Realistically, I would guess closer to 8-10 feet. It's a freestanding deck in my back yard next to the pool. There'd be space along the railings they could grow laterally though, if that makes a difference.
I don't have any real place in my yard to build a full-sized trellis, and I don't think my neighborhood bylaws would allow it anyway. Since I have this giant ass wooden deck that I want to soften up anyway, I thought hops vines might be viable. It's a very sturdy structure, so assuming the vines won't shatter the wood like ivy then I think it'd be safe enough.
I've also got to find some sorts of vines to grow along the chainlink fence as well. I hate the way that stuff looks.
edit: Haha, okay okay I'll find a way to grow hops. Don't kill me
edit edit: Okay next question. How much light is required? The house would shade that area for part of the day, but it stays fairly sunny until evening when the sun falls behind the treeline.