Light steel framing

6.10.3Structural certification

The LSF system shall be adequately tested and certified. The design of superstructures with primary structural components formed from LSF shall be checked by an NHBC registered LSF certifier.

Primary structural components formed from LSF require two-stage certification confirming that both the system and the project have been checked. External infill does not require Stage 1 and 2 certification (see Clause 6.10.5).

Stage 1 – system certification

NHBC requires manufacturers of LSF systems, which form primary structural components, to submit a system manual to the Steel Construction Institute (SCI) for assessment. The manufacturer is the company which assembles the steel frame sections to form the wall and/or floor panels. If in doubt, consult NHBC Standards, Innovation and Research.

The manual should contain the information described in Table 1. Further performance issues may be considered at the discretion of SCI and the manufacturer (see Table 7).

Table 1: Items included in the system manual

Description of system■ Key features
Application■ Usage, e.g. maximum number of storeys and type of cladding
Durability■ Demonstrate that design life is at least 60 years (including environment category)
■ Grade of steel
■ Corrosion protection
■ Supplementary protection
Strength and stability■ Structural design philosophy (including codes of practice referenced and test reports)
■ Grade of steel (traceability)
■ Section properties
■ Loading
■ Ultimate limit state
■ Serviceability limit state
■ Resistance to overturning
■ Racking resistance
■ Holding down
■ Connections within the system
■ Connections with other building elements
■ Structural integrity
■ Positions and sizes of holes through members
Additional checks where LSF is used in volumetric construction■ Module-to-module connections (strength as well as accuracy)
■ Module-to-foundation connections
■ Rigidity in transportation
■ Lifting

Where there are choices (e.g. types of claddings), the manufacturer will need to specify which options the SCI is to consider in its assessment. Upon satisfactory completion, SCI will approve the manufacturer’s system manual and issue a numbered ‘system certificate’ which includes:

  • a detailed description of the system
  • details of usage limitations
  • information for reference by the designer and steel frame project certifier.

Stage 2 – project certification

The design of all primary structural components should be subject to a Stage 2 certification check by an NHBC registered LSF certifier.

The LSF certifier should:

  • „be listed on NHBC’s list of LSF certifiers
  • „be a suitably qualified and experienced civil or structural engineer with appropriate professional indemnity insurance
  • „not be the designer of the LSF or be employed by the same practice
  • „check supporting details and calculations
  • „ensure the Stage 1 system certificate is valid and current
  • ensure that the proposals are in accordance with the manufacturer’s Stage 1 system certificate (issued by SCI) and this chapter
  • „provide confirmation that the requirements have been satisfied for the project
  • provide the registered builder with the completed and signed project certificate confirming assessment of structural adequacy for each specific project.

The registered builder should ensure that the completed Stage 2 certificate is available on site for inspection by NHBC.

Contact NHBC Standards, Innovation and Research:

  • „if you require contact details of frame certifiers, or
  • „to apply to become an LSF certifier.