Is it up on a rooftop or housetop?

Well, sweetheart, technically, both "rooftop" and "housetop" refer to the top of a building. However, "rooftop" is more commonly used nowadays and has a bit more pizzazz to it. So if you want to sound hip and trendy, go with "rooftop." But hey, if you're feeling old school, "housetop" still gets the job done.