Rectangular steel tubing is one of those materials that goes by several names depending on who you ask and where in the world you are. A procurement professional sourcing steel for a maritime refit might call it RHS, while a structural engineer in the US refers to the same product as HSS. Understanding the terminology helps you order the right material, communicate clearly with suppliers, and avoid costly specification errors. This article breaks down the naming conventions, standard sizes, steel grades, and real-world applications of rectangular hollow sections.
What is the difference between RHS, HSS, and structural tubing?
Rectangular steel tubing is most commonly known as RHS, which stands for Rectangular Hollow Section. This is the standard term used in Europe, Australia, and most international markets. In North America, the same product is typically called HSS, or Hollow Structural Section. You may also encounter the terms structural tubing or box section, which are informal names used in fabrication and construction environments.
The underlying product is the same: a hollow steel profile with a rectangular cross-section, manufactured with consistent wall thickness on all four sides. The difference is purely regional and terminological, not technical. When ordering from an international supplier, it is worth confirming which naming convention they use to make sure you are comparing the right product.
It is also worth distinguishing rectangular tubing from square steel tube, which follows the same manufacturing process but has equal width and height dimensions. Both fall under the broader category of hollow structural sections and are often stocked alongside each other. Square and rectangular hollow sections share the same steel grades, surface finishes, and fabrication methods, so many of the specifications discussed in this article apply to both.
What are the standard sizes of rectangular steel tubing?
Rectangular hollow sections are produced in a wide range of sizes to suit different load requirements and design constraints. Standard dimensions are defined by outer width, outer height, and wall thickness. Common widths and heights range from as small as 40 x 20 mm up to 400 x 200 mm and beyond, with wall thicknesses typically ranging from 2 mm to 16 mm depending on the section size.
In practice, the most frequently used sizes in maritime, offshore, and industrial applications fall within the following ranges:
- Small sections (e.g. 50 x 30 mm, 60 x 40 mm) used for brackets, supports, and secondary structures
- Medium sections (e.g. 100 x 50 mm, 120 x 80 mm) used for frames, handrails, and equipment bases
- Large sections (e.g. 200 x 100 mm, 300 x 150 mm) used in primary structural applications and heavy fabrications
Standard lengths are typically 6 or 12 metres, though cutting to size is common practice when working with custom fabrications. If you need a specific length or profile combination that is not available off the shelf, a supplier with in-house cutting and processing capabilities can prepare material to your exact requirements.
What steel grades are used for rectangular hollow sections?
The steel grade of a rectangular hollow section determines its strength, weldability, and suitability for specific environments. Several grades are widely used across different industries.
In Europe, S235 and S355 are the most common structural grades, where the number indicates the minimum yield strength in megapascals. S355 is the higher-strength option and is preferred in offshore and heavy industrial applications where structural integrity under load is critical.
In the United States and for projects governed by American standards, rectangular hollow sections are often specified to ASTM A500, which covers cold-formed welded and seamless carbon steel structural tubing. Grade B and Grade C are the most commonly used variants within this standard. For higher-strength requirements, ASTM A513 is another option for mechanical tubing applications.
For corrosive environments, including marine and offshore applications, stainless steel hollow sections are available in grades such as 304 and 316. Grade 316 offers superior resistance to chloride-induced corrosion, making it the preferred choice for exposed deck structures, coastal installations, and equipment that comes into regular contact with seawater.
Selecting the right grade matters. Using a structural grade that is too low for the application can lead to deformation or failure under load. Using an unnecessarily high-grade material adds cost without benefit. When in doubt, a supplier with genuine product knowledge can help you match the grade to the application.
Where is rectangular steel tubing used in maritime and industrial applications?
Rectangular hollow sections are among the most versatile structural materials in use today. Their combination of high strength-to-weight ratio, clean geometry, and ease of fabrication makes them suitable for a broad range of applications.
In the maritime sector, RHS is used in ship superstructures, deck frames, hatch coamings, gangways, and equipment supports. The rectangular profile allows for efficient load distribution and straightforward welded connections, which is important in environments where structural reliability is non-negotiable.
In offshore and energy applications, rectangular tubing appears in platform structures, module frames, pipe racks, and cable trays. The ability to specify wall thickness and steel grade precisely makes it well suited to environments where both mechanical loads and environmental conditions are demanding.
In construction and industrial fabrication, RHS and square steel tube are used for columns, beams, machine frames, conveyor structures, and architectural steelwork. Their predictable dimensions and consistent surface quality make them easy to work with in both manual and automated fabrication processes.
- Structural framing in vessels, platforms, and industrial buildings
- Equipment bases and supports where dimensional precision is required
- Handrails, ladders, and access structures in maritime and offshore environments
The full range of steel products at Marine Steel includes hollow sections suitable for all of these applications, with material available in both standard and custom dimensions.
How Marine Steel helps you source rectangular hollow sections
We stock a broad range of rectangular hollow sections and square steel tube across our warehouses in Rotterdam and Houston. Whether you need standard structural grades for a construction project or marine-grade stainless steel for an offshore application, we can supply the right material with the right documentation.
Here is what we offer:
- Rectangular and square hollow sections in S235, S355, ASTM A500, and stainless steel grades
- Custom cutting to length and precision fabrication to your drawings or specifications
- Material certificates and documentation for projects requiring traceability
- Fast quotation and delivery from stock, with no need to source from multiple suppliers
- Technical advice on grade selection, wall thickness, and surface treatment
With over 15 years of experience serving maritime, offshore, and industrial clients, we understand that getting the specification right the first time matters. You tell us what you need once, and we take it from there. Contact us to request a quote or get advice on the right hollow section for your project.
