The national lockdown in response to the COVID-19 pandemic has revealed the prevalence and importance of informal mutual support in neighbourhoods and social networks. Mutual support structures and functions are strong in collaborative housing, in which people often intentionally form resident communities to enhance support practices. Using qualitative methods, this article examines how lockdown restrictions have impacted on practices of mutual support in collaborative housing, when the infrastructures of shared facilities and proximate neighbourliness were challenged. There were ambiguous definitions of ‘households’ associated with collaborative housing communities when interpreting the lockdown rules to provide mutual aid and support. Shared values, commitments and length of time of establishment mattered when operationalising such support. Moreover, the lockdown helped some communities re-evaluate their governance structures, decision-making and the limits of mutual support as they experienced what changing care needs of individual members meant to their communities. It resulted in a more realistic appraisal of their local social capital.