What's The Difference Between A TS And An HSS? - Atlas Tube

Have you ever looked at a set of structural drawings and wondered about the difference between “TS” and “HSS”? If you’ve been in the industry for a while, you likely remember when Tube Steel (TS) was the standard term in the United States. Today, Hollow Structural Section (HSS) is the globally recognized name. This article explains the history behind this change, clarifies the terminology, and provides an updated look at current industry standards for 2025. 

This article will cover the key reasons for the industry’s shift, what it means for specifications today, and how to ensure the steel sections you design with are readily available. 

The Shift from TS to HSS: A Brief History 

For decades, professionals in the U.S. referred to closed rectangular, square, or round steel profiles as Tube Steel, or TS. These sections were, and still are, primarily manufactured according to the ASTM A500 specification. In Canada, the equivalent standard is CSA G40. The term was so ingrained that the industry’s promotional body was named the Steel Tube Institute. 

However, outside of the United States, the terminology was different. In Canada, Europe, and Asia, these products were known as Hollow Structural Sections (HSS). You might also encounter regional variations like: 

• SHS: Square Hollow Section 

• RHS: Rectangular Hollow Section 

• CHS: Circular Hollow Section 

This difference in naming created a need for a common language as engineering and construction became more global. 

Aligning with Global Standards 

In the early 1990s, the American Institute of Steel Construction (AISC) made a strategic decision to align U.S. terminology with the rest of the world. This transition officially began in 1998 with the second edition of the AISC LRFD Steel Construction Manual. 

In this influential guide, AISC established “Hollow Structural Section” as the correct designation for these profiles. This change helped standardize communication among engineers, fabricators, and suppliers worldwide, reducing confusion and improving collaboration on international projects. The move was further cemented by the joint publication of the HSS Connections Manual by AISC and the Steel Tube Institute. 

HSS vs. Pipe: A Common Point of Confusion 

It’s important to distinguish HSS from steel pipe. While HSS and pipe can look similar, they are products manufactured to different specifications and intended for different applications. 

HSS is produced to meet structural engineering tolerances and specifications, such as ASTM A500, ASTM A1085, or ASTM A1065. It is designed for use as a structural element in buildings, bridges, heavy equipment, and other applications. 

Pipe, on the other hand, is typically manufactured to specifications like ASTM A53. It is designed primarily to transport fluids or gases. Its dimensional tolerances and structural properties are not as tightly controlled as those for HSS, making it unsuitable for most structural applications. 

Navigating HSS Availability in 2025 

A common question that arises, especially for engineers referencing older plans, is: “Why can’t I find certain TS sizes anymore?” The answer is that the steel industry has evolved. Over the years, manufacturing capabilities have advanced, and market demand has shifted. Some sizes that were common decades ago are no longer produced. 

If you are working from an older edition of the AISC Steel Construction Manual, you may encounter sizes that are now obsolete. To avoid specifying a section that is difficult or impossible to source, it’s crucial to verify its availability. 

How to Check for Current HSS Sizes 

The AISC provides an invaluable resource with its Steel Availability database. This tool helps you see which producers might manufacture a specific HSS size. Atlas Tube offers the broadest size range of HSS in North America, including Jumbo sizes. 

However, a listing in the database or manual does not guarantee that a size is readily available from stock. Even though HSS producers maintain regular production rollings, some profiles, particularly larger or custom ones, may require a minimum production run. To prevent delays and unexpected costs, always contact a producer before finalizing your drawings for bid. A quick consultation can confirm whether your chosen size is a standard, readily available product or if it will require a special order. 

The Bottom Line: HSS is the Standard 

The transition from TS to HSS was a critical step in modernizing the steel construction industry and aligning it with global practices. While the term “Tube Steel” is part of our industry’s history, HSS is the correct, current, and universally understood designation. 

By using the proper terminology and verifying product availability, you can ensure your projects are specified accurately and do not encounter unnecessary sourcing challenges.