Traditional towns in Portugal and Brazil have evolved a finely tuned coordination between, on the one hand, modular dimensions for street widths and lot sizes, and on the other, a typology of room shapes and layouts within houses. Despite being well documented in urban history, this coordination was in the last century often interpreted as contingent, a result of the limited material means of pre-industrial societies. But the continued application and gradual adaptation of these urban and architectural patterns through periods of industrialization and economic development suggests that they respond both to enduring housing requirements and to piecemeal urban growth. This article surveys the persistence of urban and architectural patterns up to the early 20th century, showing their resilience in addressing modern housing and urbanization requirements.