Some 14–17% of adults over 65 are lonely. Social isolation and the subjective experience of loneliness can increase the risk of poor health outcomes, including anxiety, depression, suicide, sleep problems and premature mortality. Cohousing is a form of grouped housing designed and managed by those who reside within it. We consider whether this approach may have beneficial effects in alleviating or protecting from loneliness in older people. This is part one of a two-part article.