The Difference Between Joists and Beams
- Dec 16, 2025
- 3 min read
Updated: Jan 28
As winter tightens its grip in early December 2025, construction projects are in full swing, racing against the clock before the harshest weather sets in. Whether you're a seasoned construction professional or a home builder embarking on a new project, understanding the nuances of framing is paramount. Two critical components of any structure are joists and beams. While both are horizontal structural members, their roles, load-bearing capacities, and installation methods differ significantly. This comprehensive guide will explore the key distinctions between joists and beams, providing you with the knowledge to make informed decisions on your next build as well as how the FASCO (a BECK brand) F70G Joist Hanger Nailer can help.
Defining Joists
Joists are the unsung heroes of floor and ceiling systems. These horizontal framing members run between beams or the top plates of walls, forming the backbone that supports floors and ceilings. Think of them as the slats of a bed frame, distributing weight evenly. Unlike beams, joists work in concert, sharing the load-bearing burden across a unified system.
In residential construction, you'll encounter floor joists and ceiling joists. Floor joists support the weight of floors, occupants, and furniture. Ceiling joists, on the other hand, bear the load of roofing materials, insulation, and potential snow accumulation.
The most commonly used lumber for joists is 2×6, though 2×8, 2×10, and 2×12 sizes are also widely used. Engineered wood I-joists are gaining popularity, offering superior span capabilities, dimensional consistency, and reduced susceptibility to warping. Standard joist spacing is often 16 inches on center, although advanced framing techniques increasingly utilize 24-inch spacing for I-joists to reduce lumber use while maintaining structural integrity.
Defining Beams
Beams are the heavy lifters of the structural world. It’s a structural element that primarily resists loads applied laterally across its axis. They serve as the primary load-bearing members, supporting multiple joists and transferring concentrated loads to columns, bearing walls, and ultimately, the foundation.
Historically, beams were squared timbers. Today, they can be made of steel I-beams, laminated veneer lumber (LVL), glulam beams, or engineered wood products. To understand the difference, think of that bed frame again—both the beams and the slats are horizontal members (meaning they run parallel to the ground), but beams are larger, and the beams are what support the slats. Beams primarily carry vertical gravitational forces, but they can also handle horizontal loads from wind or earthquakes.
Beams are classified based on their support conditions, such as simply supported, fixed, overhanging, or cantilever beams. In residential construction, simply supported and continuous beams are most common. Sizing and material selection involve complex engineering calculations.
Key Differences Between Joists and Beams
The distinctions between joists and beams are multifaceted, encompassing load-bearing capacity, dimensions, support mechanisms, and connection requirements. Beams are usually larger and thicker since they bear more weight, and joists are smaller and appear in greater numbers in both floor and roof applications. Joists distribute the load evenly across the beams, which then transfer it to weight-bearing walls or foundational supports.
While joists are typically spaced 16-24 inches on center, beams are spaced several feet apart. A house has a few beams and many joists—girders and beams support loads down through posts and bearing walls, into a home's foundation. Beams sit on the foundation or concrete piles for support, while joists connect to beams and rely on them for support.
Connection methods also differ. Joists are often face-nailed or attached using joist hangers. Joist hangers provide strong, secure, and easy-to-install connections between joists and beams in construction, which is crucial for preventing sagging and ensuring structural stability. Beams can have fixed, cantilevered, or overhanging ends, influencing how they transfer loads.
FASCO® F70G Joist Hanger Nailer
Modern tools like our F70G Cordless Joist Hanger Nailer are revolutionizing framing installation. The F70G is cordless, drives 1-1/2" to 2-1/2" nails, has single-shot firing, adjustable depth, and a dry-fire lockout, using a fuel cell and battery. This tool is
hangers, ensuring precise placement and full penetration into supporting members. Paired with our joist hanger or anchor nails, your sure to have a quick secure connection every time!
Understanding the difference between joists and beams is crucial for any construction professional. Joists distribute loads across a structure, while beams bear the brunt of the weight, transferring it to the foundation. As you plan your next project this December, remember these key distinctions to ensure structural integrity and safety.
