This essay develops the concept of material inertia, a lens for studying artifacts of material and spatial rhetorics with a focus on long durations. The essay uses the case study of the DeWitt Clinton High School building, constructed in 1906 in New York City and still in use at CUNY John Jay College, to demonstrate how friction between the building’s design and use is exacerbated over decades. The essay argues for reading long-lived spaces via material inertia to understand the rhetorical force of non-human actors across time, and calls for scholarship in material rhetorics to take specifically durational approaches.