A detailed live load survey was carried out on floors of the library and newspaper archive at a public library in Mexico City. The study included furniture, racks and shelves, as well as books, journals, papers and other items used in libraries. Considering temporal concentration, an additional survey of people was estimated separately. Those loads were used to estimate distribution functions of the maximum total live loads for different areas. The results were compared with the values specified by the Mexico City Building Code and ASCE 7-16. The paper provides some detailed background behind the normative methodology of the current specialized codes to define the basic value of design live load intensity by considering the maximum load effect as a function of the building uses and the definition of influence area by structural element. The results of the survey corresponding to typical public libraries have shown that the probabilities of occurrence of the design loads recommended in the local code might be a proper representation of the mean values. Based on the results, basic values of design load intensity were proposed.