Surveying Flat Windows

Take measurement of the width,height and diagonals as shown in Fig 1. The smallest measurement taken determines the tight overall width & height sizes.

The deductions shown in the table below. should then be made all round the perimeter to allow for expansion and contraction, dependant on the size and finish of the new frames. The sizes left are the manufacturing sizes for the new frames.

Determine if projecting sub-cills are to be fitted and where included ensure that a minimum projection of 25mm is provided beyond the structure.

Measure internal reveal sizes and compare with external opening sizes to ensure that opening lights are not impeded; this is important for inward opening doors and tilt & turn windows in particular. The thickness of external rendering should be checked for clearance of outward opening lights.

The survey should also determine the installation method to be used (e.g. through the frame fixing or with lugs) and ensure compliance with system designer and industry recommendations.