True Mr. Nagolbud...Cats and other stalking creatures are opportunists. I can't watch over the Gals during the day but when most predators prowl at night, my hens are safe in my coop.
The two tings I did when building my coop were to use cage wire with small holes. Knowing some predators can dig under the framework I made a floor of wire completely affixed to the lower frame; end to end, side to side. The coop lays over the frame and it is safe from outside predators entering from underground or above ground. I also put 5-6 inches of sand/topsoil mix as a floor over the screening.
My son did one better and he has an electric fence barrier surrounding the posterior from the ground up. He has snakes, moles to raccoons, and the electric fencing did the trick. His unit is powered by a battery (solar power) and it is always active. His birds are not hurt by the fencing material.