I wanna try and better qualify what I mentioned earlier. Mothballs are naphthalene, which is pretty vile stuff that you don't want in your soil, water, kids hands or pets mouths. I've no experience with it keeping snakes away, but it is an old favorite remedy, along with sulfur. The sulfur solution is only good till it rains, so keep that in mind, as well as where all of that excess sulfur is gonna end up if you use it long term. There's a product out called "Snake Away" that I believe is a combination of the two.
On the non-chemical front, I've also heard of people using everything from ceramic eggs and golf balls, to burnt out light bulbs, as a decoy/trap. If you're trying to eliminate a threat that isn't likely to stop coming around to eat your eggs or chicks on its own, I would say try all of the non-chemical approaches first, along with securing the house, and then maybe try the sulfur. As for the rats, mice, snake circle of life - you can help keep the rodent interest low with good housekeeping, but there are a lot of snakes that thrive on rodents, and their sense of smell I guess it is in tracking them is pretty crazy, so if one comes, it's only a matter of time until the other follows.
Don't know your other particulars, but we had great success in the past protecting our ponds with electric 'coon fencing. It was about 30" tall and I plan on using it around our runs and tractors to keep the foxes from diggin'. Worked before keeping the cats and possums away from our fish, and I'm guessing snakes too, since we used to see them all of the time near the ponds and after the fencing we never saw them again. Just anecdotal but it might be worth a try if the other ideas are unattractive or don't work for ya.
Other than the wire funnel traps, I've also read of folks using the plastic bird netting. One edge is buried a few inches into the soil and the rest is kind of bunched up and supported in a mass maybe hanging over a wire or line about two feet above the ground. Apparently some snakes will get tangled up in it. You could also try setting a couple of the large glue traps under cover, and staking them to the ground real good. Glue trap catches rat/mouse, whose scent and body heat attracts Mr. snake, and even Mr. snake isn't likely to get free of one of those big sticky traps I wouldn't think. Other than that, Seal up that hen house real good 'cuz generally once they have discovered a food source they will keep coming back as long as the supply holds out. You could also add some smaller opening hardware cloth, but rat snakes in particular are very adept climbers, so bear that in mind as well.
Last but not least, Ruger makes a nifty .22 semi-auto pistol, and snake shot is cheaper than the $5 a gallon gas used to relocate. Also works good on rats and scarin' the odd uninvited animal guest off at distance.