Metal Joists Span Tables

Metal Studs floor joists used in construction for a house.

US Frame Factory manufactures and sells metal joists/steel framing joists directly into the market. Metal stud joists are floor framing supports made from cold-formed steel. They are a common alternative to traditional wooden floor joists, offering advantages like:

  • Lighter weight: Makes construction and handling easier.
  • Dimensional stability: Won’t warp or twist like wood over time.
  • Pest and fire resistance: Metal isn’t susceptible to termites and doesn’t burn easily.
  • Versatility: They come in various sizes and thicknesses, and their load capacity depends on factors like span and spacing.

Understanding Floor Loads (Live load and dead load)

  • Dead Load: The weight of the permanent structural elements of the floor itself (joists, decking, flooring, etc.).
  • Live Load: Temporary weight on the floor, such as people, furniture, movable items. Building codes establish minimum live load requirements for different uses.

Typical Live Loads for Metal Joists

  • Residential: Usually 40 pounds per square foot (psf). For single family homes.
  • Light Commercial: 50 psf and upwards, depending on the specific use of the space. Multi-family, Hotels, Schools, and Hospitals.
  • Storage Facility: Most building codes specify a minimum live load of 125 pounds per square foot (psf) for light storage areas. Heavier storage may require higher values.

Factors Affecting Load Capacity of steel joists:

  • Joist Size and Gauge: Larger joist sizes with thicker steel gauges increase load capacity.
  • Spacing: Closer joist spacing distributes loads better, increasing capacity.
  • Span: The unsupported distance a joist covers. Longer spans require stronger joists.
  • Deflection Limits: Building codes set limits on how much a floor can bend under load. Stiffer joists are needed to meet stricter deflection limits.

Residential Attic: Metal Joist Span Table.

30 lbs/sf (pounds per square foot) is a typical design load used for residential attics intended for limited storage. Use the table below for guidance on a typical walkable attic in a residential home. Unlike wood construction, it’s always recommended to have steel joists land directly on top of wall studs for optimal support.

Residential, Multi-family, Hotel Floor: Metal Joist Span Table

50 psf (pounds per square foot) is the typical design load used for floor systems in many high-occupancy buildings. This is typically calculated as the sum of two components:

  • Dead load (40 psf): This represents the weight of permanent building elements like the floor structure itself, sheathing, and any non-removable fixtures.
  • Live load (10 psf): This accounts for the weight of people and furniture that will occupy the space.

It’s important to note that this is a general guideline, and the actual load requirements can vary depending on several factors, including:

  • Weight of floor sheathing: Different sheathing materials have different weights.
  • Desired STC (Sound Transmission Class) rating: Specific sheathing materials can help achieve higher sound dampening.

Therefore, selecting the appropriate floor sheathing should consider both load capacity and desired sound transmission performance.

Self-storage: Metal Joist Span Table

Self-storage buildings have a high psf rating of 125 live load and 15 dead load.

Metal Joist used for a second floor platform on a high occupancy building(Church)

Metal Joists vs Trusses/Concrete Floor Systems Cost Comparison

Metal Floor joists are far cheaper than LGS trusses and significantly cheaper than concrete floor systems. Here are the ballpark prices of some common floor systems uninstalled.

  • Metal Floor joists: $4/SF
  • Light Gauge Metal Trusses: $5/SF
  • Hollow-core slab: $11/SF
  • Post Tention Concrete: $15/SF

Metal Joists: Pros and cons

Pros

  • Cheaper than other metal trusses, bar joists, concrete slabs, T-plank, and hollow-core floor systems.
  • Efficient Transporation over long distances, metal joist and be more efficiently packed and transported long distances and in shipping containers. Making metal joists ideal for use in the Caribbean islands.
  • Lower building profiles: while trusses usually at least 18 inches high, metal joists are often only 10″ or 12″. This allows for a lower building profile overall.
  • Can be assembled on the ground easily in panels, allowing for compact delivery.

Cons

  • There more expensive than their wood counter part.
  • Sound Transmission: Floors framed with joists can transmit more sound between levels compared to some other framing methods. Insulation can help mitigate this.
  • Span Limitations: The distance a floor joist can span depends on its size and the intended load. This can lead to the need for additional support beams or columns in rooms with wider spans in comparison trusses.
  • Limited space for HVAC lines. Metal joists are typically only 12″ and often their structure is extremely compromised if you drill large holes in them. To combat this many builders, install drop ceilings.

Additional Recourses

Current Metal Stud Pricing

Structural Metal Studs

Metal Trusses

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