FAQ: Frequently Asked Questions – Metframe Offsite

Metframe is a pre-panelised loadbearing light gauge steel framing system (LGSF) manufactured offsite in a controlled factory environment before being delivered to site for rapid assembly. Panels are manufactured to precise tolerances and designed to form the structural frame for low to medium rise construction.

Offsite LGSF construction transfers a significant proportion of the structural frame manufacture from site to a controlled factory environment. For systems such as Metframe, structural panels are designed, detailed and manufactured offsite before being delivered to site for assembly.

Compared with traditional onsite construction, this typically provides:

• Improved dimensional accuracy and repeatability through factory-controlled production.
• Reduced site labour and fewer wet trades.
• Reduced structure weight of superstructure and saving in foundation size
• Reduced construction programmes, savings on interest payments and a faster return on investment.
• Better programme certainty, subject to early design freeze, coordination and logistics planning.
• Reduced site waste and improved material efficiency.
• Less disruption on constrained sites, with fewer deliveries and shorter structural frame durations.

Metframe is particularly well suited to building types with repetitive layouts, regular grids and repeated wall panel arrangements, where the benefits of offsite manufacture, standardisation and rapid site assembly can be fully realised. Typical applications include:

• Student accommodation
• Residential developments
• Hotels
• Care homes/Later Living developments

The suitability of each solution depends on project-specific structural, fire, acoustic and thermal requirements.

Metframe uses heavy gauge studs to form load bearing structures for low to medium rise construction up to 15 storeys high. Metframe structures can incorporate either steel joisted or concrete floors as required.

Panelised offsite construction can reduce programme durations compared with traditional building methods by manufacturing structural elements in parallel with site preparation works. Factory production also delivers greater dimensional accuracy, reduced site labour requirements and a faster route to a watertight envelope.

Metframe combines factory manufactured LGSF, in-house structural engineering expertise, BIM-driven design, UKAS-accredited fire testing, approved installation partners and the backing of voestalpine, one of the world’s leading steel and engineering groups.

Yes. The system is particularly suited to restricted urban environments because panel sizes, deliveries and installation sequences can be coordinated before work starts on site, reducing congestion and improving programme management.

Yes. Metframe is considered a Modern Method of Construction (MMC) although it has been used in the UK construction industry for over 25 years.

Factory-manufactured steel framing is produced to engineered tolerances using automated manufacturing processes. This enables a high degree of dimensional accuracy, which can help improve installation efficiency and reduce site adjustments

Pre-panelised systems offer:

• Faster erection times
• Reduced site labour
• Improved health and safety
• Better dimensional control
• Reduced waste
• Improved programme certainty
• Earlier start of follow on trades
• Earlier weather-tight envelopes
• Greater quality consistency

These benefits are achieved by manufacturing key structural components in a controlled factory environment before delivery to site

Developers increasingly require solutions that reduce programme risk, improve quality consistency and support increasingly demanding building safety requirements. Factory-manufactured steel framing systems can help achieve these objectives through controlled production, predictable installation programmes and detailed engineering documentation

Metframe is designed on a project-specific basis using recognised UK and European design standards, together with the requirements of the Building Regulations.

For structural design, light gauge steel framing is generally designed in accordance with Eurocode 3, particularly BS EN 1993-1-3 for cold-formed steel members and sheeting, with reference to BS EN 1993-1-1 for general steel design rules and BS EN 1993-1-8 for connection design. Actions are derived from the BS EN 1991 series, including imposed, wind and snow loads as applicable, with load combinations taken from BS EN 1990 and the relevant UK National Annexes. Structural robustness is considered in accordance with BS EN 1991-1-7.

The wider building performance requirements are coordinated with the relevant parts of the Building Regulations, including Part A for structure, Part B for fire safety, Part E for resistance to sound and Part L for conservation of fuel and power. Steel Construction Institute (SCI) guidance in P402 – Light Gauge Steel Framing in Residential Construction, also highlights that design must address serviceability, durability, thermal performance, acoustic performance, fire resistance and interface detailing, rather than treating the frame as an isolated set of structural members.

Metframe sections are primarily manufactured from pre-hot dipped galvanised steel with a minimum yield strength of 450N/mm².

Metframe sections are manufactured from pre-hot dipped galvanised steel with Z275 coating. Z275 coating means 275 grams of zinc per square metre summed over both faces of the steel strip, this corresponds to approximately 0.02mm overall thickness of zinc per face. A reduced range of sections are also available with a thicker Z600 coating.

Yes. Metframe includes engineered solutions for balconies, lift shafts, stairwells, roof systems, walkways, podium construction interfaces and integrated structural steel design

The National Light-Gauge Steelwork Specification (NLSS) sets out tolerances for both manufactured light gauge steel components and the erected frame. These tolerances should be considered collectively, as deviations from material supply, manufacture and installation can be additive. The NLSS requires the overall accumulated deviation to remain within the permitted deviations for the completed structure.

For the foundation interface, the NLSS identifies key pre-installation tolerances including foundation edge position of +15 mm / -0 mm, foundation level of -6 mm / +0 mm, and vertical wall support position of +/-25 mm. Holding down bolts or bolt groups require tighter control, with typical positional tolerances of +/-10 mm where adjustment is provided, or +/-3 mm where adjustment is not provided.

During installation, the prepared foundations and holding down bolts should be inspected for position and level before the light gauge steel frame is installed. Any discrepancies outside the specified tolerances should be reported and remedial works agreed before installation proceeds. Base tracks may be levelled using galvanised steel shims, but plastic packs should not be used. Where the gap beneath a base track is between 10 mm and 20 mm, the NLSS requires grouting under the full length of the base track. Where the gap exceeds 20 mm, the Light-gauge Steelwork Manufacturer and Designer should advise on the required action.

For the erected frame, the NLSS gives typical permitted deviations including +/-5 mm for wall base track position, 5 mm for storey height, 5 mm for eccentricity at wall panel splices, and 5 mm for relative joist level. The practical implication is that LGSF requires accurate setting out and a coordinated foundation interface, but it also includes defined adjustment, packing and grouting provisions to deal with normal construction tolerances.

Metsec works with a network of Metframe Licensed Installers who are familiar with the specific requirements of the system, including panel handling, temporary stability, fixing requirements, tolerances, sequencing and interface coordination. This helps ensure that the frame is installed in accordance with the project design information and the intended construction sequence.

Using experienced licensed installers supports installation consistency, reduces the risk of avoidable site issues and helps maintain programme certainty. Metsec can also provide project-specific design information, drawings and technical support to assist coordination between the installer, main contractor and wider design team. The precise scope of installation responsibility, supervision and site support should be agreed at project procurement stage.

Factory manufactured panels, coordinated delivery sequences and rapid installation methods enable significantly faster construction programmes than many traditional building approaches. Stair cores, lift shafts and follow-on trades can also progress efficiently as the structure rises.

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When used in a “warm frame” environment, Metframe sections achieve a design life in excess of 60 years. For further guidance for steel with different exposure conditions, consult the Steel Construction Institute publication ED022 – Durability of Light Steel Construction

The galvanised zinc coating protects the steel in two ways. First, it acts as a physical barrier, limiting contact between the steel, moisture and oxygen. Secondly, zinc is sacrificial to steel, so at small scratches, cut edges or fixing penetrations the surrounding zinc corrodes preferentially, helping to protect the exposed steel. Durability remains dependent on the coating thickness, exposure conditions and effective control of moisture ingress or condensation.

Damaged areas of corrosion protection must be reinstated with an appropriate zinc-rich paint. Local areas with exposed edges of steel (ie. cut ends, bolt holes, tek screw penetrations) are protected by sacrificial loss of the zinc coating and require no further attention.

All voestalpine Metsec sections are manufactured with a hot dip galvanised coating to ensure the durability of the frame for internal applications not directly exposed to moisture. Control of moisture ingress and condensation is essential and should be accounted for in design and construction.

Steel is classified as Euroclass A1 and is therefore non-combustible. However, the relevant consideration is the fire resistance of the complete SFS wall assembly, assessed using tests such as BS EN 1364-1, rather than the reaction-to-fire classification of individual components under BS EN 13501-1.

The Building Safety Act places greater emphasis on competence, traceability and accountable evidence. Metframe supports these requirements through detailed design information, structural calculations, fire performance evidence, BIM modelling, controlled manufacturing processes and documented project records

For more information on the use of LGSF please consult Metsec Technical Guidance Note MET-TGD-04 Metframe & Higher Risk Buildings.

Duty holders are increasingly expected to demonstrate not only product performance but also how performance claims can be verified.

Traceability enables stakeholders to understand:

• What system was specified.
• Which components were used.
• What evidence supports performance claims.
• Whether substitutions have occurred.
• What maintenance or future modifications may affect performance.

Traceable information supports compliance, accountability and effective building management.

The Building Safety Act increases the importance of traceability, competence and accountable information. Offsite systems can support these requirements through documented design processes, controlled manufacturing procedures, BIM models, engineering calculations and traceable performance evidence. Metframe combines these advantages with extensive UKAS-accredited fire testing and recognised assessments

Metsec holds a wide range of recognised accreditations including:          

• NHBC/SCI system certification
• UKCA marking
• CE marking
• BIM accreditation
• ISO 9001
• ISO 14001
• ISO 45001
• ISO 50001
• BES 6001 responsible sourcing

Metsec has invested heavily in UKAS-accredited fire testing and can offer fire performance solutions from 60-120 minutes.

Metframe fire performance claims are supported by a comprehensive UKAS-accredited fire testing such as loadbearing wall testing to BS EN 1365-1. All performance claims are tested as complete assemblies, including the Metframe sections, boarding, insulation and fixings, with realistic applied loading. Where wall constructions are non-symmetrical, fire testing has been undertaken from both directions to demonstrate performance for the relevant exposure conditions and to avoid relying on assumptions about the more onerous fire side.

Metsec also contributed to the development of industry publications such as SCI P424 – Fire Resistance of Light Steel Framing, and experimental testing such as on two-sided fire exposure discussed in SCI P442 – Design of Load Bearing Light Steel Walls Exposed to Fire on Two Sides.

Not all evidence carries the same weight. When assessing the suitability of an offsite system, consideration should be given to the quality, applicability and traceability of the evidence supporting a performance claim.

A typical hierarchy of evidence may include:

• UKAS-accredited fire testing
• Third-party assessments
• Engineering judgement
• Manufacturer declarations

The closer the evidence is to the proposed installation, the greater confidence can generally be placed in the claim. A clear hierarchy of evidence also supports Building Safety Act obligations and helps maintain the Golden Thread of information throughout the lifecycle of a building.

Yes. Metsec’s fire testing programme includes solutions incorporating multiple insulation, sheathing and plasterboard manufacturers, giving designers greater flexibility while maintaining access to tested performance data.

The Code for Construction Product Information (CCPI) was developed to improve the quality and transparency of construction product information.

CCPI focuses on ensuring information is:

• Clear
• Accurate
• Accessible
• Up to date
• Unambiguous

For specifiers and duty holders, this provides greater confidence that published information can be relied upon throughout the design and construction process.

Metsec’s Metframe System has achieved CCPI verification, demonstrating a commitment to transparent and evidence-based product information.

Scottish projects often require a Building Warrant process supported by certification from a Structural Engineer Registration (SER) approved engineer. Metsec provides specific design information and supporting documentation to assist project teams with the SER submission process.

Metsec can provide structural calculations, wind loading calculations, stability assessments, disproportionate collapse information, connection details, fire performance information, design philosophy documentation, general arrangement drawings and supporting technical information required within the SER process.

Yes. Metframe sections are UKCA marked in accordance with BS EN 1090, where applicable to the structural components being supplied.

Metsec operates a certified Factory Production Control process for the manufacture of structural cold-formed steel components. This supports UKCA marking and provides traceability of material, manufacturing control and compliance with the relevant execution requirements.

The Declaration of Performance for Purlins and Framing sections is available from the Metsec downloads area.  

100% of the steel sections can be recycled at the end of use or life.

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Quality, Health, Safety and the Environment are considered to be of utmost importance and voestalpine Metsec shall actively promote and administer a strong Quality, Health, Safety, Environmental and Ethical culture amongst staff, visitors and sub-contractors.

To assure these objectives are realised, voestalpine Metsec plc have established an Integrated Management System in accordance with PAS 99: 2012, which incorporates the requirements of BS EN ISO 9001 for Quality Management, BS EN ISO 14001 for Environmental Management, and ISO 45001 for Health & Safety Management.

Metsec Decarb incorporates steel produced using manufacturing processes designed to significantly reduce embodied carbon compared with conventional alternatives. Decarb solutions are available across Metsec product ranges, helping support project sustainability targets without compromising performance.

Yes. LGSF systems can support embodied carbon reduction strategies through efficient structural design, optimisation of material use and the availability of lower embodied carbon steel alternatives such as Metsec Decarb.

Steel Construction Institute (SCI) publications SCI P447: Embodied Carbon of Light Steel Framing with Composite Floors, and SCI P446: Embodied Carbon of Light Steel Framing with Joisted Floors summarise studies on comparable six-storey residential buildings. These studies show that light steel framing can deliver a lower embodied carbon structure than a reinforced concrete frame with light steel infill walls. For the joisted floor option, the light steel structure achieved 125 kgCO2e/m² GFA, 38% lower than the reinforced concrete comparison and corresponding to a SCORS A rating. For the composite floor option, the light steel structure achieved 158 kgCO2e/m² GFA, 22% lower than the reinforced concrete comparison and corresponding to a SCORS B rating.

These reductions are achieved primarily through efficient structural form, low self-weight and material optimisation. The SCI work also reports Module D credits associated with future recycling potential, namely -30 kgCO2e/m² for the joisted floor scheme and -40 kgCO2e/m² for the composite floor scheme. Metsec Decarb steel may provide a further opportunity to reduce embodied carbon, subject to project-specific specification, EPD data and the adopted whole-life carbon assessment scope.

Yes. Metsec provides Environmental Product Declarations for its purlins and framing products, including a third-party verified EPD for standard steel purlins and framing, and a separate EPD for Metsec Decarb purlins and framing. These declarations provide independently verified environmental impact data in accordance with recognised EPD standards and can be used to support embodied carbon assessments, specification decisions and project sustainability submissions.

The current Metsec EPD’s is available from the Metsec downloads area. Project teams should always use the latest published EPD applicable to the specified product range.

voestalpine Metsec can offer product warranty for our components, collateral design warranty for our engineering services and our MetWALL Perform performance warranty for our specified systems.

MetWALL Perform is the industry leading 30-year performance warranty covering fire, thermal, acoustic and structural performance. Our Warranty is based on the wide-ranging performance testing and assessment, and sits in addition to our collateral design warranty; Metsec’s own product warranty and PI insurance.

Yes. voestalpine Metsec carries professional indemnity insurance for its design-related activities. A copy of our £5m professional indemnity insurance certificate is available from the Metsec download area. Project teams should refer to the current published certificate for policy details, scope of cover and any applicable limitations.

Design responsibility carries risk. Professional indemnity insurance can provide assurance that design services are supported by appropriate cover should issues arise relating to professional design activities.

Metframe designs are supported by professional indemnity insurance and collateral warranty options, providing additional confidence for clients and project teams.

Buildings are constructed from systems, not individual products.

A single component may perform perfectly whilst the overall wall assembly fails to meet expectations if interfaces, compatibility or installation requirements have not been fully considered.

System warranties and tested wall solutions provide greater confidence that the complete assembly has been considered rather than individual products being assessed in isolation.

The performance of a building may need to be supported for decades after construction.

When selecting a supplier, designers and developers may wish to consider:

• Long-term business stability
• Professional indemnity cover
• Warranty support
• Technical resource
• Product continuity
• Ongoing compliance support

A financially stable organisation is often better positioned to continue supporting projects, warranties and technical enquiries throughout the life of the building.

Metsec forms part of voestalpine, an international steel and technology group, providing customers with confidence in long-term support and technical capability.

Steel framing is not an off-the-shelf product. Every project presents different requirements relating to:

• Wind loading
• Building geometry
• Structural frame movements
• Façade loads
• Fire strategy
• Buildability

Manufacturers with dedicated in-house design teams can provide a coordinated solution that considers both product capability and project-specific requirements.

Metsec’s design team includes chartered structural engineers and specialist Metframe designers, enabling design, detailing and technical support to be delivered from a single source.