Guide to Parliament and Projection Hinges -INFO36
Projection hinges are drilled with holes towards the edge of a broad hinge leaf, enabling the hinge to clear obstructions when fully open beyond 90 degrees.
When a door is to be opened beyond 90 degrees the width of a hinge can be calculated as follows:
It is recommended that the backset should not be less than 12mm (14mm if using an intumescent strip).
Door thickness plus inset (normally 3.2mm) less backset.
Double this and add clearance required.
