Steel profiles classified by cross-sectional shape

The shape of a steel profile is not merely a matter of its name or appearance. The geometry of its cross-section affects the stiffness of the component, its behaviour under load and its suitability for a particular part of a structure. A profile should therefore be selected with regard to its intended use, dimensions, wall thickness and fixing method.

The basic classification distinguishes between open and hollow sections. Open sections include angles, C-sections, Z-sections, T-sections and SIGMA profiles. Hollow sections have circular, square or rectangular cross-sections.

Open sections – Z, C and SIGMA profiles

At e-PROJECT21, we focus primarily on Z, C and SIGMA steel profiles. They are widely used in lightweight steel structures, including as roof purlins and wall girts. They can also serve as load-bearing components in platforms and mezzanines built inside industrial buildings.

C-sections have a cross-section resembling the letter C. Their flat surfaces make it easier to create connections and attach other structural components. They are used as girts, purlins, beams, posts and frame components.

Z-sections are commonly used as roof purlins and wall girts. Their shape allows individual sections to be joined effectively, which is particularly useful when creating longer continuous runs within a structure.

SIGMA profiles have a more complex cross-section with additional stiffening ribs. They are used both in building structures and in solutions designed for specialised infrastructure applications.

A standard profile is not always sufficient

Standard catalogue profiles are suitable for many structures, but they do not meet every requirement. Some projects require different profile dimensions, a different wall thickness or a combination of both modifications.

In such cases, e-PROJECT21 helps verify whether a non-standard Z, C or SIGMA profile can be manufactured. For an initial assessment, a dimensioned drawing is usually sufficient – even a clear hand-drawn sketch – together with information about the required quantity.

An individual approach is particularly important when a customer cannot find a suitable solution in a standard product range or needs assistance in specifying the order requirements. The final selection of components used in a load-bearing structure must always be based on the design documentation and structural calculations.

Hollow sections

Hollow sections include steel tubes and sections with square or rectangular cross-sections. A closed cross-section provides good stiffness in different directions and greater resistance to torsion than many open sections.

Steel tubes are used in applications such as balustrades, installations and supporting structures. Square and rectangular hollow sections are used in frames, columns, fencing, industrial buildings and equipment components. Their flat surfaces make connections easier, while their regular shape contributes to the clean appearance of the finished structure.

Which steel profile should you choose?

The shape of the cross-section alone is not enough to select the correct profile. Its dimensions, wall thickness, length, support conditions, and the type and direction of the applied loads must also be considered. Structural components should therefore be specified in a design or selected by a suitably qualified structural engineer.

If a standard profile does not meet the project requirements, it is worth checking whether a version tailored to the specific application can be manufactured. e-PROJECT21 helps customers define their requirements and verify the production options for profiles with non-standard dimensions or wall thicknesses.