The building complex has been continuously extended over the years, with eventually eleven houses connected to each other, resulting in a rather confusing interior. At the beginning of the 19th century, Frankfurt historian Anton Kirschner remarked that the Frankfurt city hall had "stairs, yards, halls and rooms in a labyrinthian mixture".
In 1435, the city bought the Frauenrode house, in 1510 the Viole house and in 1542 the Schwarzenfels house, which were all architecturally connected to the main complex.
Then, in 1596 the city council bought the Wanebach house, which stood next to the Goldener Schwan, as well as the building to the left of the Haus Römer, the Haus Löwenstein, and had both of them connected to the Römer. These construction projects were very complicated, since the floor heights of Löwenstein and Römer were radically different.
In 1843, the Frauenstein house and the Salzhaus were added. Finally, in 1878 the city bought the Alt-Limpurg house to the right of the Haus Römer for 214,000 marks. The current neogothic front with a balcony was built from 1896 to 1900. It was initially planned to be much more imposing, but mayor Franz Adickes decided against Kaiser Wilhelm's suggestion and had the front designed in a more welcoming manner.