I love the gradual/graded ramp!
Chickens are highly prone to respiratory infections. May I suggest that you stay away from powdery substances like DE, mite powders, baking soda, etc. We use a liquid organic OMRI spray called "Poultry Protector" for protection from mites/lice for both the coop crevices and on the chickens per instructions on label instead of powdery dusts.
Here is a link to the dangers of DE which has more warnings on it than a bottle of lye - if I have to use goggles and a breathing mask to use it then I don't want it anywhere around my chickens either: http://www.the-chicken-chick.com/2012/05/diatomaceous-earth-de-benefitrisk.html