This article investigates participatory action research workshops from the perspective of feminist new materialism by asking, how we came to know ageing in the smart city of Oulu in northern Finland through collaborative workshops which aimed to include seniors into public service design. The most meaningful socio-material components in this knowledge-making are argued to be the shifts in social power relations, particular spatial and material practices, and the participant assemblage. These components intra-act transferring our understanding on ageing: ageing becomes a creative state where the seniors are included in the problem-solving instead of being citizens to be looked after, and thus being merely a socio-economic problem. The power dynamics are essential in participatory action research, therefore, the accountability of all agents should be carefully analysed to understand the impacts of epistemology both in design and social change.