A two-storey Federation Arts and Crafts style residential building () with much of its original details intact. It was built on the site of Thrupp's cottage, one of the earliest buildings on the North Shore and has been leased throughout the years as a high class boarding house. More recently it has been owned by the Commonwealth Government and used by the Department of Defence (Air Force). The house has been converted into units. The interior of Unit 4 is significantly modified. Unit 1 retains decorative features including plaster ceiling roses, cornices, joinery. Tesselated tiles on balcony. Notwithstanding the substantial changes it has experienced, 2 Hayes Street presents as a fine example of the Federation period Arts and Crafts style. The additions and alterations in the 1980s have captured the characteristics of this distinctive style, maintaining the typical asymmetry and variations in the use of architectural forms and devices. To the extent that the new work blends so successfully with the retained original fabric and features the aesthetic and technical values of the building are somewhat false because it is only after a close inspection on site and study of drawings that the various phases of the buildings evolution can be understood. The site still retains architectural evidence of earlier occupation in the form of stone steps associated with Thrupp's Cottage (possibly the oldest residence on the North Shore), remains of a woolstore (), a reservoir and associated conduits () and, to the west, the stone cellar walls of "Craignathan", also built and operated as an early twentieth century boarding house. The building's internal fabric has been substantially altered to convert it to three residential units, leaving no clear physical evidence of tis origins as a boarding house or its use as the headquarters of the support units of the RAFF from 1956 to the mid 1980s. However, the imposing presence of its exterior in this prominent location serves to preserve the record of its origins and use and the history of urban development along the northern shoreline of Sydney Harbour. Hastings was listed on the New South Wales State Heritage Register on 2 April 1999.