Transport House is a 20th century Grade B+ listed (HB26/50/234) building, designed by J.J. Brennan in the International Style, constructed between 1956-1959 as offices for the Amalgamated Transport & General Workers Union. The building's design was inspired by the contemporary design of Busáras, the bus offices and terminus in Dublin, which was opened in 1953. The seven-story building is cladded in pale green tiles, with concrete cladding and brown bricks also visible in some areas. One of the narrow sides of the building is concave and decorated with a Soviet Constructivist-style tiled mural depicting images of industries such as ship-building cranes, a plane, and a factory, as well as male workers.

Transport House was originally listed as B1 in 1994 but was resurveyed in 2012 and awarded a B+ listing (HB26/50/234).

Transport House is a two-block building, with one block being seven storeys high and the other being five storeys. The building has office accommodation split over four floors, each with a footprint of 385m2 per floor. Additionally, several minor plant rooms are located on the upper levels. Transport House is served by two staircases situated at either end of the building and two lifts located near the entrance, but they are currently not in operation.

In June 2007, the Amalgamated Transport & General Workers Union submitted a planning application (Z/2007/1430/F) proposing a first floor extension to the side and back of the existing building to house new offices and meeting rooms. The proposal was granted planning permission in April 2008.

In 2007, the sign at the top of the building, formerly reading ‘T.G.W.U. (Transport and General Workers’ Unions) was replaced when Unite the Union, Britain’s largest trade union, took over the premises

By 2012, the building was vacated by Unite and has remained unoccupied since, with no live services currently in the building.

In September 2021, Unite General Secretary Sharon Graham announced plans proposing to refurbish and re-open Transport House on High Street.

In December 2022, Unite the Union submitted a planning application (LA04/2022/2266/F) proposing alterations to an existing office building and a roof top extension to house a multiuse meeting space and break-out room. This application was approved in May 2024.

In January 2024, work commenced at Transport House preparing the site for refurbishment with hoarding being erected around the building. The hoarding set up was completed in March 2023.