Open-plan living areas are one of the defining features of contemporary suburban architecture in spatially expansive nations like Australia, the United States, and Canada. In these contexts, the European and modernist meanings of 'open plan' are joined by relations between parents and children and identities associated with motherhood and homemaking. Using a feminist and material-culture analysis of the practices of living open plan in this distinctive historical and geographical context, this paper offers a different interpretation of the social significance of the open-planned domestic interior. Drawing on research conducted with residents of new, open-planned houses on the outskirts of Sydney and, in particular, mothers' narratives of the materialities of their home and the place of children and open plan within it, I show how open plan is held together, as a material and imaginative space, by a balancing of aesthetic considerations and the materiality and anxieties produced by children. The processes of living open plan entailed accommodating family ideals and practices to suit the house and/or altering the house to suit the family: banishing children from open-plan areas to maintain their simplicity; embracing children's presence; placing furniture to enclose it; knocking out walls to open it.