This Old House says, “Even if it’s currently cold concrete and crammed with boxes of off-season duds, the lowest floor of your home probably has loads of potential. Treat it just as you would any of the rooms above ground, and it might just become the most popular spot in the house—for a lot less cash than adding on. Here’s their step-by-step bottom-line advice for turning this underutilized space into a place you’ll be eager to spend time in.