Dee Verma
Hi Gary, not sure of the question, but i guess you are looking to replace the sealed units. depending on the type of frames i.e. pvc, aluminum or timber the process is very similar for all three but its the allowance you allow that matters. having said that, it all depends on the system. I have been measuring replacement sealed units for over 30 years and have been caught out a couple of times even with the experience i have. the sure way, is to remove the beads that hold the unit in and take the actual size. if that is a problem then measure the GLASS LINE that you see where the bead starts ie where you can see the surface of the silver or black spacer bar then add 23mm to the size you have measured for width and same for the height this should give you the required size. measure the thickness as well. if new windows its generally brick to brick sizes minus 10mm for width and 8mm for height. if in doubt get some one who's done it before as it can turn out to be a very expensive mistake. this method will not work for timber. for that you need the rebate size minus 6mm from overall sizes.
