Voussoirs: An engineering legacy
- computers67
- Jun 3
- 3 min read
A voussoir is a wedge-shaped stone or brick used in the construction of arches. When arranged in a curved formation, voussoirs work together to distribute weight outward and downward, allowing the arch to bear significant loads. The system is stabilised by the keystone at the apex and the springers at the base, which lock the arch into place.
The concept of the voussoir dates back to ancient Mesopotamia, but it was the Romans who perfected the technique. Their development of the true arch, using finely dressed stone and a precisely fitted keystone, enabled the construction of enduring structures such as amphitheaters, bridges, and aqueducts; many of which survive today.
By the medieval period (12th – 16th centuries), the voussoir had become both a structural and visual device. In Gothic architecture, particularly in cathedrals, pointed arches composed of carefully worked voussoirs allowed for taller, lighter buildings and expansive stained-glass windows. This period marked the voussoir's transition from a purely functional element to one with architectural and symbolic significance.
It is notable that the invention of the arch was crucial in the evolution of western architecture. However, in the east in places like India, which has an equally rich architectural tradition, the arch was a relatively late development. Traditional Indian architecture relied primarily on trabeated construction, using post-and-lintel systems and corbelled arches to span openings. The use of voussoirs in true arch construction became more common only after the 12th century, introduced through Islamic influence during the Delhi Sultanate. This shift marked a gradual blending of indigenous and imported construction techniques, particularly visible in later Indo-Islamic and Mughal architecture. The gates of Jaipur’s Walled City, although constructed later in the 18th century, showcase these traditional methods employing both trabeated construction as well as corbelled arches.
Traditional voussoir construction required each stone to be cut into a precise wedge shape, a time-consuming process requiring skilled labour. In response to rapid urbanisation and growing demand for efficient building methods, bricklayers in late 18th century Britain adapted the technique using standard rectangular bricks. By increasing the thickness of the vertical mortar joints and laying bricks along a curved line, they could replicate the function of true voussoirs without the need for custom shaping. This method, often used for flat or segmental arches, became widespread in the 19th century due to its speed and cost-efficiency.
When British settlers arrived in Australia, they brought with them these masonry traditions. The voussoir arch became a key feature of colonial infrastructure, particularly in the construction of railways. Following British engineering standards, Australian railway projects often employed robust masonry techniques, resulting in many bridges and viaducts built with stone voussoirs. A notable example is the Malmsbury Viaduct, completed in 1859 on the Bendigo line. It spans the Coliban River with five large arches, each defined by dressed bluestone voussoirs radiating to prominent keystones. The most famous example of Victorian railway infrastructure, Flinders Street Station, completed in 1909, also features voussoirs expressed in stylised form around the arched windows and entrances along Swanston and Elizabeth Streets.
In addition to structures designed by the Victorian Railways Department, voussoirs are evident in many RBA projects, including the elaborate masonry arches at Mount Ophir Winery and the flat brick arches of the Wodonga Powder Magazine and the stables at Kinross House (pictured below).
Although the advent of steel and reinforced concrete in the 20th century reduced the reliance on traditional load-bearing masonry, the voussoir did not disappear. Today, precast concrete voussoirs are used in modular bridge and tunnel systems. Architects also continue to reference voussoirs for their symbolic and aesthetic qualities, using them to evoke structural clarity, rhythm, and a sense of historical continuity.
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