estalagens were groups of tiny houses built next to one another, while casas-de-cômodos were larger houses internally subdivided so that they could be rented to many occupants. 

when these estalagens and casas-de-comodos were enclosed by a perimeter wall, they would become a Cortiço - technically meaning 'beehive' or 'patio,' the term 'Cortiço' was used to generally refer to a collective housing arrangement based on shared rooms, corridors, water tanks, and bathrooms, typically built very near places of employment or factories.

the building of Cortiços was an extremely lucrative business in 19th-century rio, leading to the proliferation of these kind of housing arrangements - the multiplication of Cortiços, all subject to poor ventilation, overcrowding, insufficient illumination, and poor hygiene resulted in the spreading of diseases such as colera, smallpox, and yellow fever.