Hornby Lighthouse at Watsons Bay - scope design

NSW Public Works, Heritage Environment and Planning team provided historic and technical research, advice, and tender documentation for conservation works to the Hornby Lighthouse.

Historical research and a heritage assessment provided context, level of significance and established that the unusual vertical red and white stripe colour scheme on Hornby Lighthouse was an original feature dating from 1858.

Modern paint systems can often have a devastating effect on the long-term conservation of sandstone, which is the principal building fabric of Hornby Lighthouse. This is primarily due to the lack of breathability of modern paint systems which prevent water vapour passing through sandstone (or masonry), trapping moisture causing salts and mould to build up or even blowing the paint and surfaces of the stone off completely.

Complete removal of the painted finish was ruled out for the following reasons:

• The early paint systems and layers provide important historic evidence and a record of changing paint technologies.
• The paint systems and colour scheme are a unique navigational identifier, enhance the historic character of the lighthouse and aid the interpretation of overall heritage significance.
• Evidence of historic paint finishes are rare within the setting and amongst lighthouses.
• An alternative to non-breathable, modern paint was needed to prevent damage to significant sandstone and prolong its functional life.

The objectives of the replacement paint system sought to achieve the following:

• Conservation of the significance of Hornby Lighthouse
• Provision of paint finishes that accurately reinstate and enable the maintenance of the historic presentation of the building its colour finishes and relationship to the setting.
• Provision of paint systems that serve to conserve the significant fabric of the Hornby Light including evidence of the chronology of paint finishes since initial construction in 1858.
• Provision of paint finishes that establish a sustainable time sequence of maintenance and replacement having due regard to the extreme environmental aspects of the location.
• Provision of Conservation works that serve to maintain and enhance interpretation of the Hornby Light  for its continuing service as maritime aide and as a thematic [scenic] element within Sydney Harbour Foreshores National Park.

Analysis of the comparative performance of readily available paint systems on exterior stonework was undertaken that took into consideration the following properties:

• Adhesion
• Absorption
• Chemical bonding
• Mechanical interlocking
• Breathability
• Colour fastness

Samples, trials and testing of a variety of suitable paint systems was undertaken.