What are floor joist supports called?

Demystifying Floor Joist Supports: What Are They Called?

Brief Summary

Floor joists are commonly supported by several key components, each with a specific role in ensuring structural integrity. These supports include beams, girders, joist hangers, ledger boards, and even foundation walls in certain cases.

Expanded Answer

Beams and Girders: Primary Load-Bearing Members

• Beams: Horizontal structural members that span between supports like columns or walls, carrying the load of the joists.
• Girders: Larger, primary beams that support multiple beams and transfer their combined load to the foundation or columns.
• Key Points:
  • Beams and girders are crucial for distributing the weight of the floor and its contents to the foundation.
  • Their size and spacing depend on factors like the span, load requirements, and the type of joists used.
  • They can be made of various materials like wood, steel, or concrete.

Joist Hangers: Connecting Joists to Beams

• Function: Joist hangers are metal connectors that securely fasten the ends of joists to beams or ledger boards. They provide critical support and prevent joists from twisting or slipping.
• Types:
  • Face-Mount Hangers: Attach to the side of the beam.
  • Top-Mount Hangers: Sit on top of the beam.
  • Concealed Flange Hangers: Offer a hidden connection for a cleaner look.
• Key Points:
  • Joist hangers are essential for ensuring a strong and stable connection between joists and supporting beams.
  • They come in various sizes and configurations to accommodate different joist dimensions and load requirements.
  • Building codes mandate their use and proper installation for safety.

Ledger Boards: Supporting Joists at the Wall

• Function: A ledger board is a horizontal board attached to the house or building wall, providing support for one end of the joists.
• Placement: Typically installed parallel to the floor joists, ledger boards are securely anchored to the wall using appropriate fasteners.
• Key Points:
  • Ledger boards offer a convenient way to support joists where they meet the exterior wall of a building.
  • Proper attachment to the wall is crucial for structural integrity and safety.

Foundation Walls: Direct Support

• Function: In some cases, particularly in basements or crawl spaces, floor joists may rest directly on top of the foundation walls, eliminating the need for beams or girders.
• Key Points:
  • The foundation wall must be properly designed and constructed to support the load of the joists and the floor above.
  • This method may require additional support in the form of pilasters or columns for longer spans.

Current Trends & Considerations

• Engineered Wood Products: I-joists and open-web trusses are increasingly used for their strength, stiffness, and longer span capabilities, reducing the need for intermediate beams or support posts.
• Seismic Design: In earthquake-prone regions, specialized joist hangers and connectors are used to enhance the structural resilience of the floor system.
• Energy Efficiency: Building codes increasingly emphasize energy efficiency, impacting insulation requirements around joist and beam connections.

Conclusion

Floor joists rely on a network of supporting elements, including beams, girders, joist hangers, and ledger boards, to ensure structural stability and safety. Understanding these components and their proper installation is vital for constructing a sound and code-compliant floor system.