If you are sourcing hollow section steel for a maritime, offshore, or construction project, one of the first practical questions you will face is: what wall thickness do I need? It sounds simple, but the answer depends on your application, the loads involved, and the standards your project must meet. This guide walks you through everything you need to know about hollow section wall thicknesses, from standard size ranges to how to choose the right option for your specific situation.
What is hollow section steel and what is it used for?
Hollow section steel is structural steel formed into a closed, hollow profile. The three main shapes are square hollow sections (SHS), rectangular hollow sections (RHS), and circular hollow sections (CHS). Each profile combines structural strength with a relatively low weight, which makes hollow sections a practical choice across a wide range of industries.
In the maritime and offshore world, hollow sections are used in ship structures, deck frameworks, crane booms, and offshore platforms. In construction, they appear in columns, trusses, and support frames. Industrial applications include machine frames, conveyors, and pipework support structures. The closed profile gives hollow sections excellent resistance to both bending and torsion, which is why engineers reach for them when a structure needs to handle loads from multiple directions.
What wall thicknesses does hollow section steel come in?
Wall thickness in hollow sections is measured in millimetres and varies depending on the profile type, the outer dimensions, and the standard being applied. For square and rectangular hollow sections, common wall thicknesses run from 1.5 mm up to 16 mm or more for standard production sizes. Circular hollow sections follow a similar pattern, with thicknesses typically ranging from 1.5 mm to 20 mm depending on the outer diameter.
The most frequently stocked sizes in practical B2B supply tend to fall in these ranges:
- Light wall: 1.5 mm to 3 mm, common in smaller profiles used for secondary structures, furniture frames, and light fabrication
- Medium wall: 3 mm to 8 mm, the most widely used range for general structural applications in construction and industry
- Heavy wall: 8 mm to 20 mm and beyond, used in load-bearing columns, offshore structures, and heavy engineering
For our full range of steel products, including hollow sections in various wall thicknesses and grades, you can browse our product overview. Keep in mind that non-standard thicknesses are often available on request, particularly for larger projects where custom dimensions are required.
What’s the difference between light, medium, and heavy wall hollow sections?
The wall thickness category affects more than just weight. It has a direct impact on the structural performance, weldability, and cost of the section.
Light wall sections are easier to cut, bend, and weld. They are ideal for non-load-bearing or lightly loaded applications. However, they offer less resistance to buckling and are not suitable where significant compressive or bending forces are present.
Medium wall sections strike the balance that most structural engineers work with. They are stiff enough to handle real loads, manageable in terms of fabrication, and available from most steel suppliers in a wide range of outer dimensions. This is the go-to range for columns, beams, and frames in both construction and maritime applications.
Heavy wall sections are specified when strength and rigidity are paramount. Offshore platforms, crane structures, and large column bases often require heavy wall hollow sections. These sections also tend to require more specialised welding procedures and may need preheating depending on the steel grade.
How do you choose the right wall thickness for your application?
Choosing the correct wall thickness is a structural decision, not just a material one. Here is a practical approach to working through it:
- Define the load requirements. What forces will the section carry? Compressive loads, bending moments, and torsional forces all influence how much wall thickness you need. A structural engineer should confirm this for critical applications.
- Check the outer dimensions first. Wall thickness is always specified in relation to the outer profile size. A 100 x 100 mm SHS with a 5 mm wall behaves very differently from the same outer size with a 10 mm wall.
- Consider the connection method. Welded connections to thicker plates or flanges may require a minimum wall thickness to ensure proper weld penetration and joint strength.
- Factor in the environment. Marine and offshore environments introduce corrosion as a variable. A slightly thicker wall can provide a useful corrosion allowance over the service life of the structure.
- Match to available stock. Not every wall thickness is available off the shelf. Working with a supplier who holds broad stock reduces lead time significantly, which matters when a vessel is waiting in port.
If you are unsure about which specification fits your project, it is always worth speaking to a supplier who understands the technical side. Getting the wall thickness wrong can mean costly rework or, in critical applications, a risk of structural failure.
Does wall thickness affect the steel grade or certification required?
Wall thickness and steel grade are related but separate considerations. The grade determines the material properties, such as yield strength and impact resistance, while the wall thickness determines how much material is present to carry the load. That said, there are situations where the two interact.
For example, thicker sections in certain grades may require impact testing at lower temperatures to confirm toughness, particularly for offshore or cold-environment use. Standards such as EN 10210 (hot-finished hollow sections) and EN 10219 (cold-formed hollow sections) specify the mechanical properties and tolerances for each grade and size combination. When certifications and material documentation are required, as is common in maritime and offshore procurement, the wall thickness will appear on the material test certificate alongside the grade, heat number, and mechanical test results.
If your project requires specific certifications or class approval, make sure your supplier can provide the documentation before ordering. Missing paperwork can hold up an entire job, particularly when dealing with classification societies or regulated offshore installations.
How Marine Steel helps you source the right hollow section
Finding the right hollow section steel, with the correct wall thickness, grade, and certification, does not have to be complicated. We stock a broad range of hollow sections and can advise on the right specification for your application, whether you are fitting out a vessel, building an offshore structure, or working on an industrial project.
- Wide stock of hollow sections in multiple wall thicknesses, grades, and profiles
- Custom cutting and processing available to your exact dimensions
- Material certificates and documentation provided as standard
- Locations in Rotterdam and Houston for fast delivery to maritime and industrial hubs
- Technical advice from a team that understands your industry and your time pressure
You explain what you need once, and we handle the rest. Get in touch with our team to discuss your hollow section requirements and receive a fast, accurate quotation.
