Young adult (YA) librarianship has received growing attention in the library literature over the past several years. However, the majority of writing on this topic has focused on the services provided rather than on the physical spaces where these services take place. As U.S. public libraries are evolving to meet users' changing needs, we are in need of new design principles that reflect how users are actually using and interacting with their library spaces. Physical design elements have a large impact on how welcoming and comfortable the library feels, making user-centered design a crucial consideration in serving teens.