The question comes up regularly when engineers are working from a Eurocode-based design and sourcing structural hollow sections: EN 10219 or EN 10210? Both are European standards for structural hollow sections in the same grades, same designation system, same general appearance on a mill certificate. But they’re not interchangeable, and substituting one for the other without reviewing the implications is the kind of shortcut that creates problems later — sometimes at the connection detail, sometimes at the inspection stage, sometimes both.
The difference starts at the manufacturing route and runs through to how the sections behave structurally and how they’re treated in the design code.
The Manufacturing Route
EN 10210 covers hot-finished structural hollow sections. The production process involves forming the tube (typically from seamless billet or from welded strip) and then finishing the section at a temperature above the recrystallization temperature of the steel — roughly 900 degrees Celsius and above. This hot finishing step is a normalizing treatment. It relieves the residual stresses introduced by the forming process and produces a microstructure that’s substantially uniform around the cross-section perimeter.
EN 10219 covers cold-formed welded structural hollow sections. The tube is formed at ambient temperature from flat strip, and the forming process permanently deforms the material into a tube without a subsequent thermal treatment that would normalize the structure. Cold forming introduces residual stresses — compressive residual stresses in the flat faces, tensile residual stresses at the corners — and work-hardens the steel, particularly at the corners where the plastic strain is highest.
The practical result is that EN 10219 structural hollow sections have corners that are harder and stronger in yield than the flat faces, with reduced ductility at the corners relative to the parent flat strip material. The material properties you see on the mill certificate — yield strength, tensile strength, elongation — are measured from a specimen taken from the flat face, not from the corner. The corner material has higher yield strength (due to work hardening) but lower elongation.
What This Means for Structural Design
Eurocode 3 (EN 1993-1-1) treats cold-formed and hot-finished hollow sections differently in two main areas: the buckling curves for compression members, and the corner properties for certain limit state calculations.
For compression members designed to Eurocode 3, the imperfection factor used in the column buckling calculation depends on the buckling curve assigned to the cross-section type. Hot-finished hollow sections (EN 10210) are assigned buckling curve a, which has a lower imperfection factor and therefore gives a higher calculated buckling resistance for the same slenderness ratio. Cold-formed hollow sections (EN 10219) are assigned buckling curve c — a more conservative curve — because the residual stress pattern from cold forming is less favorable for buckling resistance than the normalized condition of hot-finished sections.
For a column at moderate slenderness, the difference between buckling curves a and c can be significant — the hot-finished section can carry more load per unit of steel for the same cross-section dimensions. If a design was developed using EN 10210 sections and someone substitutes EN 10219 sections of the same designation without reviewing the buckling calculation, the column may be undersized for its design load.
The Corner Issue in Practice
EN 10219 Part 2 specifies corner radius tolerances and acknowledges that the corner region of a cold-formed section has different properties than the flat face. The standard permits a reduced effective wall thickness at the corners for certain calculations — specifically for local buckling and for the effective section properties used in thin-wall section classification.
For most standard structural hollow sections in S355 — the most commonly used grade — the sections are compact enough that corner properties don’t govern the buckling behavior of the section itself. The issue becomes more relevant for higher-strength grades (S420, S460) and for thinner-walled sections where the flat face width-to-thickness ratio is larger and local buckling becomes a governing limit state.
For connections — particularly welded connections at the corners of square or rectangular sections — the reduced corner wall thickness in cold-formed sections affects the throat thickness calculation for fillet welds placed at the corner. The radius at the corner means the effective weld length and position differ from what a flat face weld on a hot-finished section provides. EN 1993-1-8 provides the rules, but the connection detail needs to be checked against the actual corner geometry of the cold-formed section, not assumed from a hot-finished section geometry.
When EN 10219 Is the Right Choice
Cold-formed sections are not a second-best option — they’re the economically appropriate choice for most standard building frame applications where the members are stocky enough that buckling curve differences are minor, and where the load levels don’t push the design to its limits.
Cold-forming is more economical than hot-finishing for standard sizes: the production process is faster, the energy cost is lower, and the range of sizes and wall thicknesses available from stock is broader. For standard S275 and S355 sections in the common size range — 40×40 through 200×200 square, and equivalent rectangular and circular sections — cold-formed EN 10219 sections are what the market stocks. Hot-finished EN 10210 sections in the same sizes exist but often require mill ordering with corresponding lead times and price premiums.
The structural engineer’s job is to know which standard was assumed in the design calculation and to specify it consistently so that the supplied material matches those assumptions. “Structural hollow sections to EN 10219 or EN 10210” is not a complete specification when the buckling design used the hot-finished curve — it’s an invitation to receive whichever is cheaper and in stock, which may or may not satisfy the design basis.
The Procurement Conversation
For most commercial building projects, EN 10219 is what the market provides and what most Eurocode designs can accommodate. For heavily loaded columns, slender sections, or applications where the higher ductility of the normalized condition matters — seismic design, connections with high rotational demand, fatigue-critical structures — the hot-finished EN 10210 sections may be the appropriate specification.
Either way, state which standard applies in the purchase order. Don’t let the supplier choose.
