His parents were Earl and Helen Severs of Escondito, California, USA. Dennis Severs visited England in 1965 and moved to London in 1967 after his high school graduation. He first planned to become a barrister, but changed his plans, and in the late 1960s he was running horse-drawn open carriage tours around Hyde Park and the West End. However, this business came to an end when his stable near Gloucester Road was demolished by a developer.

In 1979 he bought the brick George I terraced house, built in 1724, at 18 Folgate Street, Spitalfields, on the edge of London's East End. He developed this as a living museum. At the time there was a campaign to restore Hawksmoor's church nearby. The Spitalfields Historic Buildings Trust were fighting to conserve the inner suburb. Gilbert and George had already moved into Fournier Street. Also nearby lived Raphael Samuel whose book Theatres of Memory celebrated the restoration of the past.

Dennis Severs began by sleeping in each of the house's ten rooms to judge their atmospheres. He invented a family of Huguenot silk weavers called Jervis who he pretended had lived in the house for five generations. Paying visitors were entertained by re-created rooms with taped sound effects, but those who did not take it seriously were ejected. His unpublished guide to the house was The Space Between.

Dennis Severs had been diagnosed as HIV-positive for some years before he died at the Mildmay Hospice of cancer of the lymph glands at the age of 51. He was buried in Norfolk.

The house had been bought by the Spitalfields Trust, but there was some doubt about whether it could be conserved in the same way. The Dutchman Mick Pedroli became the house manager after the death of Dennis Severs.