Rue Franklin Apartments by Perret’s are considered to be the first reinforced concrete building in history of Architecture.

image source: http://www.architecturedecollection.fr/architecture/immeuble-rue-franklin/

The building of the Franklin Street is the perfect type of a modern luxury building: elevator, cellar, electricity, bathroom, toilet, telephone, caretaker and rooms for the domestics. The building was moreover considered from the beginning as its comfort and its modernity. It adopts all the possibilities for modern building and the use of new materials. The reinforced concrete skeleton and the cover of ceramic floral decorations assures the elegance and the lightness of the building. With this building Perret wanted to achieve efficiency, quality and a good arrangement of spaces.
image source: http://www.architecturedecollection.fr/architecture/immeuble-rue-franklin/
mAIN INFO
Architect : Auguste Perret Location: Paris, France
Construction period: 1902 to 1904 Style: Early Art Deco
Building : apartment block
The SKELETON

While combining his modern conception of the architecture and the use of a new constructive method as well as the state-of-the-art materials, Auguste Perret succeeds in realizing ta building with a visible skeleton. It consists of posts arranged in the extremities of the segments which divide up the internal space. Walls are not any more carriers as in the traditional constructions.
image source: http://www.greatbuildings.com/buildings/Rue_Franklin_Apartments.html
The plan

This skeleton allows for every floor to have an arrangement of possible partitions of rooms, according to the desires of the inhabitants. Each floor is organized with the main and service stairs to the rear (each with its own elevator), the kitchen to one side and the principal rooms to the front. These last are divided up from left to right into rooms assigned to smoking, dining, living, sleeping and reception.
image source: http://hiddenarchitecture.blogspot.com/2015/06/rue-franklin-apartments.html
info source: https://en.wikipedia.org/wiki/Auguste_Perret