Steel Joist Design

Precise Steel Joist Design

Global Engineering Solutions by Consac. SJI-Compliant. Serving the USA, Canada, Australia, and beyond.

Our expert team delivers end-to-end steel joist and joist girder solutions, ensuring structural integrity, cost-efficiency, and compliance with international standards. We provide detailed analysis, BIM modeling, and certified drawings for every project. Trust Consac for reliable, innovative, and cost-optimized steel joist engineering worldwide.

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Key Concepts

We provide end-to-end steel joist and girder solutions, ensuring structural integrity, cost-efficiency, and full compliance with international standards.

Structural Design & Analysis

Comprehensive design services for open web steel joists (K, LH, DLH), joist girders (G), and composite joists (CJ). We utilize cutting-edge software to perform detailed analysis, ensuring all designs meet or exceed SJI, CISC, and AS standards. Our calculations account for all specified loads, including dead, live, snow, wind, and seismic.

BIM Integration & Detailing

We deliver fully constructible 3D models and 2D shop drawings. Our BIM (Building Information Modeling) process ensures seamless coordination with architects, MEP, and other trades, preventing clashes and streamlining the construction process. We provide precise joist placement plans, bridging diagrams, and detailed connection designs.

Global Standards Compliance

Consac has dedicated expertise in navigating the specific requirements of various international codes. Whether your project is in the United States (SJI/AISC), Canada (CISC S16), or Australia (AS 4100), our registered engineers will stamp and seal drawings, ensuring full regulatory compliance for your jurisdiction.

Interactive Joist Catalog

Explore the specifications and applications of common SJI-designated steel joists. This information is illustrative; all designs must be professionally engineered for your specific project loads and conditions.

K-Series Joists

K-Series Joists are the most common type, used for light-to-medium loads on spans up to 60 feet (18.3m). They are standardized in depths from 8 inches to 30 inches. These joists are ideal for standard roof and floor construction in commercial buildings, schools, and retail centers.

Key Specifications (per SJI):

Depths: 8" (203mm) to 30" (762mm)
Spans: Up to 60' (18.3m)
Webs: Single round bar, bent to form a Warren truss.
Connections: Typically 2.5" (64mm) end-bearing depth.
Bridging: Requires horizontal or diagonal bridging rows as specified in SJI tables.

The K-Series designation is straightforward, e.g., a "24K10" is a 24-inch deep K-Series joist with a chord size designated as "10". Our engineers select the most economical joist based on the required span, load, and deflection criteria. We provide detailed layouts showing the precise location and mark for every joist.

LH-Series Joists (Longspan)

LH-Series (Longspan) Joists are designed for heavier loads and longer spans, ranging from 25 feet up to 100 feet (30.5m). They are standardized in depths from 18 inches to 48 inches. These are commonly used in large open spaces like gymnasiums, auditoriums, and industrial facilities.

Key Specifications (per SJI):

Depths: 18" (457mm) to 48" (1219mm)
Spans: Up to 100' (30.5m)
Webs: Can be single round bars or double angles, depending on load.
Connections: Typically 5" (127mm) end-bearing depth.
Bridging: Requires robust horizontal and/or diagonal bridging.

LH-Series joists can be specified with either parallel chords or single-pitched top chords for roof drainage. Our design team will specify the required bridging and connection details to ensure the stability of these long-span members.

DLH-Series Joists (Deep Longspan)

DLH-Series (Deep Longspan) Joists are intended for the heaviest loads and the longest spans, from 80 feet up to 144 feet (43.9m). Depths range from 52 inches to 72 inches. These are heavy-duty structural elements used in arenas, convention centers, and hangars.

Key Specifications (per SJI):

Depths: 52" (1321mm) to 72" (1829mm)
Spans: Up to 144' (43.9m)
Webs: Typically double-angle members.
Connections: Typically 7.5" (191mm) end-bearing depth.
Bridging: Requires extensive, engineered bridging systems.

Design of DLH-Series joists is a complex task involving careful consideration of handling, erection stability, and permanent bracing. Our team provides complete design and detailing for the entire system, including primary girders and columns.

CJ-Series Joists (Composite)

CJ-Series Joists are designed to act compositely with a concrete slab, creating a stiff and robust floor system. Shear studs are welded to the joist's top chord, which then bond with the concrete. This system is excellent for minimizing floor vibrations and is common in multi-story office buildings, hospitals, and laboratories.

Key Features:

Action: Joist and slab work as a single unit.
Benefit: Increased stiffness, reduced vibration, shallower floor depths.
Design: Requires careful calculation of composite section properties.
Application: Floors requiring superior vibration control.

Consac's engineers are proficient in composite design, specifying the required shear stud count, concrete strength, and joist properties to meet your project's specific floor performance criteria (e.g., vibration-sensitive lab equipment).

Composite Action

Shear studs on the top chord (represented by circles) bond with the concrete slab (represented by the top block) to form a unified, stronger system.

Joist Girders (G-Series)

Joist Girders (G-Series) are not joists themselves, but primary structural members designed to support other joists. They are open-web trusses, just like joists, but are engineered to carry the concentrated loads from the joists that frame into them. They are an economical alternative to wide-flange beams.

Key Features:

Function: Primary framing member, supports joists.
Design: Engineered for specific, non-uniform point loads.
Spans: Typically 20' to 60' (6m to 18m).
Benefit: Lighter weight than solid beams, allows for MEP pass-through.

Consac designs the entire roofing or flooring system, including the optimal layout and design of Joist Girders to support the K, LH, or DLH joists. We provide a complete framing plan that is both economical and easy to erect.

Typical Joist Girder System

JOIST GIRDER (G)

Joist (K)

The Joist Girder (Green) acts as a beam, supporting the ends of the secondary Joists (Orange).

Technical Information Center

Our design philosophy is rooted in the rigorous application of established engineering principles and standards. This information is for educational purposes and is not a substitute for a professional engineer's analysis.

Standards & Compliance: Our Foundation

All engineering work performed by Consac is executed in strict accordance with the prevailing building codes and industry standards for the project's jurisdiction. Our commitment to compliance is non-negotiable and is the cornerstone of our quality assurance.

For projects in the United States:

Steel Joist Institute (SJI): We adhere to the SJI's "Standard Specifications for Open Web Steel Joists" (K, LH, DLH, CJ) and "Standard Specifications for Joist Girders" (G-Series). This includes all provisions for design, loading, bridging, and connections.
American Institute of Steel Construction (AISC): All connections, member designs (where not covered by SJI), and overall structural behavior are checked against the AISC "Specification for Structural Steel Buildings" (AISC 360).
American Society of Civil Engineers (ASCE): All load calculations (dead, live, snow, wind, seismic) are derived from ASCE 7, "Minimum Design Loads and Associated Criteria for Buildings and Other Structures."
Building Codes: Our designs are compliant with the International Building Code (IBC) or any local code amendments.

For projects in Canada:

Canadian Institute of Steel Construction (CISC): We follow the CISC "Code of Standard Practice" and design according to CAN/CSA-S16, "Design of Steel Structures."
National Building Code of Canada (NBCC): All loads and structural requirements are based on the latest edition of the NBCC.

For projects in Australia:

Standards Australia: Designs are performed in accordance with AS 4100, "Steel Structures," and AS/NZS 1170 for load calculations.

Our team includes licensed Professional Engineers (P.E.) in the US, Professional Engineers (P.Eng.) in Canada, and Chartered Professional Engineers (CPEng) in Australia, enabling us to provide certified, sealed drawings for your project, wherever it is.

The Critical Role of Joist Bridging

Bridging is one of the most critical components of a steel joist system, yet it is often misunderstood. Its primary purpose is to provide lateral stability to the joist chords during erection and to brace the compression chord against buckling once the structure is in service.

1. Erection Stability:

Steel joists are very slender and unstable in the lateral (sideways) direction until they are properly braced. Bridging connects multiple joists together, creating a stable system that can resist tipping and lateral movement. SJI specifies the maximum unbraced length of a joist chord during erection, which dictates the placement of "bridging for erection." This is a life-safety issue for ironworkers.

2. In-Service Bracing (Compression Chord):

Once under load, a joist's top chord is typically in compression (like a column). This compression force makes it want to buckle sideways. Bridging, in conjunction with the roof or floor deck, provides the bracing force to prevent this buckling, allowing the chord to achieve its full strength. The required number of bridging rows is determined by the joist span, chord size, and load.

Types of Bridging:

Horizontal Bridging: Typically angles or channels running horizontally between the top and bottom chords. This is common for K-Series joists.
Diagonal Bridging: Consists of a series of angles or rods in an X-pattern between adjacent joists. Required for most LH- and DLH-Series joists, and for K-Series with large spans or heavy loads.
Gusset Plate Bridging: Used for heavier applications and is designed as a custom truss system.

Consac provides a detailed Bridging Plan, ensuring compliance with all SJI spacing and connection requirements. Correct bridging is paramount for structural safety.

Joist Connection Details

The connection of the joist ends to the supporting structure (beams, girders, or columns) is a critical design element. These connections must transfer the vertical reactions (shear) and often resist lateral forces (wind or seismic).

Common Connection Types:

Standard End Bearing: The bottom chord is welded to a bearing plate on the support. The size of the weld is engineered based on the reaction force.
Sloped Connections: For roof systems requiring pitch, the end bearing is designed to match the required slope, ensuring proper drainage.
Moment Connections: While joists are typically designed as simply supported members (no moment transfer), our team can design specialty connections for small moment transfer or where required for lateral stability.

All Consac shop drawings include clear, detailed connection marks and welding specifications to ensure accurate and safe fabrication and erection.

Materials & Coatings Specifications

The materials used in the fabrication of steel joists and girders are carefully selected to meet the structural demands and environmental exposure of the project.

Steel Materials:

Chords & Webs: Typically utilize steel conforming to ASTM A36, ASTM A529 Gr. 50, or ASTM A572 Gr. 50, depending on the required strength and jurisdiction.
Shear Studs: For Composite Joists (CJ), studs are per ASTM A108.

Finishes and Coatings:

Standard Finish: A shop coat of standard grey primer paint is applied to protect against atmospheric corrosion during shipment and erection.
Galvanizing: For exposed or highly corrosive environments (e.g., coastal areas or water treatment plants), we can specify hot-dip galvanizing per ASTM A123.

All materials and finishes are clearly specified in our drawings to ensure the fabrication process meets the long-term durability requirements of your structure.

Why Choose Consac for Your Project?

Our unique combination of experience, compliance expertise, and advanced technology sets us apart as the global leader in steel joist engineering.

Multi-Jurisdictional Certification

Unlike many firms, Consac holds P.E./CPEng licenses in all major regions (USA, Canada, Australia). This ensures your drawings are legally compliant and stamp-ready wherever you build.

Rapid Turnaround & Accuracy

Our proprietary joist design software and disciplined BIM workflow dramatically reduce lead times without compromising accuracy, getting your fabrication started faster.

Cost Optimization Focus

Every design includes a free Value Engineering (VE) review, often identifying opportunities to reduce steel tonnage or simplify fabrication, translating directly into project savings.

Frequently Asked Questions

Get quick answers to the most common questions about steel joist design, compliance, and our engineering process.

What information do you need to start a design?

To provide an accurate quote and design, we ideally need:

Architectural plans (for roof/floor geometry).
Structural plans (showing supporting beams, columns, and walls).
Project location (for code, snow, wind, and seismic loads).
Required live loads (e.g., 50 psf for office, 100 psf for storage).
Any large rooftop units (HVAC) or other concentrated loads.
Desired floor performance (e.g., for vibration-sensitive areas).

How long does the design and detailing process take?

This depends on the project's size and complexity. A small, straightforward retail building might take 1-2 weeks for sealed design drawings. A large, complex hospital wing with composite joists and heavy MEP coordination could take 4-6 weeks or more. We will provide a firm schedule with our proposal.

Do you also fabricate the joists?

No, Consac is a specialized design and engineering firm. We do not fabricate materials. We provide the detailed, sealed shop drawings and calculations that a steel fabricator (an SJI-member manufacturer) uses to build the joists. This separation of design and fabrication allows us to be an objective, independent partner focused solely on the best engineering solution for *your* project.

What is the difference between a joist and a joist girder?

Think of it in two levels. Joists (like K or LH-Series) are the "secondary" members. They are closely spaced (e.g., 4-6 feet apart) and directly support the roof or floor deck. A Joist Girder (G-Series) is a "primary" member. It is a large, heavy-duty truss designed to support the *ends* of the joists and transfer their load to the columns. You will have many joists, but only a few joist girders.

Can I cut a hole in a steel joist web for a pipe?

You must never cut, weld, or modify a joist in any way without explicit, written approval from a qualified engineer. The web members of a joist are critical to its strength. Cutting a web member, even a small one, can lead to a catastrophic failure.
If a penetration is needed, it must be designed *beforehand*. We can design the joist with a special "clear opening" (a "V" or "box" opening) that is reinforced to safely allow for MEP pass-through. If a modification is needed in the field, you must contact us immediately so we can engineer a safe, SJI-approved reinforcement detail.