This paper explores the challenges of everyday practices of cooperation in UK shared housing co-operatives, situated within literatures that stress the relational basis of these practices and the centrality of 'critical associations' to the conduct of everyday life. Shared housing co-operatives, based on mutual ownership and co-residence between unrelated adults, represent a radical departure from both the traditional landlord/tenant model of shared housing and newer models of shared provision such as co-living developments. They allow sharers to access affordable housing through effectively become their own landlord. Yet the practices of co-operation that generate these benefits are challenging, necessitating high levels of commitment to a common ethos and involving an unusual mix of both formal and informal ways of relating to co-residents. These features are explored in this paper. The paper concludes that, despite wider societal pressures towards the commodification of housing, the structures and norms of shared housing co-operatives allow them to transcend the strengths and weaknesses of their membership at any given time, and hence facilitate an unusual alternative to more widespread models of sharing in the private-rented sector.Equilibrando lo formal y lo informal: los desafíos relacionales de las prácticas cotidianas de cooperación en cooperativas de vivienda compartida en el Reino Unido RESUMEN Este artículo explora los desafíos de las prácticas cotidianas de cooperación en las cooperativas de vivienda compartida del Reino Unido, situadas dentro de la literatura que enfatiza la base relacional de estas prácticas y la centralidad de las 'asociaciones críticas' en la conducción de la vida cotidiana. Las cooperativas de vivienda compartida, basadas en la propiedad mutua y la co-residencia entre adultos no relacionados, representan una desviación radical tanto del modelo tradicional de propietario/inquilino de vivienda