Though this looks good, and as I said before, very similar to my Mums, I would seriously consider a cover over the run.
We have had heavy rain today for the first time since ours was installed. I went up to a sea of mud with four hens paddling in it! Poor Martha Cecilia, who is very short legged, had mud on her stomach feathers. I have put a sheet of Onduline/Corrugated bitumen, cut to fit & screwed it over the roof of the run. I added a thin strip of wood at the coop end between the onduline and the run roof to create a slight fall so the rain drains away from the coop. I used the rubber caps that you can get to protect the screws from the wet and it was fairly easy to do.
I am considering putting Easichick chippings in the run straight onto the soil to absorb excess moisture and dry it out while also giving the hens something loose to scratch around in. Not sure about this though so if anyone has any advice.