If you work in construction, offshore, or maritime procurement, you have almost certainly come across the terms RHS, SHS, and CHS. These three abbreviations all refer to hollow section steel — structural tubes used across a huge range of applications. But they are not interchangeable, and choosing the wrong profile can affect the strength, aesthetics, and cost of your entire project. This guide breaks down exactly what each type is, how they differ, and how to choose the right one for the job.
What are RHS, SHS, and CHS hollow sections?
Hollow sections are structural steel tubes manufactured with a hollow cross-section. They are widely used in construction, fabrication, offshore structures, shipbuilding, and industrial frameworks. The three main types are:
- RHS (Rectangular Hollow Section): A tube with a rectangular cross-section — two longer sides and two shorter sides. The most versatile profile for structural framing and support.
- SHS (Square Hollow Section): A tube with equal sides on all four faces. Technically a subtype of RHS, but treated as its own category because of its distinct symmetrical properties.
- CHS (Circular Hollow Section): A round tube with a circular cross-section. Commonly used where torsional strength, fluid flow, or aesthetics are a priority.
All three profiles are produced by cold forming or hot finishing, and they are available in a wide range of wall thicknesses and dimensions. You can find them in structural carbon steel, stainless steel, and other grades depending on the application.
What is the difference between RHS, SHS, and CHS?
The core difference lies in their cross-sectional shape, and that shape directly determines how each profile behaves under load.
RHS has different strength values along its two axes. The wider face resists bending in one direction better than the other, which makes it ideal for beams, lintels, and horizontal support members where the load direction is predictable.
SHS is symmetrical on all sides, meaning it performs equally in all directions. This makes it a popular choice for columns, posts, and frames where loads may come from multiple directions. Its clean, square appearance also works well for visible architectural structures.
CHS has no corners, which gives it superior torsional resistance and an even stress distribution around its entire perimeter. It is the preferred choice for applications involving twisting forces, high-pressure systems, or situations where wind loading from any direction must be handled efficiently.
Which hollow section is strongest for structural use?
This question does not have a single answer because strength depends on the type of load you are dealing with.
For axial compression (loads pushing straight down), CHS is generally the most efficient profile. Its circular shape distributes compressive stress evenly, making it excellent for columns and support legs on offshore platforms and industrial structures.
For bending in one direction, RHS outperforms the others when oriented correctly. The deeper face of a rectangular section provides a higher section modulus, meaning it resists bending more effectively per kilogram of steel used.
For equal loading in all directions, SHS is a reliable and predictable choice. Its symmetry means you do not need to worry about orientation during installation.
In practice, the right answer always depends on your specific load case, span, and safety requirements. When in doubt, consult a structural engineer or a supplier who can advise on specifications.
When should you use RHS instead of SHS or CHS?
Use RHS when:
- You are building a beam or horizontal support where the load acts primarily in one direction
- You need a flat surface on the top or bottom for connections, brackets, or welding
- You are working with limited vertical space and need a profile that is wider than it is tall, or vice versa
- Your design calls for a rectangular opening or frame shape
SHS is a better fit when you need a column or post with equal performance in all horizontal directions, or when the clean visual appearance of a square profile matters. CHS is the go-to choice for round handrails, pipe racks, offshore jacket structures, and any application involving internal fluid flow or high torsional stress.
What materials and grades are hollow sections available in?
Hollow sections are produced in several material grades depending on the intended use. The most common options include:
- S235 and S355: Standard structural carbon steel grades used in construction and general fabrication. S355 offers higher yield strength and is preferred for demanding structural applications.
- Stainless steel (e.g. 304, 316): Used where corrosion resistance is essential, such as in marine environments, offshore structures, and food processing facilities. Grade 316 offers superior resistance to chlorides and saltwater.
- ASTM grades: Common in projects with US or international specifications. ASTM A500 is a widely used standard for cold-formed hollow sections in structural applications.
Wall thickness is another critical variable. Thicker walls increase load capacity but also add weight and cost. Always match the wall thickness to your structural calculations rather than defaulting to the heaviest available option.
If you are sourcing for a maritime or offshore project, material certification is often a requirement. Certified documentation confirms that the material meets the specified grade and traceability standards — something worth confirming with your supplier before ordering.
How do you choose the right hollow section for your project?
Start with your load case. Ask yourself: In which direction will the load act, and is it a bending load, a compressive load, or a torsional load? That single question will point you toward RHS, SHS, or CHS respectively in most cases.
Next, consider the connection method. Square and rectangular sections are easier to weld flat connections onto. Circular sections require profiling or saddle cuts for branch connections, which adds fabrication time.
Also factor in the environment. A coastal or offshore structure needs a corrosion-resistant grade. A covered indoor frame in a dry warehouse can use standard carbon steel without issue.
Finally, check availability. Not every dimension and grade is stocked everywhere. Working with a supplier who carries a broad range of steel products in stock means you avoid delays caused by special orders or long lead times.
How Marine Steel helps you select and source the right hollow section
Choosing between RHS, SHS, and CHS is straightforward once you understand the principles — but sourcing the right profile in the right grade, dimension, and certification can be a different challenge entirely. That is where we come in.
- We stock a broad range of hollow sections in structural carbon steel and stainless steel grades
- Our team thinks along with you on specifications — you do not need to arrive with all the answers
- We offer tube processing services including cutting to size, bending, drilling, and custom fabrication
- Material certificates and class documentation are available where required
- With warehouses in Rotterdam and Houston, we serve maritime, offshore, construction, and industrial clients worldwide
Whether you need a standard profile off the shelf or a custom-processed section built to your drawing, we provide a complete solution from a single source. Get in touch with our team and tell us what you need — we will take it from there.
