Tertiary mathematics educators have been shifting towards an active learning approach to teaching. Many external factors support or hinder their transition towards evidence-based instructional practices, including, of recent international interest, the physical learning spaces. In this study in the U.S., I observed and interviewed instructors of introductory-level courses who taught in different types of classrooms during the same semester; in this paper, I focus on two of the instructors. A practicality theory lens, paired with qualitative coding methods that highlighted comparisons and tensions, revealed the challenges that instructors faced as they navigated the variability in learning spaces. Through analysis of classroom norms and pedagogical decisions and justifications, I found that particular resources, layouts, and features of classrooms influenced the feasibility of implementing active learning practices and the instructors' perceptions of an active learning approach in these spaces. This study presents implications for institutions wanting to support instructors as they transition to student-centered teaching approaches, especially instructors who must adapt between different types of learning spaces.