Rivets vs Bolts: How the Eiffel Tower Was Fastened
- LTM Engineering
- 2 days ago
- 5 min read
The 2.5 Million Rivets That Hold the Eiffel Tower Together
When people admire the Eiffel Tower, they usually focus on its height, elegance, and iconic silhouette rising above Paris. But hidden within its intricate lattice structure lies one of the most fascinating engineering details of the entire project:
More than 2.5 million rivets hold the tower together.
These rivets form the backbone of the tower’s connections, binding together 18,038 individual iron components into one cohesive structure. Long before modern welding and high-strength bolting systems existed, riveting was the primary method used to assemble large steel and iron structures.
Understanding how the Eiffel Tower was fastened together offers valuable insight into the evolution of structural fabrication, connection design, and steel construction techniques.
The Role of Connections in Structural Engineering
In any steel structure, the connections between components are just as important as the beams and columns themselves.
The Eiffel Tower’s structure consists of thousands of carefully designed members forming a massive lattice framework. Each element must transfer loads safely through the structure and down to the foundations.
Connections must therefore be able to resist:
Compression forces
Tension forces
Shear forces
Wind loads
In the late 19th century, the most reliable method for creating strong connections between iron components was hot riveting.
What Is a Rivet?
A rivet is a permanent mechanical fastener consisting of a cylindrical shaft with a head on one end. The rivet is inserted through aligned holes in the structural members and then deformed to create a second head on the opposite side.
Once installed, the rivet clamps the connected pieces together tightly.
Unlike bolts, rivets cannot be removed without destroying them, which makes them ideal for permanent structural assemblies.
For the Eiffel Tower, rivets were used to connect nearly every structural component, forming a rigid and durable framework.
The Hot Riveting Process
The riveting process used during the construction of the Eiffel Tower was both highly skilled and physically demanding.
The rivets were heated until they became red-hot, making the metal soft and easy to deform. Once heated, the rivet was quickly inserted into the holes connecting the iron plates or beams.
Workers then hammered the exposed end of the rivet to form a second head, locking the pieces together.
The process had to be completed before the rivet cooled, requiring speed and coordination from the construction team.
The basic steps were:
Heating the rivet in a portable forge
Throwing or passing the hot rivet to the installation team
Inserting it through aligned holes in the steel members
Hammering the tail to form the second head
Allowing the rivet to cool and contract
As the rivet cooled, it shrunk slightly, pulling the connected members tightly together and creating an extremely secure joint.
The Famous Teams of Four Riveters
Each rivet installed in the Eiffel Tower required a coordinated team of four workers, each responsible for a specific task.
These teams worked with incredible efficiency, installing thousands of rivets throughout the construction process.
The four-person team typically consisted of:
1. The Rivet Heater
This worker heated the rivets in a small forge until they were glowing red-hot. Timing was crucial because the rivet needed to remain hot enough for installation.
2. The Thrower (or Passer)
Once the rivet reached the correct temperature, the thrower passed it—sometimes literally throwing it through the air—to the installer.
This method might sound risky, but experienced teams became remarkably accurate.
3. The Holder-Up
The holder-up positioned the rivet in the hole and held a heavy metal bar against the rivet head to keep it in place during hammering.
4. The Riveter
The riveter used a hammer or pneumatic tool to deform the tail of the rivet and form the second head.
Together, these four workers formed a highly synchronized system that allowed rivets to be installed quickly and effectively.
Factory vs On-Site Riveting
Interestingly, not all rivets used in the Eiffel Tower were installed on the construction site.
Approximately two-thirds of the rivets were installed in the fabrication workshops before the structural components were transported to the site.
Only the final connections between major components were completed during erection.
This approach allowed Gustave Eiffel’s team to ensure high precision and quality control before the pieces arrived on site.
It also reduced the amount of complex work required at height during construction.
Why Rivets Were Ideal for the Eiffel Tower
Riveted connections were widely used in bridges, ships, and towers throughout the 19th and early 20th centuries because they offered several advantages.
Strong and Reliable Connections
When installed correctly, rivets created extremely strong joints capable of transferring significant structural loads.
Permanent Fastening
Unlike bolts, rivets could not loosen over time because the metal head was permanently formed during installation.
Tight Clamping Force
As the rivet cooled and contracted, it pulled the connected members tightly together, improving structural performance.
Resistance to Vibration
Riveted connections performed well in structures exposed to dynamic forces such as wind or vibration.
These qualities made riveting ideal for large structures like the Eiffel Tower.
The Decline of Riveting in Modern Construction
Although riveting was once the dominant method of steel connection, modern construction has largely replaced it with high-strength bolting and welding.
This shift began in the mid-20th century as new technologies emerged.
The reasons for the transition include:
Faster installation methods
Lower labour requirements
Improved manufacturing precision
Easier inspection and maintenance
Today, riveting is rarely used in new construction projects.
However, it remains an important part of historic steel structures, including bridges and towers built before the widespread adoption of modern connection systems.
Modern Bolted Steel Connections
In modern steel construction, most structural connections use high-strength bolts.
These bolts are specially designed to clamp structural members together with significant force.
Common types include:
Friction grip bolts
High-strength structural bolts
Pre-tensioned bolts
These bolts are installed using calibrated torque tools or tension-control systems to ensure proper clamping force.
Compared to riveting, bolted connections offer several advantages:
Faster installation
Reduced labour requirements
Easier inspection
Ability to disassemble if necessary
Bolted connections are now the standard in steel buildings, bridges, and industrial structures.
Welding in Modern Steel Fabrication
Another major advancement in structural steel construction is welding.
Welding allows steel components to be fused together directly, creating continuous connections without the need for fasteners.
Welded connections provide:
High structural strength
Smooth load transfer
Clean structural appearance
However, welding requires strict quality control and inspection procedures to ensure safety and reliability.
In many projects, engineers use a combination of welding and bolting to achieve the best performance.
Lessons from the Eiffel Tower’s Rivets
Despite the rise of modern connection systems, the rivets in the Eiffel Tower remain a testament to the craftsmanship and engineering skill of the 19th century.
More than 130 years after its construction, those 2.5 million rivets continue to hold the structure together safely.
The tower demonstrates several key lessons for modern engineers and fabricators:
Precision Matters
Even without modern digital tools, Gustave Eiffel’s team achieved remarkable precision in fabrication and assembly.
Skilled Labour Is Essential
The riveting teams required coordination, timing, and expertise to install each fastener correctly.
Structural Connections Are Critical
Strong connections are essential to the overall performance of any steel structure.
Why the Eiffel Tower’s Rivets Still Matter Today
Although modern construction has moved beyond traditional riveting, the Eiffel Tower remains one of the greatest examples of riveted engineering ever built.
Every rivet tells the story of a time when large structures were assembled through skill, craftsmanship, and human coordination.
Today, engineers rely on advanced materials, digital modelling, and high-tech fabrication methods.
Yet the core principle remains unchanged:
Strong structures depend on strong connections.
Whether those connections are rivets, bolts, or welds, the success of any steel structure ultimately lies in how its components are fastened together.
And the Eiffel Tower stands as one of the greatest demonstrations of that principle ever built.
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