1. Always measure the recess size (wall to wall measurement)

2. Always use a metal tape measure

3. Take measurements in millimeters

4. Specify width first and then height

5. Measure the window recess in 3 places and take the smallest measurement

6. Measure the height from the top of the window frame, down to the underside of the windowsill, in 3 places. Use the smallest measurement

Please note: PVC windows and doors must not be fitted tight into a brick opening - please allow 5mm (50cm) off each side and 5mm (50cm) off the top and bottom.