Trades Hall was built incrementally in approximately ten phases, primarily between 1874 and 1925, during which its notable classical facade along Lygon and Victoria Streets took shape. Predominantly a two-storey structure resting on bluestone foundations, it features an imposing facade marked by Corinthian elements, including two distinct towers flanking a central triangular pediment at the Lygon Street entrance. Large decorative urns atop the parapet characterize the Victoria Street section.
The architectural firm Reed and Barnes, alongside its successors, oversaw the early phases of construction, which extended from 1873 to 1926. However, later additions, notably the 1960s office block at the rear, contrast unfavorably with the original architectural vision.
Trades Hall holds considerable historical, social, and architectural importance in Victoria. Historically, it symbolizes Victoria’s pioneering role in the eight-hour day movement, reflecting its significance as a landmark for labour achievements. Constructed on the site of the initial 1859 temporary Trades Hall, it has continuously served as a central gathering place for pivotal events and movements shaping trade union and working-class history, including the origins and early developments of both Victorian trade unions and the Australian Council of Trade Unions. The building notably commemorates leaders and achievements of the labour movement through honour boards, flags, and banners preserved within its interior.
Politically, Trades Hall played an important role in the birth and growth of the Australian Labor Party, housing its headquarters until 1972, and supported significant political groups, including Berry's Liberal protectionist faction in the turbulent politics of the 1870s. Trades Hall remains today an active focal point for union activities and progressive politics.
Socially, the building acts as a living centre of radical political and union traditions. Its collection of banners, flags, and honour boards offers tangible insights into over a century of Australian labour history.
Architecturally, Trades Hall is celebrated as an exceptional example of 19th-century institutional architecture designed by the eminent firm Reed and Barnes. Its conservative style expresses the respectability sought by its founders, while construction records highlight the pride Victorian building unions took in its construction. The building is recognized as a rare intact example from this period, featuring superior craftsmanship, local materials, and skillful execution. Architect Joseph Reed significantly influenced Melbourne's architectural heritage, contributing to iconic buildings such as the Melbourne Public Library, Rippon Lea, Melbourne Town Hall, and numerous other significant structures throughout the city's period of rapid growth in the late 19th century.
The complex, situated on land originally secured by Victorian trade unions, was progressively developed between 1873 and 1926, evolving from a modest initial structure to an extensive complex. This staged construction culminated with final additions in the early 1920s, resulting in a coherent architectural ensemble recognized today as a prominent Melbourne landmark and testament to the region's vibrant union history.