On 23 March 2020 the UK went into lockdown in an unprecedented step to attempt to limit the spread of coronavirus. Since then, many families have found themselves spending an unprecedented amount of time together, with some facing the additional challenge of adapting to changes in who they are living with as some families have found themselves unexpectedly brought back together. School and university closures, the move to remote working, furlough or the loss of employment have all meant that many adult children who had previously left the parental home have returned. Other individuals have moved to provide care and support for a family member or friend who has been ‘shielding’, and conversely some vulnerable and/or older people have moved in with a younger relative or friend. This paper provides an overview of the changes in living arrangements during the Covid-19 pandemic, drawing upon recently available data from five large scale nationally representative surveys, including the second wave of Understanding Society Covid-19 Study, conducted in May 2020 and the special Covid-19 surveys conducted with the participants of the 1958, 1970, 2000-01 British birth cohorts and Next Steps (born in 1989-90). The paper then goes on to explore the impact of the unexpected changes in living arrangements and mental health, as measured by self-reported stress and interpersonal conflict.Data from the Understanding Society May Covid-19 survey shows that for most of the respondents (95.5%) their living arrangements during the three months since 1st March 2020 had not changed. Just over 2% had changed their address and a further 1.5% reported other people had moved in, whilst under 1% reporting people moving out. However, the likelihood of having changed living arrangements varied significantly by age with one in seven of those aged 20-24 reporting a change in living arrangements. Young people aged 16-29 accounted for over half (57%) of all respondents reporting that they had moved themselves. By contrast, respondents in mid-life (45-59) and early later life (60-74) accounted for the majority of respondents reporting other people had moved in or out. Analysis of the cohort data confirmed this picture with nearly a quarter (24%) of the Millennium Cohort Study, currently aged 19 reporting a change in the people they were living with as a result of covid-19, compared to under one in ten of the 1958 cohort, now aged 62. Logistic regression models were used to assess the odds of reporting increased stress and conflict increase amongst those respondents who had experienced a change in living arrangement change compared to those who had not. The results provide strong evidence that those individuals whose living arrangements have changed as a result of the covoid-19 pandemic have a higher likelihood of reported increased stress and family conflict than those whose living arrangements remained unchanged. This has important implications for public health and wider policy as prolonged periods of stress can lead to serious health problems and policy makers need to be mindful that services may need to flex to take these new, albeit for many temporary, forms of living into account.