Light steel framed walls and floors

6.10

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

Topic	Description
Description of system	Key features
Application	Usage, e.g. maximum number of storeys and type of cladding
Durability	Confirmation that minimum design life is 60 years 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 Structural integrity Positions and sizes of holes through members
Claddings	Acceptable claddings Provision of cavity Type of wall ties
Behaviour in relation to fire	Necessary internal linings Fire stops and cavity barriers
Condensation risk	Type, thickness and location of insulation material
Sound insulation	Confirmation that the specification complies with building regulations/Robust Details
Balconies, terraces and parapets	Specific design considerations
Other	Other 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.