The 1960s was a period of rapid change in the construction labour process, whose increased mechanization and complexity represented a challenge to traditional wage systems and forms of organization. Such changes were nowhere more evident than on the Barbican redevelopment site in London, whose construction exposed the contradictions in industrial relations and clarified demands for improved conditions for building workers which resonated throughout London and the country. The paper addresses the complex reasons for and the significance of the bitter disputes on the Barbican from 1965 to 1967. It is set in the context of a construction industry in the process of rapid change through the use of new technologies and the emergence of new or non-traditional occupations, the widespread use of labour-only subcontracting (the ‘lump’) and often chaotic incentive schemes, tensions between design and construction, the risky award of tenders to the lowest bidder, the crude approach of many large construction firms to industrial relations (that included shutting down sites and blacklisting workers), and relatively weak and fragmented trade unions. The Barbican disputes saw the emergence of the London Joint Sites Committee, which went on to play a central role in the Building Worker Charter, to challenge major problems affecting building workers, and to be involved in the 1972 national building workers’ strike. The significance of the disputes lies in the impetus for change that resulted and in the way that building workers set this in train.