When planning roof or floor framing, choosing the correct wood trusses is crucial for structural integrity, cost-efficiency, and practical design. Two widely used types of bearing trusses are Top Chord Bearing trusses (TCB) and Bottom Chord Bearing trusses (BCB), each serving distinct purposes depending on construction needs.
Learn what sets these types of trusses apart, explore their structural features and applications, and help you decide which one suits your project best.
What Are Roof Truss Chords?
Understanding a wood truss starts with its main members:
- Top Chord: This is the upper beam that supports roofing materials and carries loads into the structure.
- Bottom Chord: The lower member, typically functioning as a ceiling joist or supporting the interior finish.
The distinction between TCB and BCB lies in which chord transfers weight to the walls or underlying supports.
What is a Top Chord Bearing (TCB) Truss?
A top chord-bearing truss transfers its load through the top chords. The ends of the top chords rest directly on load-bearing walls or beams. This means the roof load, including materials and external forces like snow or wind, is supported by the walls underneath.
Typical Uses
TCB trusses are most often employed when:
- Construction includes load-bearing walls positioned under truss ends
- Roofing frames are straightforward and economical
- Projects use light commercial or standard residential designs
Key Advantages
- Simplified wall framing by aligning roof support with walls
- Faster assembly, since special support systems are unnecessary
- Lower overall cost, due to fewer engineered beams or complex framing elements
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What is a Bottom Chord Bearing (BCB) Truss?
BCB trusses carry loads via their bottom chords. In this case, the bottom chord ends rest on beams, girders, or designated walls, transferring weight down through that member instead of through the top chord.
Typical Uses
BCB trusses are particularly useful when:
- Floor systems require wide, unobstructed spans
- Interiors feature open plans with fewer structural walls
- Roof layout doesn’t allow interior bearing points beneath trusses
Key Advantages
- Ability to span larger areas without columns or load-bearing walls
- Greater freedom in interior layout thanks to open floor design
- Versatility for use in both flooring and complex roof framing
Key Structural Differences Between TCB and BCB
| Feature | Top Chord Bearing (TCB) | Bottom Chord Bearing (BCB) |
| Load Path | Loads enter through the top chord into supporting walls | Loads enter through the bottom chord into the beams |
| Wall Support | Requires walls or beams under the top chord | Supports can be in interior beams or walls |
| Span Capabilities | Limited by the distance between bearing walls | Capable of much wider spans |
| Ceiling Setup | Bottom chord spans freely and often supports the ceiling | Bottom chord carries load and may need added framing |
| Best Use Case | Typical residential and light commercial projects | Warehouses, large open areas, or flexible interior designs |
How to Choose the Right Truss
Opt for Top Chord Bearing (TCB) Trusses When:
- Your building design includes load-bearing walls directly positioned under the ends of the trusses, providing natural support points.
- You prefer a straightforward and cost-effective framing solution that simplifies construction and reduces material expenses.
- Roof spans are relatively short, and wall placements align well with truss bearing points, ensuring efficient load transfer.
Opt for Bottom Chord Bearing (BCB) Trusses When:
- Creating large, open interior spaces without load-bearing walls is a priority, such as in commercial buildings or modern residential designs.
- Your project requires long, clear spans that can’t be supported by walls alone, offering greater flexibility in room layout and use.
- Flexible interior design is important, allowing for minimal structural walls and maximum usable space.
Installation and Design Notes
Top chord bearing trusses demand accurate wall construction; any misalignment or weak support can compromise structural safety.
Bottom chord bearing trusses often require engineered beams or girders, adding complexity but offering greater design flexibility.
Whether using TCB or BCB, collaboration with architects, engineers, and reputable wood truss suppliers is essential to meet building codes and ensure structural integrity.
Check out our blog on how to install roof trusses properly.
How Ranger Truss of Texas Can Support Your Project
Strong structures start with the right support, and that’s where Ranger Truss of Texas comes in. We design and manufacture custom wood trusses built for durability, precision, and performance. Whether you need top chord bearing trusses or bottom chord bearing trusses, our team tailors every solution to meet your project’s unique demands.
Builders, architects, and homeowners trust us for reliable service, expert guidance, and on-time delivery. At Ranger Truss of Texas, we’re not just supplying trusses, we’re helping you build with confidence from the ground up.
Ultimately, both Top Chord Bearing and Bottom Chord Bearing trusses serve specific structural and design purposes. The right choice depends on the unique needs of your project, whether you’re prioritizing modular efficiency or architectural versatility. Understanding their key differences ensures better planning, safer structures, and optimal performance across residential, commercial, and industrial builds.