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3 October 2023

The Difference Between Flitched Beams and Flitch Plates

Flitched beams and flitch plates are two types of structural steel elements used in construction, but they differ in their composition, manufacturing process, and applications.

Flitched beams are composite steel beams made from two or more layers of wood or wood-based materials, such as plywood or oriented strand board (OSB). These layers are glued together along their longitudinal edges. Steel fabricators usually place layers at a 90-degree angle to each other. This creates a strong and rigid steel structure that resists bending and twisting forces. Flitched beams are commonly used in roof and floor constructions, as well as in wall frames, due to their strength, stiffness, and resistance to rotational forces.

In contrast, a flitch plate is a thin, rectangular steel plate. It’s made of a single layer of wood or wood-based material. Unlike the beams, flitch plates do not consist of multiple layers and are not designed to resist rotational forces. Instead, steel fabricators typically use them as spacers or filler pieces in frame constructions. This provides additional support and stability between vertical studs or joists.

Benefits and drawbacks of using flitched beams and flitch plates

One of the main advantages of flitched beams over flitch plates is their ability to withstand moment loads. Moment loads occur when a force is applied perpendicular to the beam’s longitudinal axis, causing it to rotate. The beams can absorb these forces thanks to their composite nature, which distributes the load across multiple layers. In contrast, flitch plates lack this capability and would likely fail under moment loads.

Another benefit of the beams is their reduced material usage compared to solid sawn timber beams. By using multiple layers of engineered wood products, flitched beams can match the strength and rigidity of larger, solid beams while minimising waste and environmental impact. Moreover, flitched beams offer greater design flexibility, allowing builders and architects to tailor them to specific project requirements.

While beams may seem like the superior choice, flitch plates still have their place in certain applications. When space constraints exist, flitch plates can provide additional support without adding bulk to the structure. They also serve as a convenient nailing surface for finish materials like drywall or paneling, making them suitable for interior use. Additionally, flitch plates tend to be less expensive than flitched beams, which can be an attractive feature for budget-conscious projects.

In summary, flitched beams and flitch plates differ significantly in terms of their composition, functionality, and cost-effectiveness. Beams excel in load-bearing applications that require strength, stiffness, and moment resistance. At the same time, flitch plates find utility in non-load bearing uses where space efficiency and affordability are paramount. Understanding the distinction between these two structural elements enables builders and designers to make informed decisions and create safe, efficient, and economical buildings.

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