contact the manufacturer for their recommendation. The extra 2.5/3mm all around the glass allows for sufficient bedding material, air flow and also allows the glass to move within the frame. All of this will prolong the life of your glass. Unless asked to, we do not take anything off the measurements we receive so please do let us know if you are providing us with a Tight size!