This Sunday marks a milestone for Melbourne’s Metro network: new stations open their doors for the first time, expanding access and connectivity across our beloved city. It’s a fitting moment to reflect on the unsung hero behind decades of infrastructure and construction: plywood.
In the construction of underground metro systems, plywood has often played a supporting but critical role. From early “cut-and-cover” style subways to more modern tunnel-boring projects, plywood has been used for temporary formwork, shuttering, and structural support during excavation and concreting. This blog post explores how plywood has been deployed historically and in contemporary practice, analyses the advantages and challenges, and reflects on whether plywood remains appropriate - or even safe - for modern metro projects.
Photo: J.J.C. Bradfield, State Library of New South Wales (PXD 305)
Hyde Park in Sydney was dug open to build the city’s first underground stations, Museum and St James.
A Brief Historical Context of Underground Railways
The first urban underground railway, London’s Metropolitan Railway, opened on 10 January 1863. It was constructed largely by the “cut-and-cover” method. After digging a trench along streets, builders would install the tunnel and station structure, then cover it over and restore the roadway.
In those early days, timber, including wooden beams and shuttering, was widely used for temporary supports while masonry or brick vaulting was erected. The streets above could be reopened to traffic and pedestrians even while construction continued below. The use of temporary woodwork made this feasible and relatively cost-efficient.
As subway technology evolved, engineers moved away from brick-and-timber “vaulted arches” toward deeper, bored tunnels with cast-iron or concrete linings, reducing reliance on wood.
How Formwork Plywood Has Been Used
In metro or tunnel construction, formwork plywood often supports cast-in-place concrete slabs for station boxes, passages, or other structural elements. Formwork plywood is chosen for its strength, its capacity to bend or be shaped (if required), its relative lightness compared to steel, and its reusability.
In some tunnel construction projects worldwide, plywood or timber formwork was used to build temporary separation slabs, ventilation passages, or internal support levels within the tunnel during excavation.
More recently, as shown in large projects like Melbourne’s Metro Tunnel, temporary structures such as acoustic sheds (used during construction to reduce noise, dust, and light impacts) are built, used, then dismantled and recycled. In such cases plywood or similar panel products may be part of the temporary installation.
By Gracchus250
Advantages of Using Plywood in Metro Construction
Plywood offers several practical benefits:
Plywood is relatively inexpensive compared to steel formwork or custom moulds. Its cost-effectiveness is particularly valuable for temporary structures in large infrastructure projects where huge volumes of concrete must be formed.
It is flexible and can be cut or shaped on-site, allowing adaptation to non-standard geometries that are common in tunnels or station boxes, such as curved walls, vaults, or irregular cross-sections.
It is lightweight compared to many alternatives, making handling, erection and dismantling easier, especially in constrained underground sites where transport of heavy materials is challenging.
In many cases, plywood formwork can be reused multiple times (assuming proper handling, maintenance, and storage), improving overall resource efficiency.
However, many jurisdictions now have stringent fire safety regulations for tunnels and underground stations. Non-combustible materials are generally required for permanent structures. This means plywood is largely relegated to temporary roles; its use in permanent finishes or as ongoing support would often be unacceptable.
Is Plywood Still Appropriate for Modern Metro Projects?
Given the risks and constraints, plywood’s role in contemporary metro construction is limited and carefully controlled. Its value lies primarily in temporary functions: formwork during concrete pours, protective shuttering, temporary acoustic or dust-containment sheds, and short-term support structures during excavation.
That said, plywood remains a useful tool in the engineer’s toolkit, particularly in early construction phases where speed, and cost-efficiency are essential. Its careful and responsible use, aligned with safety procedures, high-quality materials, moisture control, and fire safety management, can still contribute meaningfully to efficient metro station construction.
Plywood has played an important supporting role in the historical and ongoing construction of underground railway stations. As cities continue to expand their underground infrastructure - like Melbourne’s Metro Tunnel does - the priority must be safety, longevity, and compliance with fire and structural regulations. Plywood can be a workhorse tool on site, but it should not be part of the finished underground environment meant to serve the public for decades.
