[6]: 7  In 1798, additions and improvements were made including the roofing of a workshop and storehouse, construction of a watch house, an apartment for the clerk, a joiners shop and a smithy.

By 1804, a long open fronted building, probably a boat shed, had been constructed along the George Street frontage, and is illustrated in various views of Sydney Harbour.

Wallis' drawing of the West Side of Sydney Cove, prepared between January and May 1816 shows the completed two-storey stone building located on the waters edge.

[7]: 17  The coxswain supervised shipping on the harbour and was responsible for rostering the boat crews who were employed in the procurement and transportation of timber, grass, shells (for lime) and stores.

[6]: 14  Though this location is rather vague Kent believes that it does refer to Cadmans but as there is no documentary evidence that any construction was done at this time, or that the funds were spent, questions that the Water Police actually took over the building in this year.

In 1950, Cadmans was described as "consisting of four rooms with the usual conveniences", with a galvanised iron roof, and with its main entrance being from George Street, and steps cut in the rock to the site.

In 1970, the Sydney Cove Redevelopment Authority took control of The Rocks and Cadmans Cottage was proclaimed as a Historic Site, under the National Parks and Wildlife Act, two years later.

[2] In 1972 Philip Cox, Storey and Partners, architects designed and supervised work on the building, removing much of the archaeological and architectural evidence of changes to the Cottage.

[2] In 1988 a major archaeological investigation of the site was sponsored by Comrealty Pty Ltd. A large volunteer work force, under the direction of Service Archaeologists carried out excavations within the lower rooms and in the area beneath the paving on the eastern side of the building.

[2][13]: 2–7 The shoreline in front of Cadmans originally (in 1816) consisted of water-worn sandstone bedrock, which was subsequently overlain by sand deposits following the construction of the Coxswain's barracks.

While claims for Greenway's involvement have not yet been substantiated the building was designed and/or built by an experienced builder or architect as it demonstrates a number of features of "well considered architectural detailing and proportioning".

[2] The details of the roof (the gable ends) and the symmetrically placed (smaller than existing) chimneys are shown in a pencil sketch by Robert Russell, dated June 12, 1836, held in the Dickson Galleries in Lempriere, Thomas James.

An open covered walkway linked Cadmans sketch is very similar in appearance to Hyde Park Barracks and, though of a much small scale, is still clearly an official institutional structure with non of the cottage-like characteristics it later acquired.

The addition, a single-storey, late Georgian sandstone structure, with two tall arched openings in the eastern facade, parapet and hipped roof, was designed sympathetically to complement the original building.

Apart from holding the position of Colonial Architect other evidence taken as suggestive of Lewis' involvement are features in the extension considered reminiscent of buildings designed by him.

A sewerage pipe was installed in a trench cut into the bedrock and five separate sewer lines were attached at metre intervals, probably with the toilets facing south with the central dividing wall to the rear.

[2] Cadmans was proclaimed a Historic Site under the National Parks and Wildlife Act in 1972 and Philip Cox, Storey and Partners were engaged to restore the building.

The door to the 1816 lower room was returned to its (likely) original width, revealing the sandstone lintel engraved with the letters G. R. This indicates the building was erected during the reign of George III, like The Commissariat Store, now demolished.

The plaster or render which covered the lower floor and the western side of the building was removed and the walls were resurfaced with lime wash. Extensive repairs to the external and internal masonry were undertaken and the doors and windows were replaced and painted green.

Some of the features of the site, including the steps to the cottage at the north-eastern end, and the archaeological deposits under the sandstone flagging and in the southern room also date to this significant phase.

Cadmans was a focal point of the harbour upon which the city relied and indicates the extent to which government regulation of the colony depended on control of its waterways.

The first two stages of the building's occupation, the Coxswain's and the Water Police phases, are both periods little researched, but of considerable interest in Australian history and are best represented in the surviving fabric.

[2] While claims for Francis Greenway's authorship are still unsubstantiated, the fine Georgian styling demonstrates that Cadmans was built or designed by a competent and experienced builder or architect.

The shop contains information and objects that are irrelevant to the history of the building or to Sydney Cove, being largely indistinguishable from items on offer through The Rocks and this increases the incongruous feeling.

[2] In summary Cadmans Cottage Historic Site has social significance on a national level because of its age, its survival on the original shore line of Sydney Cove and its association with an early colonial family.

[2] Cadmans Cottage has great potential to tell the story of the growth of Sydney, to illustrate the changes to the face of the harbour and to explain the importance of the Government maritime role during this period.

[2] Cadmans Cottage also has major potential as a vehicle for the Service to tell and sell the story of its historic sites, particularly those around the harbour which to some extent share its history.

The Service is the state government department with the greatest responsibility for managing a range of historic resources, although its public image is primarily of a nature conservation organisation.

[2][14]: 15 The courtyard/reclaimed area in front of the cottage, investigated by Thorp in 1986, lacked evidence pre-dating the construction of Cadmans and the first two phases of occupation by the Government Coxswain and the Water Policy.

The upper floor of the building also has the potential to provide information unavailable from historical sources about the use of these rooms and the impact of the 1972 work on the surviving fabric.