How Strong Are Metal Gusset Plates? We Put Them to the Test
When you look at a manufactured roof truss, one of the smallest components can also be one of the most important: the metal gusset plate.
These thin metal plates connect individual pieces of lumber, helping them work together as an engineered structural system. Without properly designed connections, manufactured roof trusses wouldn't be able to achieve the impressive spans they're known for.
But just how strong are these little plates?
At Truss Components of Washington, we decided to demonstrate their strength with the help of our sales representative, Vince. Standing at 6 feet 7 inches tall and weighing 260 pounds, Vince was the perfect person to put one of these connections to the test.
The results demonstrated not only the strength of a properly loaded connection, but also why the direction of an applied load matters.
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What Are Metal Gusset Plates?
Metal gusset plates, also commonly called metal connector plates or gang nail plates, are used to connect pieces of lumber in manufactured wood trusses.
If you've ever looked closely at a roof truss, you've probably noticed the rectangular metal plates located where two or more pieces of lumber meet.
These plates have numerous small teeth that embed into the wood, creating a mechanical connection between the individual members.
Unlike traditional framing methods that may rely on individual nails or other fasteners, manufactured trusses use engineered metal connector plates to join the lumber at specific locations.
Each connection plays an important role in helping the truss transfer forces throughout its structure.
How Do Metal Gusset Plates Work?
The strength of a metal gusset plate comes from the way its teeth engage with the lumber.
During truss manufacturing, the plates are pressed into the wood using specialized equipment. The teeth penetrate the lumber and create a connection designed to transfer forces between the adjoining pieces.
However, the plates aren't simply placed wherever they fit.
Their size, placement, and orientation are determined during the truss design and engineering process.
Engineers consider several factors when designing these connections, including:
The forces acting on the joint
The size and type of lumber being connected
The configuration of the truss
The required strength of the connection
The direction of the forces being transferred
This is one reason why metal gusset plates are such an important part of modern truss manufacturing.
When properly designed and installed, these connections allow individual pieces of lumber to function together as part of a larger structural system.
Putting Metal Gusset Plates to the Test
To demonstrate how these connections behave under different loading conditions, Vince joined two pieces of 2x4 lumber using a 3-by-6-inch metal gusset plate.
This type of connection is called a splice.
A splice allows two pieces of lumber to be joined together, transferring forces through the connection.
For our demonstration, we wanted to see how the assembly would respond to Vince's 260 pounds under two different orientations.
Test 1: Loading the Lumber Upright
For the first demonstration, the connected lumber was positioned with the wider dimension of the 2x4 oriented vertically.
Vince applied his weight to the test assembly, and the connection held.
The demonstration showed how the assembly could support the applied load in that particular orientation.
But there was an important reason for this result.
With the lumber upright, the assembly had greater bending resistance than it would when positioned flat. The connection and the lumber were also being loaded in a different direction relative to the plate.
This is an important distinction because the performance of a structural connection depends on more than the strength of the metal plate alone.
Test 2: Loading the Lumber on Its Side
For the second demonstration, Vince rotated the connected lumber onto its thinner side.
He then applied his weight again.
This time, the assembly experienced a dramatic failure.
The lumber split, and the metal gusset plate connection was damaged.
Although the same general connection was being tested, changing the orientation significantly changed how the assembly responded to the applied load.
This demonstrates an important principle in structural engineering: the direction of a load can dramatically affect how a structural member or connection performs.
The demonstration was an informal comparison of two loading arrangements, not a standardized strength test or a measurement of the rated capacity of the connector plate.
Why Truss Orientation Matters
Manufactured roof trusses are engineered to carry specific loads through a carefully designed arrangement of lumber and metal connector plates.
In their intended orientation, the members and connections work together to transfer forces through the truss.
However, roof trusses also require proper handling, installation, lateral restraint, and bracing to remain stable.
Loads applied outside the intended plane of a truss can create additional stresses and instability, especially when the truss is not adequately supported or braced.
This is why builders and installers must pay attention to manufacturer instructions and the project's engineered truss documents.
Proper installation is about more than simply placing a truss in the correct location. It also involves ensuring the truss is supported, restrained, and braced as required.
Our demonstration with Vince provides a visual reminder that even a strong engineered connection can behave very differently when the loading conditions change.
How Metal Gusset Plates Help Roof Trusses Span Long Distances
One of the greatest advantages of engineered roof trusses is their ability to span substantial distances while efficiently using lumber.
At Truss Components of Washington, we manufacture roof trusses for a wide variety of residential and commercial applications, including designs with spans reaching up to 60 feet.
These capabilities come from the combined performance of several important elements:
Truss geometry: The arrangement of chords and webs helps distribute forces throughout the structure.
Engineered lumber members: Each piece is selected and designed for its structural role.
Metal gusset plates: The connections help transfer forces between adjoining members.
Engineering and design: The entire truss is designed to meet the requirements of the specific project.
Metal gusset plates are essential to this process, but they are only one part of what makes an engineered roof truss effective.
It's the combination of the design, lumber, connections, and proper installation that makes the system work.
Why You Should Never Modify a Truss Without Approval
Because metal gusset plates and the surrounding lumber are engineered to work together, changes to a manufactured truss can affect its structural performance.
Cutting a truss member, removing a plate, drilling through a connection, or otherwise altering the original design can interfere with the way forces are transferred through the structure.
If a truss needs to be modified or repaired, the appropriate course of action is to contact the truss manufacturer or a qualified design professional for an approved solution.
Even changes that appear minor can affect the integrity of the overall system.
Small Plates, Big Responsibility
Metal gusset plates might not look particularly impressive at first glance, but they're essential components in manufactured roof trusses.
Vince's demonstration showed how a connection can perform successfully under one loading arrangement and fail under another.
The takeaway isn't simply that metal gusset plates are strong. It's that their strength and performance depend on proper engineering, installation, and loading conditions.
Next time you see a manufactured roof truss, take a closer look at those small metal plates connecting the lumber.
They're doing more work than you might think.
Looking for an Experienced Roof Truss Manufacturer?
At Truss Components of Washington, we've been manufacturing engineered building components for builders throughout Western Washington since 1992.
We specialize in engineered roof trusses, floor trusses, and prefabricated wall panels designed to help builders frame their projects efficiently.
Whether you're working on a residential home or a larger commercial project, our team can help you find the right component solution.
Contact Truss Components of Washington to discuss your next project or request a quote.