Slender House upends the core constraint of the “too narrow to build on” urban infill lot. By insisting on qualities necessary for dignified dwellings – light, air, thermal comfort, affordability, accommodation – the project shows that the narrow lot is, in fact, plenty wide. By rejecting the presumption of wall-to-wall infill strategies, Slender House offers a new, emblematic row house typology within the New York borough neighborhoods. The project proposes a three-step process that is replicable across many infill lot typologies. First, optimize building form within the allowable constructible volume (lot length x lot depth x FAR height + entitlement allowances) by first maximizing the capture of natural light and beneficial airflow, and second, by employing conventional construction methods and materials for broad application. Second, create generous interiors and new models of shared/private amenities throughout the entire building and site. Finally, weave into the neighborhood and immediate block context.