PurposeThis paper aims to examine the effects of transformations of the levels of visual and functional permeability and the types of uses on the ground floors of buildings on the perception of security and the occurrence of residential burglary, theft in residence, pedestrian mugging, vehicle robbery, vehicle theft and theft of items inside a vehicle on selected blocks.Design/methodology/approachNine blocks divided into three groups were selected in Capão da Canoa, a Brazilian city that has been undergoing morphological transformations, including the replacement of buildings with residences and shops on the ground floor, with doors and windows facing the street, by buildings with a predominance of garage doors and blind walls on the ground floors. Data were collected through the application of questionnaires and interviews.FindingsThe results reveal, for example, that perception of greater security is related to the blocks with a greater number of functional and visual connections between the ground floor interfaces of the buildings and the open public spaces. In addition, the night period records the higher number of criminal occurrences, even on blocks with higher rates of visual and functional connections between the ground floor interfaces and the public open space and higher rates of residential and commercial uses on the ground floor of the buildings.Originality/valueIt is expected that the results of this paper will allow for greater knowledge and the revision of many urban guidelines regarding the effects of the transformations of ground floor interfaces from traditional to contemporary buildings in the perception of security and the occurrence of crimes in public open spaces and in neighbouring residential units. It is further evidenced the need to recognize the ground floor interface as an element of public interest, even if it belongs to a private property. Nonetheless, further research is needed on the relationships between the quantifications of the levels of visual and functional permeability, the different types of uses on the ground floor of buildings, movement of people and crimes in open spaces and buildings in different periods of the day.