Light steel framed walls and floors

6.10.3Certification

Design of the superstructure shall be checked by an NHBC steel frame certifier.

Homes with load-bearing light steel framed walls or floors require two-stage certification confirming that both the system and the project have been checked. The project-specific design check should be undertaken by an NHBC approved steel frame certifier.

Stage 1 – system certification

NHBC requires manufacturers of steel frame systems, which form load-bearing walls or floor panels, 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 and Technical.

The manual should contain the information described in Table 1 (though SCI may ask for additional information).

Table 1: Items considered in the system manual

TopicDescription
Description of systemKey features
ApplicationUsage, e.g. maximum number of storeys and type of cladding
DurabilityConfirmation that minimum design life is 60 years
Grade of steel
Corrosion protection
Supplementary protection
Strength and stabilityStructural 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
Structural integrity
Positions and sizes of holes through members
CladdingsAcceptable claddings
Provision of cavity
Type of wall ties
Behaviour in relation to fireNecessary internal linings
Fire stops and cavity barriers
Condensation riskType, thickness and location of insulation material
Sound insulationConfirmation that the specification complies with building regulations/Robust Details
Balconies, terraces and parapetsSpecific design considerations
OtherOther information of relevance to the designer and steel frame certifier

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

NHBC requires the builder to appoint a steel frame certifier to check the design for the home and the site. The steel frame certifier should:

  • check supporting details and calculations
  • ensure that the proposals are in accordance with the manufacturer’s system certificate (issued by SCI) and this chapter
  • provide confirmation that the requirements have been satisfied for each project
  • issue a ‘project certificate’ to the builder.

The certificate should be available on site for inspection by NHBC.

Project certificates can only be issued by steel frame certifiers who have been approved by NHBC. Applications to become a steel frame certifier should be made to NHBC.