The city of São Luís, capital of Maranhão, located in northeastern Brazil, has an impressive collection of civil architecture, reminiscent of the eighteenth and nineteenth centuries. The architectural heritage was built during the golden period of the economy of Maranhão, during the second half of the eighteenth century and the nineteenth century, with a significant economic growth associated to the export of rice and cotton. This architectural legacy, concentrated in Praia Grande, Desterro, Mercês and Largo do Carmo, the oldest city’ neighborhoods, was classified by the federal government, and included in the World Heritage List, in December 1997. According to ICOMOS – International Council on Monuments and Sites – “the historic center of São Luís is an outstanding example of a Portuguese colonial city adapted to the equatorial South-America climate and has kept within the striking proportions and harmoniously integrated into the urban mesh the surrounding environment”. With approximately 5,600 buildings, constructed during three centuries, in the historic city center it is possible to find examples of various architectural styles: traditional Portuguese (buildings of the eighteenth and nineteenth centuries), neoclassical, eclectic, art deco, neoclassical and modern. Much of the architectural heritage is in poor state of conservation, presenting various defects affecting the structural system and architectural elements in the facades. This study aims to analyze the building system and defects of civil buildings constructed in the nineteenth century in São Luís do Maranhão, contributing to future rehabilitation programs.