What are the boards between joists called?
Demystifying Deck Construction: What are Those Boards Between Joists?
Quick Answer
The boards installed between joists in a deck’s framing are technically called blocking or bridging. Their primary function is to provide lateral stability to the joists, preventing them from twisting or warping under load.
Deeper Dive into Blocking/Bridging
Purpose and Function:
- Lateral Stability: Joists, the horizontal structural members that support the deck’s surface, can be prone to twisting or lateral movement, especially under heavy loads or over time. Blocking acts as a brace, connecting adjacent joists and enhancing their resistance to these forces.
- Load Distribution: In some cases, blocking can also help distribute loads more evenly across the joists, preventing excessive stress on individual members.
- Stiffening the Frame: By tying the joists together, blocking contributes to the overall stiffness and rigidity of the deck frame, reducing deflection and improving the deck’s structural performance.
Installation and Placement:
- Typical Spacing: Blocking is usually installed at intervals of 4 to 6 feet along the span of the joists. This spacing helps ensure adequate support and prevents excessive deflection.
- Zigzag Pattern: It’s common to install blocking in a staggered or zigzag pattern between joists. This pattern provides more effective bracing than straight-line installation.
- Secure Fastening: Blocking should be securely fastened to the joists using appropriate nails or screws. The specific fastening requirements may vary depending on the local building codes and the type of wood used.
Material and Size:
- Common Material: Blocking is typically made from the same type of lumber as the joists, ensuring compatibility and consistent structural performance.
- Size: The dimensions of the blocking will depend on the size of the joists and the specific structural requirements. In general, it’s recommended to use blocking that is at least the same depth as the joists and at least 2 inches wide.
Building Codes and Best Practices:
- Code Compliance: While specific requirements may vary by jurisdiction, most building codes mandate the use of blocking in deck construction. It’s crucial to consult local codes and follow their guidelines regarding blocking placement, size, and fastening.
- Beyond Code Minimums: Even if not strictly required by code, additional blocking can be beneficial in areas of high load or where the joists span long distances. It’s always wise to prioritize safety and structural integrity.
Impact on Remodeling:
- Retrofitting: In existing decks, adding blocking can be a valuable retrofitting measure to improve structural performance and address any existing issues with joist twisting or deflection.
- Enhanced Stability: When remodeling or expanding a deck, incorporating proper blocking during the framing stage ensures a strong and stable foundation for the new structure.
Conclusion
While often overlooked, the boards between joists, known as blocking or bridging, play a vital role in the structural integrity of a deck. They enhance the stability and load-bearing capacity of the joists, contributing to a safe and long-lasting outdoor living space. Whether you’re building a new deck or renovating an existing one, ensure that proper blocking is incorporated in accordance with local building codes and best practices.