Use Hardware Cloth
Wherever you would use chicken wire, such as window areas for ventilation, around the bottom, or to make the run, use hardware cloth instead. Some raccoons will just rip open chicken wire and enter at will. Hardware cloth (the finer mesh the better) is more expensive but much more of a deterrent.
Protect Them From Burrowing Animals
Bury hardware cloth 12 inches down all around the coop to protect from rodents and other burrowing animals.
Make a Solid Floor
A solid floor will keep any burrowing invaders like rats or raccoons from getting in. It will take them more time to chew through a solid floor. Especially in conjunction with hardware cloth, this can be an effective approach.
Leave a Space for Your Cats to Crawl Underneath
If you have cats, elevate your coop floor about a foot off the ground. The cats will crawl under and eliminate any rodents or other small, annoying visitors.
Surround the Bottom with a Strand of Electric Wire
Another option for securing the bottom of the coop is to use a single electric wire near the ground so that a predator such as a rat or a raccoon will get its nose shocked when it tries to burrow under.
Surround the Perimeter with Electric Net Fencing
This can be used in addition to basic precautions such as a coop floor and hardware cloth. Tiny invaders like mice may be able to sneak under without a shock, since the very bottom string doesn’t always touch the ground. But anything like a raccoon that would climb a fence will get zapped and discouraged. The closer the electric net spacing, the more effective it is against smaller predators.
Protect From Above
Secure the top of the chicken run with aviary netting or deer netting. This will help defend against predators like chicken hawks, and it will keep wild birds from mingling with your chickens. Predator-proof the run. Bury the chicken wire or hardware cloth 12 inches deep all along the run to add an additional barrier against burrowing predators.
Get a Livestock Guardian Dog or Two
Dogs are really useful on a farm. With a dog outside with your hens, nothing will dare approach. Urine and feces smell will keep predators at bay at night as well. However, some dogs will go after chickens themselves, so you need to train them not to chase and “play” with them. An electric training collar can be an invaluable tool if your dog is bred to go after chickens (like a retriever).