Longbeach Station was established by John Grigg (1828?-1901) who arrived in New Zealand in 1854. He began farming at Otahuhu, near Auckland but, in 1863, purchased 2,135 acres (864 hectares) south of Ashburton, in partnership with his brother-in-law Thomas Russell. Russell withdrew from the partnership in the early 1880s, resulting in the loss of almost half the land and one-third of the stock. Despite this Grigg, and later his eldest son, managed to turn the property into one of the largest and most impressive farms in the country. As the estate developed, Grigg employed between 160 and 200 people on a permanent basis and a small village was established on the Longbeach estate to house all the workers. Grigg provided a post office, school, store and church for his employees, and his kiln produced bricks that were used in the construction of the various Longbeach buildings.

In 1926 Longbeach passed to John Hutton Grigg who owned the property until 1973. The current Longbeach Homestead, the subject of this registration, was designed for him by the architectural firm of Helmore and Cotterill in 1937. It was built to replace an earlier homestead that had been destroyed by fire, and one of the requirements for the new homestead was that it would harmonise with the already established gardens.

Helmore and Cotterill provided three designs for Grigg. The first was symmetrical with a double hipped roof and pilasters. The second was more in the style of earlier colonial homesteads with gables and dormer windows. This second design apparently proved too expensive and the architects produced a third, completely different, proposal. In contrast to the earlier proposals their third design was asymmetrical. The gables of the final proposal are more steeply pitched with some being irregular in length and irregularly positioned. The re-use of the burnt bricks from the earlier homestead, in conjunction with red bricks from Ashburton, the timber of the window frames, and the dark brown of the roof shingles, along with the asymmetric plan, give the impression that the house grew organically out of the surrounding gardens. This impression of Longbeach, as an intrinsic part of the landscape, is said to be similar to that of Edwin Lutyens' 'Munstead Wood' (1893-1897), a house built for Gertrude Jekyll in Surrey, Britain. Helmore had been taught by Lutyens and it would seem likely that he was influenced here by Lutyens' early Arts and Crafts work. Of all the buildings Helmore and Cotterill designed, Longbeach is the only one with such a clear connection to the British Arts and Crafts style. However, Longbeach is not a direct copy of Lutyens' work. Robert Esau has argued, in his thesis on Helmore and Cotterill, that Longbeach 'in many respects...reflect[s] the growing influence of the Modern Movement' with its clean crisp lines, sharply defined angles and simple shapes.

The Longbeach homestead, in conjunction with the chapel, cookshop, stables, sod cottage, flourmill and waterwheel (all registered as historic places), is significant as part of the Longbeach estate, historically one of the largest and most impressive farms in New Zealand. The house itself is important as an unusual example of Helmore and Cotterill's domestic work, and has been praised as their most outstanding achievement.