Hollow Structural Sections, commonly referred to as HSS, are a popular choice in structural engineering and fabrication. Their clean geometry, aesthetic appeal, and efficient load distribution make them attractive across a wide range of applications. But like any material, they come with real trade-offs that buyers and engineers need to understand before committing to a project. If you are sourcing steel for maritime, offshore, construction, or industrial work, knowing where HSS falls short can save you time, money, and significant headaches down the line.
What is HSS and where is it commonly used?
HSS refers to steel sections with a hollow cross-section, available in square, rectangular, and circular profiles. The square steel tube is one of the most widely recognised forms, valued for its uniform appearance and structural symmetry. These sections are manufactured by forming flat steel into a tube and welding the seam, or by seamless extrusion for higher-pressure applications.
Common applications include:
- Structural columns and frames in commercial and industrial buildings
- Offshore platforms and support structures
- Ship deck furniture, railings, and internal framing
- Machinery guards, masts, and architectural features
- Bridge and truss components where aesthetics matter
Their torsional stiffness and compact footprint make them especially useful where space is limited or where a clean, finished look is required. That said, the same properties that make HSS attractive in certain situations are precisely what create challenges in others.
What are the main disadvantages of using HSS?
Despite their appeal, hollow structural sections carry a set of disadvantages that can affect fabrication, long-term performance, and overall project cost. Understanding these limitations upfront is essential for anyone involved in procurement or structural specification.
The most significant drawbacks include difficulty in welding and connection design, the risk of internal corrosion that cannot be inspected or treated once sealed, higher material cost compared to equivalent open sections, limited flexibility in making field modifications, and more complex fabrication requirements that demand specialist knowledge and equipment.
These are not reasons to avoid HSS entirely, but they are factors that must be weighed carefully against the structural and aesthetic benefits the material offers.
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Ask your steel question →Why is welding HSS more difficult than open sections?
Welding hollow sections, particularly square steel tube profiles, is considerably more demanding than welding open sections such as I-beams or channels. The closed geometry creates several practical complications that affect both the quality of the joint and the time required to complete it.
When connecting HSS members to each other, fabricators must work around the tube wall without access to the interior. This means all welding must be performed from the outside, which limits the angles and techniques available. Cope holes, which are sometimes used to improve weld access in open sections, are not practical in sealed hollow profiles.
Branch connections, where one tube meets another at an angle, require precise profiling of the tube end to achieve a proper fit. This profiling, often called saddle cutting or cope cutting, demands accurate machinery and skilled operators. Poor fit-up at these joints leads to weld defects, stress concentrations, and potential fatigue failure in dynamic or cyclic loading environments such as offshore structures.
End connections to plates or flanges also require careful design. Because the wall thickness of a square steel tube is concentrated at the perimeter, load transfer into the connection zone must be managed carefully to avoid punching shear or local buckling at the joint.
How does internal corrosion become a problem in HSS?
One of the most serious long-term risks with sealed hollow sections is internal corrosion. Once an HSS member is fabricated and sealed at both ends, the interior cavity is effectively inaccessible. Any moisture that enters during fabrication, transportation, or installation becomes trapped and can initiate corrosion from the inside out.
This is particularly problematic in marine and offshore environments, where humidity and salt-laden air are constant factors. Internal corrosion is invisible during routine inspection, meaning it can progress significantly before any external sign appears. By the time surface blistering or section loss becomes visible, the structural integrity of the member may already be compromised.
To manage this risk, designers and fabricators typically seal all openings completely to prevent moisture ingress, or alternatively provide drainage holes and ventilation to allow moisture to escape. Some specifications call for internal coatings or the injection of desiccant compounds, though these add cost and complexity. In critical applications, the choice between sealing and venting requires careful engineering judgment based on the exposure environment.
When should you choose open sections over HSS?
Open sections such as universal beams, channels, and angles are often the better choice when fabrication flexibility, inspection access, or connection simplicity is a priority. If a project involves complex bolted connections, frequent field modifications, or tight budget constraints, open sections typically offer a more practical and cost-effective solution.
Open sections are also preferable when the structure will be subject to regular inspection for corrosion, fatigue cracking, or mechanical damage. Because all surfaces of an open section are accessible, maintenance teams can inspect, clean, and recoat the steel without restriction.
In applications where torsional loading is not a primary concern and where the visual appearance of the steel is not critical, open sections deliver equivalent structural performance at lower fabrication cost and with simpler connection detailing. For straightforward industrial framing, support structures, and secondary steelwork, they are frequently the smarter choice.
What are the cost implications of using HSS in structural projects?
HSS typically carries a higher material cost per kilogram than equivalent open sections, partly due to the additional manufacturing steps involved in producing the hollow profile and partly due to tighter tolerances and quality requirements. For projects using large quantities of square steel tube or rectangular hollow sections, this premium can add up significantly across the total bill of materials.
Fabrication costs also tend to be higher. The specialist cutting, profiling, and welding required for hollow section connections demands more skilled labour and more time than comparable open section work. If the fabricator does not have the right equipment for saddle cutting or end profiling, additional outsourcing costs may apply.
Surface treatment and coating costs can also differ. Because internal surfaces are inaccessible once sealed, any internal protection must be applied before assembly, adding a step to the production sequence. External galvanizing of sealed hollow sections requires careful management of vent holes to allow zinc to flow through and gases to escape safely during the hot-dip process, which adds a further layer of planning and cost.
How Marine Steel helps with hollow section sourcing and tube processing
Choosing the right steel section for your project is only half the challenge. Getting it cut, processed, and delivered on time is where many buyers run into difficulty. That is where we come in.
At Marine Steel, we supply a wide range of hollow sections including square steel tube profiles, and we back that supply with in-house tube processing capabilities that remove the need to coordinate multiple suppliers:
- Precision cutting to size, drilling, and rolling to your exact specifications
- Bending, sand blasting, priming, and galvanizing services
- Conservation treatments and custom processing to drawing
- Class certification and documentation where required
- Stock held across our warehouses in Rotterdam and Houston for fast turnaround
Whether you need standard stock or a fully processed, ready-to-install solution, we think along with you to find the right answer for your project. You explain what you need once, and we take it from there. Explore our full range of steel products or contact our team directly for a fast quotation.
