Structural Steel Installation in London Renovations: What's Involved
Steel beams are a fundamental element of most London residential extensions, loft conversions, and structural alterations. The installation of a structural steel beam — whether to create a load-bearing opening, support a loft conversion floor, or span an extension — is a precise structural operation that requires proper engineering, temporary propping, and safe working practice.
Why Steel Is Used
In domestic construction, structural steel (typically hot-rolled universal beam or universal column sections) is used where:
- A span is too long for timber to carry efficiently
- A load-bearing wall is being removed and the load must be transferred to padstones and columns
- A loft conversion floor needs to be strengthened significantly (new floor joists bear onto a new steel perimeter)
- An extension requires a long-span ridge beam or new loadpath
The Pre-Installation Process
Structural engineer design: Before any steel is ordered or installed, a structural engineer must design the beam — calculating the loads it must carry, specifying the section size and grade, and designing the bearing details at each end. This design is submitted to Building Control.
Temporary propping: Before the load-bearing wall or structure being altered is disturbed, temporary propping must be in place to transfer the existing structural load safely during the works. Propping is typically acrow props and spreader boards. Rushing ahead without adequate propping is a significant safety risk.
Steel procurement: Structural steel sections are ordered from a steel stockist, cut to length, and often pre-drilled for bolted connections. Lead time is typically 3–7 working days from order to delivery for standard sections.
Installation Process
- Temporary props erected below the structure to be removed or modified
- Opening created to receive the beam (in a wall, or in the roof/ceiling structure)
- Padstones (engineering brick or concrete) laid at bearing points to receive the beam ends
- Beam craned, hoisted, or manually installed into position using appropriate lifting equipment
- Beam checked for level and alignment
- Connections made (bolted or welded depending on design)
- Structural fire protection applied where required (intumescent paint for 30-minute or 60-minute fire resistance)
- Building Control inspection before making good
- Making good — plasterboard, insulation, decoration
Steel Beam Sizes for Common Applications
Common London residential steel beam applications:
| Application | Typical section size |
|---|---|
| Single doorway or window opening (up to 2m span) | 127 × 76 × 13 UB or 152 × 89 × 16 UB |
| Chimney breast removal opening (2–3m span) | 152 × 89 × 16 UB or 203 × 102 × 23 UB |
| Rear wall removal for kitchen extension (4–5m span) | 254 × 102 × 25 UB to 305 × 127 × 37 UB |
| Full rear wall removal with load above (5–6m span) | 356 × 127 × 39 UB to 457 × 152 × 52 UB |
Actual sizes are determined by the structural engineer's calculation and depend on loads, span, and bearing conditions.
Fire Protection
In most domestic applications, structural steel must achieve 30-minute fire resistance to comply with Building Regulations Part B. This is typically achieved by:
- Intumescent paint: Applied in controlled coat thicknesses, expands in fire to insulate the steel
- Board encasement: Fire-rated board systems around the beam
RCB Design & Build
RCB Design & Build installs structural steels as part of extension, loft conversion, and structural alteration projects — coordinating with the structural engineer, Building Control, and the overall programme.