What Is Secondary Steelwork? Primary vs Secondary Steel Explained

On most building projects, the steel is split into two parts: the primary steelwork that holds the building up, and the secondary steelwork that everything else hangs off. Secondary steel is easy to overlook, and it's often where programme problems start.

Primary vs secondary steelwork

Primary steelwork is the main structural frame: the columns, main beams, rafters and bracing that carry the building's loads down to the foundations.

Secondary steelwork is the steel that's supported by the primary frame or by the building, and supports something else: the cladding, roof, finishes, services or access. It still carries loads, and it still has to be designed and certified, but it isn't part of the main load path.

Typical secondary steelwork

• Purlins and side rails that carry roof and wall cladding.
• Lintels, trimmers and opening steel around doors, windows and service openings.
• Wind posts that support masonry and cladding between floors.
• Canopy frames and entrance canopies.
• Plant supports and platforms for air handling units, chillers, tanks and pipework.
• Mezzanine and access steel, including mezzanine floors, walkways and cat ladders.
• Stairs, balustrades and handrails. See steel staircases and handrails and guardrails.
• Support steel for shopfronts, signage and glazing. See steel shopfronts.

Some contractors call this "miscellaneous metalwork" or "misc steel", especially when it covers stairs, ladders and handrails.

Why secondary steel causes problems

Primary steel is usually designed early and ordered in one package. Secondary steel often depends on information that arrives later: the cladding system, the M&E plant, the glazing and the fit-out. That leads to:

• Late design, because sizes and positions aren't fixed until other trades confirm their details.
• Interface issues, where steel doesn't line up with cladding brackets, plant feet or glazing frames.
• Fixings into finished work, if it's left until after other trades have finished.

The fix is to agree early who designs it, get the other trades' information in on time, and choose a fabricator who can turn small packages round quickly.

Who designs it?

On many projects the structural engineer designs the primary frame and shows secondary steel only in outline. The detailed design is then often a contractor's design portion, done by the fabricator or their engineer. Make sure the contract says who's responsible, because a support steel detail with no owner is a common source of delay.

Standards and certification

Secondary steel is structural steel, so the same rules apply as for the frame. It should be fabricated by a firm certified to BS EN 1090-1, at the execution class the designer specifies, with the documentation to match. Our structural steel regulations guide and EN1090 guide explain more.

Frequently asked questions

Is a steel lintel secondary steelwork? Usually, yes. It supports the wall over an opening rather than forming part of the main frame. In a house, a beam carrying a floor or a wall above is often the main structure for that part of the building.

Can the same contractor do primary and secondary steel? Yes, and it often makes the interfaces simpler. Some projects split them to suit the programme.

Do you take on secondary steel packages? Yes. We fabricate and install secondary and miscellaneous steelwork for main contractors, from plant supports to stairs and handrails, certified to BS EN 1090-1 Execution Level 3. See steel fabrication for main contractors, or send us your drawings.