For some seventy years Wairoa was the summer residence of three Adelaide gentry families — the Horn, Barr-Smith and Gosse families.
William Austin Horn (1841 – 1922) purchased the Wairoa site in 1888 and by the early 1890s he had completed construction of most of the house. Horn was a notable and somewhat eccentric character in South Australia’s history. He amassed a considerable fortune from mining and pastoral leases and he was a member of the South Australian House of Assembly from 1887 until 1893. Horn was also a philanthropist, a classical scholar, a bushman, a sculptor (his stone sculptures are features of the Wairoa garden) and an author.
The architect and builder of the house are not known, however George Sparrow was engaged by Horn to design and lay out the garden. Sparrow continued working at Wairoa as head gardener until his death in 1913.
In early 1896, Horn decided to live in England and sold the property to Tom Elder Barr-Smith. Tom and his wife Mary Isobella (Molly) and their five children used Wairoa as their summer house for the next thirty years. During this period the Barr-Smiths made a number of alterations to the house, including the building of an adjoining guest house and smoking room, the gatehouse and a new driveway. They also refurbished the interior of the house with William Morris wallpapers, curtains and rugs. In the garden too, Tom and Molly introduced new plantings and made extensions — notably the construction of the picking garden.
The house was passed to their eldest child, Joanna (Gosse) in 1941. Lady Gosse was very fond of Wairoa and spent much time there. Upon her death in 1965, the property was sold to Screenings Pty Ltd.
Between 1972 and 2004, Wairoa served as the campus for a small independent progressive school, Marbury. Over those years hundreds of children and adults enjoyed Wairoa and many continue to have a special attachment to the place.
In 2007, the original thirteen hectare property was community titled. Now the property is owned and occupied by a group of families who continue to care for the old house and garden.