The Rouse dairy contains a linear row of bails, with a gabled, fibre-cement-clad "milk house" at the western end that held the pumping machinery and generator. As per 1947 plan specifications, the floor was laid with easily washed concrete to maintain strict hygiene. A much earlier timber structure, containing two cow bails for hand-milking, also survives at Rouse Hill House and features in tours of its outbuildings. Other buildings on the site include a slab built cow shed, brick bath house, a reconstructed timber summer house, brick stables. The property also has an extant caretaker's house. Rouse Hill Estate is one of the most significant and substantial houses of the Macquarie period which dates from 1810 to 1822. Rouse Hill Estate is the largest and most complete publicly owned physical record - in the form of buildings, furnishings, artefacts and landscape relationship - of the occupancy and culture of a European-Australian family, encompassing the tastes, fortunes, and endeavours of seven generations from the early 19th century to the late 20th century. The property is perhaps unique for its survival as a largely intact estate with an unbroken chain of occupancy, allowing the survival of major garden and interior elements of every period of its history to the present. This layering of artefacts and fashions is especially prevalent in the gardens where designs and physical details such as edging, fencing, planting containers, bed designs and paths provide a case history for the study of the development of garden practices in Australia. The garden is perhaps Australia's oldest surviving colonial garden in relatively intact form. The surviving physical evidence in the gardens includes borders in a variety of materials, fence and gate remnants, fragments of trellis and arbours, paving and numerous soil displacements that become evident with the location's annual dry spells. These physical remains, matched with pictorial evidence from photographs, drawings and engravings of the property, and writings, have resulted in the identification of four stages of the garden's development: c.1825, c.1865, c.1885 and c.1968. This continuity and evidence of evolution of a very early intact garden from the first quarter of the 19th century to the Edwardian era and 20th century is extremely rare in Australia. Rouse Hill Estate was listed on the New South Wales State Heritage Register on 2 April 1999 having satisfied the following criteria. The place is important in demonstrating the course, or pattern, of cultural or natural history in New South Wales.