What is the difference between stringers and joists?
Stair Joists vs. Stringers: Clearing the Confusion
Brief Summary
While the terms “joist” and “stringer” are sometimes used interchangeably, they represent distinct structural elements with specific applications. Joists are horizontal framing members used primarily in floors and ceilings, while stringers are the inclined, load-bearing boards that support the treads and risers of a staircase.
Expanded Answer
Joists: The Foundation of Floors and Ceilings
- Function: Joists are horizontal beams that span between supporting walls or beams, forming the framework for floors and ceilings. They bear the weight of the structure above, including floor coverings, furniture, and occupants, distributing the load to the foundation.
- Orientation: Joists are typically installed horizontally, running parallel to each other at regular intervals.
- Material: Joists are commonly made of wood (dimensional lumber or engineered wood like I-joists), but steel or concrete can also be used in certain applications.
Stringers: The Backbone of Staircases
- Function: Stringers are the inclined members that support the treads (horizontal steps) and risers (vertical boards between treads) of a staircase. They transfer the weight of the stairs and its users to the floor or supporting structure.
- Orientation: Stringers are angled to match the slope of the staircase, running along its sides or, in some cases, centrally beneath the treads.
- Types:
- Cut Stringers: Feature notches cut into them to accommodate the treads and risers.
- Closed Stringers: Have routed grooves to house the treads and risers, offering a more streamlined appearance.
- Mono Stringer: A single, central stringer supports the staircase from underneath, creating a visually open design.
- Material: Similar to joists, stringers are often made of wood, but metal (steel or aluminum) is becoming increasingly popular, especially in modern designs.
Why the Confusion?
- Similar Function: Both joists and stringers are structural elements that provide support and load distribution.
- Interchangeable Use (in some cases): In certain contexts, like when referring to deck stairs, the term “joist” might be used casually to describe the stringers. However, technically, “stringer” is the more accurate term for the inclined support members of a staircase.
Building Code Considerations
- Structural Integrity: Both joists and stringers must be designed and installed according to building codes to ensure adequate strength and safety. These codes specify factors like dimensions, material strength, and attachment methods based on the anticipated loads and span.
- Inspections: Building inspectors will verify compliance with these codes during construction or renovations.
Conclusion
Understanding the distinction between joists and stringers is crucial for clear communication and proper construction practices. While both are essential structural components, they have distinct roles in different parts of a building. Remember, stringers are the angled boards that form the backbone of a staircase, while joists provide horizontal support for floors and ceilings.