A steel erector installs structural steelwork to the designs provided by a structural engineer. On domestic projects this typically means installing RSJ (Rolled Steel Joist) or universal beams to support walls above openings such as knocked-through rooms or chimney breast removals. On larger commercial or agricultural projects a steel erector may erect complete structural steel frames, portal frames and mezzanine floors. The work involves propping, lifting, bolting and welding steel members to engineered connection details, and ensuring the finished structure is plumb, level and correctly fire-protected. Building Control inspection is required at the structural stage.
What they do
- RSJ and universal beam installation for wall openings
- Steel column installation and base plate fixing
- Portal frame erection for garages and workshops
- Steel staircase installation
- Mezzanine floor installation
- Balcony steel frame installation
- Structural connection bolting and welding
- Intumescent fire protection application
When you need one
A steel erector is required whenever structural steelwork must be installed. Always have the structural engineer's design and calculations ready before appointing.
Typical costs (UK, 2025)
| Job type | Typical cost |
|---|---|
| RSJ beam supply and installation (domestic) | £1,000 - £3,000 |
| Load-bearing wall removal steelwork (supply and fit) | £1,500 - £5,000 |
| Portal frame erection (labour only) | £3,000 - £10,000+ |
| Steel staircase (supply and install) | £3,000 - £8,000 |
| Structural engineer design and calculations | £500 - £1,500 |
| Intumescent fire protection (per element) | £100 - £400 |
Steel beam costs depend heavily on beam size, span, access constraints and propping requirements. Always obtain the structural engineer's specification before getting quotes - different steel sizes give very different costs.
Qualifications to look for
BCSA members are fabricators and erectors who have been assessed against technical and quality standards. For commercial or larger structural steel projects, using a BCSA member provides assurance of quality and correct practice.
The CSCS card confirms health and safety competence. Steel erectors on site are expected to hold an appropriate CSCS card. The CISRS Construction Skills card is relevant for erectors with scaffolding duties.
How to find a reputable steel erector
Frequently asked questions
Do I need a structural engineer for steel beam installation?
Yes - all structural steelwork must be designed by a structural engineer who will specify the beam size, connection details and padstone requirements. The engineer's design is required for Building Control approval. The steel erector follows the engineer's drawings; they do not design the structure themselves.
How are RSJ beams installed in a house?
RSJ (Rolled Steel Joist) or universal beam installation involves temporary propping of the existing structure, cutting the opening, installing steel padstones or concrete bearing pads, lifting the beam into position (using a scaffold hoist, acro jack or crane depending on size and access), and making the connections. The steel is then fire-protected with intumescent paint or board. Building Control will inspect the installation.
What is a portal frame and when is it used?
A portal frame is a rigid structural steel frame consisting of columns and rafters connected with moment-resisting joints. Portal frames are commonly used for garages, workshops, industrial buildings and agricultural structures. They are typically fabricated off-site and erected on site using a crane. The BCSA (British Constructional Steelwork Association) provides guidance on portal frame design.