In this paper, we investigate the possible impact of crowdsourcing on organisational practices. We answer the research question of whether and to what extent the practices of crowdmapping impact humanitarian organisations. To answer this question, we examine a crowdmapping initiative during a natural disaster. The data collection is based on forty interviews with different actors including crowdmappers, humanitarian organisations, government specialists and technology providers. Concepts from structuration theory are applied to conceptualise and make sense of the data. The findings reveal the process of change that took place in the practices of a humanitarian organisation. They also show that these changes recursively impacted the practices of crowdmapping. We then argue that there is a duality of change between the micro-practices of crowdmapping and the macro-practices of a humanitarian organisation. The implications of the study on research and practice are then discussed.