This article presents a contribution to the study of the architectural composition of Modest Residential Heritage built in the Historic Center of San Salvador in the late 19th and early 20th centuries. The objective is to identify patterns in the spatial organization of these dwellings, particularly the "casa patio" typology, which exhibits continuities from the colonial (virreinal) period to the republican era. Due to the lack of residential buildings from the virreinal period in San Salvador, four cases of virreinal houses from Antigua Guatemala, the capital of the Kingdom of Guatemala to which the province of San Salvador belonged, are analyzed. The methodology employed includes the comparison of the selected cases using Classification Schemes to graphically interpret three architectural elements: the patio with its corridors, the axis of access through the zaguanes (gateways), and the interior-exterior relationship. The results show that the patios play a fundamental role in the organization of spaces, and the architectural composition emphasizes order through the use of corridors. Additionally, the path from the entrance through the zaguanes to the chiflones (narrow passageways) connecting to other patios follows an angled route to avoid direct visibility between them. The comparative study reveals that the spatial organization of the four analyzed examples exhibits continuities in the distribution of spaces, potentially contributing to defining a typology of "Hispanic-American virreinal house" that is regionalized according to site-specific determinants. ILIA: Investigaciones Latinoamericanas en Ingeniería y Arquitectura, No. 01, 2024: 67-74.