Once you know the required length of the rafter boards (see below), purchase lumber that is at least a foot longer, plus the length of your overhang. With that being said, the average residence’s roof (3,000 square feet or less) can be replaced in two days—on day one, you rip up the roof, and on day two you install the new roof. A metal roof will reduce cooling costs by reflecting heat and last 50 to 70 years. Armed with a basic understanding of the anatomy of a metal roof, along with a few tips, you can install one yourself in just a few days. With its sleek, modern look, metal panel roofing was our first choice for the Getaway.