==== Front Innov Aging Innov Aging innovateage Innovation in Aging 2399-5300 Oxford University Press US 10.1093/geroni/igaa057.2991 igaa057.2991 Abstracts Session 7550 (Symposium) AcademicSubjects/SOC02600 The Housing Experiment: Citizen Science Engaging Older Adults and School Pupils to Assess Housing Accessibility Iwarsson Susanne 1 Brounéus Fredrik 2 mårtensson Knut 3 Granbom Marianne 4 1 Lund University, Lund, Skane Lan, Sweden 2 Vetenskap & Allmänhet, Stockholm, Stockholms Lan, Sweden 3 miThings, Lund, Skane Lan, Sweden 4 Lund University, Lund, Sweden 2020 16 12 2020 16 12 2020 4 Suppl 1 Program Abstracts from The GSA 2020 Annual Scientific Meeting “Turning 75: Why Age Matters”820 821 © The Author(s) 2020. Published by Oxford University Press on behalf of The Gerontological Society of America.2020This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.Abstract Citizen science is gaining momentum as an approach in many scientific fields. However, it is scarcely used in aging research. Since 2009 in Sweden, Public & Science (NGO) has coordinated an annual mass-experiment where thousands of school pupils have collected data that would have been impossible for researchers to collect on their own. Designed as a cross-generational endeavour, the 2020 mass-experiment, the Housing Experiment, is based on scientific methodology for data collection on housing accessibility. The aim of this presentation is to describe the iterative development process involving older adults, stakeholders in the housing sector, teachers and pupils. We will present the app and instructions developed and piloted for data collection, as well as usability and interrater reliability results. With media attention already in the planning phases, this citizen science initiative has the potential to both generate a unique dataset and increase engagement in housing matters concerning the aging population.