Run floor?

My hubby is going to build me a run, it is going to go down the side of our garage which is about 17ft by 6ft.

I have been toying with plans for it.  We have decided that we will make the back wall of the run out of wood which will also double as a fencing panel facing onto our front garden if that makes sense.

I had originally drawn the run about 1.5ft starting inside the fence panel so as to be able to get behind to clear out any dirt/leaves etc but then you obviously lose run space.

Problem with having the run doubling as the fence panel is that I cannot stick a wire skirt on the other side of it to prevent foxes digging.

So, does anyone think foxes would dig under a wooden panel?  I assume they work on smell rather than sight so I didn't think it'd stop them would it?

Also, second option, just to cover entire bottom of the run in weldmesh but I wasn't sure if the chickens would like that as it messes up scratching and dustbathing doesn't it?  I did think I could maybe put a tray/plant pot or something with stuff in to dustbathe?

And last question, what would you put on the floor of the run if anything?  I.e. woodchips etc??

Just wondered what everyone else thought?

I would as tode says bury weld mesh skirt on the inside of the run as when/if a fox tries to dig under he/she will come across it as a barrier. 
No you do not need weld mesh all on the floor.

I would be more concerned that a fox could jump over your fence panel and they can. May I suggest a single strand of electric fence wire on the top of the fence and a single strand of earth wire.  This will ensure a fox would get a belt from the wire even with all paws of the floor.