gravel on roof?

[sparky (sfd)]

i have helped a friend recently put up some new guttering on his extension its about 10 years old and was done before he moved in. but i noticed it had some type of gravel on there does this offer some sort of protection to the felt underneath

 

[GwaiLo]

Yes,
Roofing felts are degraded mostly by the effects of UV light, which brings about chemical changes which I am loathe to go into.

A layer of chippings helps prevent the UV light from being absobed by the felt and so prolongs its life.

 

[breezer]

it is (i believe) supposed to break down the force of the rain, but more importantly stop the suns U.V rays from breaking down the roof "material" too quick

I have seen cheap pondliners that have not been installed properly, and when exposed to the sun for a few years the best way to describe them is "giant black cornflakes" this is becasue the suns UV rays quite literaly break down the material

 

[sparky (sfd)]

cherrs just that ive never seen it before.