The building in the 19th and 20th century

From the mid-19th century onwards the house at Bonngasse 20 went through a very diverse history. After the door had been substantially widened in 1836, an inn called "Beethoven's Geburtshaus" (Beethoven's birthplace) was opened on the ground floor in 1873. The remaining rooms were home to three craft workers' families as well as the innkeeper's family. In 1887 a "beer and concert hall" was added in the courtyard. A colonial merchant took over the house in 1888, but put it up for sale again in 1889.

The city of Bonn was not interested in buying the house, so in 1889 the Beethoven-Haus Society was founded with the aim of purchasing the house and establishing a memorial to the composer. Large parts of the building were still in the same state they had been in since the second half of the 18th century. The ground plans of the front building were altered to ensure that the museum's rooms were generous in size. Space was also made available for the Society's office, library and an apartment for the caretaker. The structural changes to the rear building were mainly limited to the staircase and passageways connecting it to the front building. The inner courtyard was remodelled to include trellises, sandstone paving stones and a garden in place of the "beer hall" which had been demolished. It has remained so ever since. The house was officially opened on May 10, 1893 during the second chamber music festival.

Aside from continual restoration work, the first major renovation was undertaken in the mid-1930s. It also included the neighbouring house "Im Mohren", in which the Beethoven Archive was housed. The relatively small amount of damage it had suffered during the war was put to rights at the beginning of the 1950s. At the end of the 1960s the house underwent major restoration work for a second time and again between 1994 and 1996. Today, the museum is spread over both houses.