[Bruced]

The extension is complete so the each girls now have their 2sqm, or as near as dammit, and are busily de-grassing the area as I type. The old half of the run is covered (corrugated plastic) with a bark floor. I want to leave the new part uncovered to allow direct sunlight in should they want it for the few hours a day they are not free ranging. I want to use gravel in that part for easier drainage / cleaning but not sure what size to use - would 10mm be OK or something larger? The only larger stuff I found at B&Q was decorative stone, which might leave the ladies feeling like they are keeping up with the Jonese but seems pretty expensive. Also would about 2" be OK, or should I be aiming for a greater depth.

Thanks again for everyone's help!

[8doubles]

In my opinion a plain dirt floor is easier to de-poop than any type of shingle,bark or rubber and a dirt floor can be deep dug once in a while or the top taken off and composted (without any stones in) and a layer of fresh earth or compost added.
They may get a little bit muddy in winter but if they are not 'show chickens' why worry.

[andreadon]

I agree that dirt floor is easier than gravel to poo-pick, but it's worth having a small area with gravel for the benefit of the grit - 10mm stuff usually has smaller bits of grit in it that the chickens can dig around for and use for digestion.

You don't want your whole run covered in it, though, as you'll end up scooping up more gravel than poo!! 

[Spadefighter]

Find your local sand/gravel merchant who will sell it loose, way cheaper than b&q.