confused about what to put on the run floor

I have been told that using bark from a garden center is no good for my hens and that wood chips are best.but i am confused on what type to use hardwood chips or softwood chips? can someone please help me out 

I use bark !  As long as it's play grade it's fine for hens 

play bark is better as it is generally free from any treatments.
wood chip will last longer, but as per a thread on the practical poultry website, it can run the risk of bringing in mites, either one will be better with the roof to the run covered to keep it dry, and easier to keep clean, i sprinkle with stanoslan f every week and rake it in, poop scoop what you can.

martyn

Ours are on slabs with cushion bed on top. they have a dirt area as well just for a change of texture. This is as well as free ranging.

We hired a big shredder last year as we had tonnes of pruning to do.  It created two huge piles which we have used in the run over the bare soil.  The girls loved spreading it out for us and we don't have any problems with flies or smells it all seems to compost down.

This winter I will probably scrape it all out, have a bonfire and burn the old stuff a put down some more.