How long before eggs are fertile, when adding a roo?

[GhostRider65]

I have had my Hens and roos, separate for about a month now, I want to hatch some Delaware chicks, EE's and Wyandottes after I add my Roosters to the breeding pen along with 4 girls, how long must I wait for fertile eggs? I would think that he must breed them a few days before the eggs are fertile, but I'm a newbie so what do I know, and how long should I keep them together, 4 hens is not very many for 1 rooster, and I don't want him to pull out all there back and head feathers? or hurt them........... BTW he is a young roo not a year until late May.
Does anyone keep there roosters separate? and how best to intro them to the hens? they do know each other and can chat through the fence.....................Thanks much Kim

 

[Fred's Hens]

A rooster in with a half dozen hens, needs a week or 10 days to make the complete rounds. He'll usually get to them all within that time frame. Some hens refuse his advances and he has to earn their respect. Some hens are very compliant, so it all depends.

A hen is "working" on an egg three days before she lays it. So, even if she if successfully mounted/mated, it takes a few days before her eggs are fertile.