Windsor Bridge, Windsor

The original 1874 bridge at Windsor was a timber beam bridge of ten spans, supported on concrete cross girders resting on ten pairs of cast iron cylinder piers with cross bracing, and one pair of wooden piers. The pier sections were cast at Mort's Dock, Balmain, using iron probably sourced from Fitzroy Mine, Australia's first iron ore mine. The bridge was designed by eminent engineer William Christopher Bennett and constructed by William King Dixon and Andrew Turnbull; construction commenced in 1872 and was completed in 1874.

The piers were sunk into the rock below the riverbed as caissons using compressed air; it was one of the earliest examples of the use of pneumatic caisson technology in bridge building.

An additional span of 20 ft was added in 1896 when the bridge was raised by 8 ft, and in 1922 the timber deck was replaced with precast, reinforced concrete beams and a concrete deck and kerbing, designed by eminent engineer Percy Allan. This work was undertaken some 30 years prior to the use of precast concrete beams to bridge building in Australia.

In 2004, NSW Roads and Maritime Services recognised the historical, technical, aesthetic and social significance of the bridge by placing it on its s170 register as a State significant item (no. 4300589).

The NSW Government Windsor Bridge Replacement Project saw demolition of the bridge in 2020, and its replacement with a prestressed concrete, five-span bridge, which opened on 18 May 2020.

Transport for NSW has retained one span adjacent the right bank, and the abutment on the left bank, both of which carry interpretive signage.

Remnants of the demolished bridge which demonstrate significant features of its design and modification, are stored at Hawkesbury Council’s depot.

The bridge was significant for its historical, technical and social values, its research potential, its association with important bridge engineers, and its status as a rare demonstration of pneumatic caisson technology.

Surviving span at the Windsor end, with the new bridge downstream adjacent.. Michael Clarke.

Pre-cast concrete girder from the 1922 upgrading at the Windsor end. This is believed to be the first use of pre-cast concrete in Australia Michael Clarke.

Reinforced concrete beam cast on the bank adjacent to the bridge ready to be moved to bridge. NSW Museums of History. NRS 4481-4-88-[AF00184629].

Pre-cast girder being moved into position on bridge. NSW Museums of History. NRS 4481-4-88-[AF00184630].

Scavenged section of bridge deck stored in Council depot yard, showing pre-cast beams and cast in situ deck. 2024. Michael Clarke.

Bricks recovered from fill of cast iron bridge piers stored in Council depot yard. Note the purpose made curved stretchers and headers, 2024. Michael Clarke.

The anchorage system for the bridge caissons as recovered. The large threaded rod, here cut at bearing level , would have extended deep into hard bedrock, where it would have been locked by a Lewis and then pre-loaded with the large nut. The cross arrangement locks the bolt to the cast iron cylinder of the caisson. 2024. Michael Clarke.

Demolished caissons showing brick lining and concrete fill. 2024 Michael Clarke.

Loading map...

Location map, Windsor Bridge.

References:
Clarke, Michael, Proposal to Nominate as Item of Engineering Heritage Interest, April 2025.