This is for the size in Millimetres (mm) that you would like the window manufactured to. This size is to include any Cill and will be manufactured to tolerances of 2-3mm. Please ensure the sizes provided are not tight brickwork opening sizes as your new window may not fit, always allow a tolerance of about minus 10mm in the width and minus 10mm in the height. (Reduce size further if your opening is not square, out of level or has protruding bricks as your new window must be installed square, level and plumb).

Assumptions: The normal width for a side opening sash is 600mm, this is measured from the edge of the outer frame to the centre of the mullion (vertical bar). Exceptions: If the window divides into equal parts of less than 600mm (divided by mulions) then your side opener will be set at an equal division. Georgian bar, diamond and rectangular lead will be laid out according to our best practise.