Joists are horizontal structural members that span between walls, beams, or foundations to support the weight of floors, ceilings, and roofs. They transfer loads to vertical structural elements while providing a framework for finishing materials.

• Typically installed parallel to each other at regular intervals

• Standard spacing: 16" or 24" on center (measured from the center of one joist to the center of the next)

• Critical for preventing deflection and maintaining structural integrity

• Must be sized according to span length and anticipated loads

1. Composition & Dimensions
Solid sawn joists are cut from single pieces of dimensional softwood lumber, typically spruce, pine, or fir.

• Common sizes: 2×6 to 2×12

• Actual dimensions: Approximately 1.5" × 5.5" to 1.5" × 11.25"

2. Applications
Widely used in residential construction, especially in smaller structures and renovation projects.

• Cost-effective for spans under 16 feet

• Readily available at lumber yards and home improvement stores

3. Limitations

• Span limited by available lumber lengths (typically 16–20 feet)

• Susceptible to shrinking, warping, and twisting as the wood dries

• Heavier than engineered alternatives for the same strength

1. Key Features
Engineered joists are constructed with OSB or plywood webs and solid lumber flanges.

• Depth range: 9.5" to 16" (residential)

• Span capacity: Up to 25–30 feet without intermediate support

• Efficient material use: Reduces lumber usage while maintaining strength

• Consistent quality and performance compared to solid dimensional lumber

2. Design Advantages

• Pre-drilled knockouts simplify routing of HVAC, plumbing, and wiring

• Lightweight design reduces labor effort and installation time

• High load-bearing capacity with less deflection over long spans