Originally your flat roof should have installed with slight pitch to allow water to drain away.
Why put chippings on a flat roof.
There are different types and weights of gravel used on flat roofs for these purposes.
Two common problems faced by owners of flat roofed properties are the build up of moss or silt and the free movement of improperly secured gravel chippings or pea shingle from the surface.
However the chippings can move around or conceal defects in the roof and should not be walked on as they may puncture the membrane.
Chippings can be used provide a ballast layer to help hold down the roof surface in exposed locations.
Chippings should only be used on roofs at less than 10 as complete adhesion at steeper pitched is not possible.
These issues are not something that you should encounter in the natural lifespan of your flat roof so should be taken as a sign warranting investigation.
10 08 fri 01st nov 2019.
The chips act as a barrier between non solar reflective felt and the sun basically help prolong its life span of the felt if its green mineral on your new roof you will not have to chip it as the minerals are solar reflective.