[1][6] In this role he supervised the building of Governor Lachlan Macquarie and his wife's additions to Old Government House, Parramatta, in the mid 1810s.

It is possible that these works influenced Rouse to build a bigger house than he first intended, adding larger, longer rooms behind the front range.

[1] A number of the property's outbuildings finished construction following the completion of the house, including the laundry wing, cottage, barn and woolshed.

[5][1] A summerhouse, woolshed and a two-storey service wing was added in the 1860s, the stables built in 1876 and 1877 and the house redecorated and partly furnished in 1885.

A verandah, weighted sash windows, a modified front door and sidelights and other late 19th century innovations were also installed.

[11][1] The Heritage Council's Restoration Steering (HC RS) Committee resolved to have a conservation statement prepared for the buildings and their site.

The HC RS Committee considered the need for accurate documentation of interior finishes and contents of the buildings and for curatorial and materials conservation work to be carried out.

[1] Since 1978 descendants have returned many significant family items and the collection now comprises over 20,000 objects as diverse as costume, furniture, tools and automobiles.

In 2007, anticipating the extraordinary residential growth in the area, the HHT sought funding of $19m from Treasury to provide new visitor and cultural facilities (interpretation, programs, research and access to the collection) along with commercial activities (cafe, retail, auditorium and flexible public spaces to be used as venues).

[10] Advocacy by the Friends of the Historic Houses Trust was in large part responsible for moving the road to create this bypass, protecting the site's setting from encroachment.

[1] In 2009-10, the construction program was almost complete on former RTA land and Rouse Hill Public School (former) adjoining re-aligned Windsor Road.

HHT historians Joy Hughes, Jane Kelson and curator Fergus Clunie began gathering historic maps of the region.

Although the road has long since disappeared, it defined the boundary of the first land grant in the area, the 1000 acre "Copenhagen" given to Captain William Bligh.

It also ran close to the surviving kilometre stretch of the old Windsor Road built by convicts in 1812-13 as the first turnpike in the colony between Sydney and the Hawkesbury.

As the likely site of the battle of Vinegar Hill, it now has a new level of significance, with exciting interpretive possibilities, and this has encouraged HHT to rethink its approach to the property.

[15][1] Since its establishment in 1813, when the house was begun on the 180-hectare (450-acre) property, the following modifications have occurred:[1][12][14][16][17][13] Rouse Hill Estate is arguably unrivalled in Australia for the wealth of physical evidence of its own history and its use by the family which built it.

The main house is built of sandstone with a slate roof, timber floors (kitchen, scullery, staircase, hall, arcade and verandah are flagged) and oakgrained hardwood joinery.

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.

[1][20] Picturesque building in the garden thought to have been built by Scottish-born Parramatta builder and architect, James Houison, it originally featured ine arched timber trellises on the two verandahs and porches on each side.

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.

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.

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.

[19][1] Rouse Hill Estate was listed on the New South Wales State Heritage Register on 2 April 1999 having satisfied the following criteria.

[24][1] The place is important in demonstrating aesthetic characteristics and/or a high degree of creative or technical achievement in New South Wales.

[1] The aesthetic responses to the place depend on the diversity of the visual evidence - in the building, range of decorative and applied arts, garden and the agricultural surrounds, and their interconnectedness.

The family history is representative of a class of people who survived the 1840s depression to rise to social prominence in the second half of the 19th century.

It encompasses:[18][1] The place has potential to yield information that will contribute to an understanding of the cultural or natural history of New South Wales.

The property is significant for: The place possesses uncommon, rare or endangered aspects of the cultural or natural history of New South Wales.