Add-on’s Guide

ADD-ONS. 10mm 20mm or 50mm available.

Generally, an add-on is used if the inside reveals of your house are smaller than the outside measurement of either the rendering or the brickwork. In this particular example, you would take your inside measurements then take your outside measurements if the outside measurement is greater than 20mm then it may be advisable to start adding add-ons were required either left and right or top or bottom.
You may also need an add-on if you require trickle vents on a sliding door or bifold door in this case you would need a 50mm add-on to the head and the trickle vents will be fitted to the add-on.
When considering add-ons always give the width and height of the overall frame, including add-ons.
If unsure of this procedure, please consult with a professional window fitter.