This study examines public shelters that were built by non-government organizations for people displaced by the Great East Japan Disaster (2011).As alternative common spaces that complement the common rooms established in temporary housing sites,public shelters provide the following functions :1) Facilitating communication: In addition to displaced people in temporary housing sites,neighbors,volunteers,officers of NGO,and government officers can visit public shelters.2) Escape from temporary housing site communities: Communities in temporary sites can be closed and tightly bonded.Residents who hesitate to join such communities can use public shelters.3) Hosting various activities: Certain activities that are forbidden or avoided in formal common rooms are possible in public shelters.These fewer restrictions generate more varied and active usage.These functions are realized through the characteristics of public shelters,as follows:1) Independence from temporary housing sites: The public shelters are not located in the temporary housing site but adjacent the site.This situation enables existing residents around the temporary housing site to visit public shelters easily.2) Self-built construction through collaboration: Public shelters are built by hand through the collaboration of displaced people and volunteers and with the support of architects and NGO.This participatory process establishes the basis for the active and free usage of public shelters.3) Typical architectural vocabulary: The use of a typical architectural vocabulary in the public shelter lends a sense of easy access,easy communication,and healing.