Stone Chippings On A Flat Roof

[Khandro]

I have a ground floor extension on my house which has a flat bitumen roof, it is well waterproof but is black & has small puddles after rain & as it can be looked down on from that side of the house looks rather unsightly, so I am thinking of giving it a layer of small stones or gravel.

Does it need a coating of bitumen first before laying the stones or are they usually laid straight onto the roof surface?

It's about 15m 2

[Old_Geezer]

Don't know for sure but to me, it looks like mine were stuck to the roof originally but have become loose in the years since.

[SlackAlice]

Originally your flat roof should have installed with slight pitch to allow water to drain away. What ever you consider to do, think about the extra weight you will add to the roof structure by adding a layer of gravel/chippings.

[The Builder]

I'm assuming the roof has no chippings at present, and is just an asphalt covering?

"Ponding" is usually a sign that a flat roof is beginning to age.
But ... if this is a poured hot asphalt roof, then a few small puddles are obviously only an indication of an uneven surface.

Any idea if it's a "built-up" felt variety (3 layers of felt over a boarded surface), or poured with buckets of hot pitch?

[Zacs-Master]

If you do decide on chippings, maybe solar reflective ones would give an added benefit:
http://www.longrakespar.co.uk/products/roofing/solar-reflective

[Khandro]

Builder; It was made originally from layers of Bitumen & felt (I think) The architect at the time wanted to have it covered with some form of live plants, which my wife vetoed, so we have been left with a black roof which has always ponded a bit.
A local firm has just been & given all the joints a seal of some kind of grey catalysed material which, as the joints run crossways, i.e. not with the fall have made the ponding worse.
I'm told that ponding in itself isn't serious as long as the roof is water-tight which it is.
It now looks a bit of a dog's breakfast & covering it with pebbles seems to be a good idea visually.
I want to know if I can simply lay them on the roof or should they be held by a layer of a brushed on bitumen sealant.

[The Builder]

Chippings (when they used to be used - they're not any more), were usually bedded into a thin coating of bitumen.

If you're not likely to walk on them (and kick them around), then I would just spread them dry.

A single layer of 10mm chips would add around 250kg to the load on the roof. SlackAlice makes a good point about this.

However, I would take a stab and say that, spread over 15 sq. m., this is an acceptable "imposed load".

For a pukka job, i.e. more expensive, I would have someone pour a layer of hot pitch all over to level it all up.

[woofgang]

Builder, as a sidelight on theis discussion, what do you think if the new rubber sheet roofing?

[The Builder]

Woofters, it's the way to go.

I've used it on my garage.

EPDM

[Khandro]

Thanks Builder.
& Zacs, I'll get some light coloured smooth stones as in your link.

[woofgang]

yes I just had my old shed done with it.