Backyard Fowl Keepers

I've kept mine behind a 5' fence for years with no issues. As long as they have enough to do and no major predators lurking, they probably won't bother testing it.

Consider how much space they have. If they feel cramped, they'll be more likely to try flying over. More room = less motivation to escape!

If you have breeds like Leghorns or Easter Eggers, they might fly over 5'. If they do, you could always add a topper or some netting later.