SFS Performance Standards: UK Fire, Acoustic & Thermal Guide

All UK SFS performance standards in one place

Specifiers, fire engineers, thermal designers, acousticians and main contractor compliance teams all need to navigate the same regulatory framework when working with SFS. This hub page collects the authoritative reference articles on each performance area, so you can find what you need quickly rather than searching across multiple guides.

If you’re working on a Building Safety Act Higher-Risk Building, all four performance areas matter — and the documentation requirements are unprecedented. If you’re working on a non-HRB project, Parts A, B, E and L still apply via Building Regulations but the evidence burden is significantly lighter.

How SFS meets the Building Safety Act

The Building Safety Act 2022 introduced a Gateway regime for Higher-Risk Buildings (HRBs) — buildings at least 18m tall or with at least 7 storeys, containing at least two residential units. Three Gateways must be passed:

• Gateway 1 (pre-planning): demonstrates the building’s fire safety strategy at concept design stage
• Gateway 2 (pre-construction): demonstrates the technical fire safety design before construction starts
• Gateway 3 (pre-occupation): demonstrates that the building was built as designed and is safe to occupy

For SFS subcontractors, Gateway 2 is the focus. It requires a documented Evidence Pack covering: structural calculations sealed by a chartered engineer, fire performance data with test certification, U-value calculations, acoustic test data, supplier traceability for every component, installation method statements, and a Construction Control Plan signed by the principal contractor.

Reputable SFS subcontractors deliver this as a packaged ‘Gateway 2 Evidence Pack’ — typically 40-80 pages depending on project scope, indexed for ease of inspector review. See our SFS Gateway 2 Evidence Pack overview for what that documentation looks like in practice.

Fire performance: 60, 90 and 120-minute systems

SFS frames are inherently non-combustible (Class A1 to BS EN 13501-1) — the steel itself does not burn and contributes nothing to fire load. Fire performance of SFS wall systems comes from the plasterboard layers fitted to the frame, the insulation between studs, and the integrity of any service penetrations.

Standard achievable fire ratings (REI = load-bearing capacity / integrity / insulation to BS EN 13501-2):

• REI 30: Basic plasterboard each face — rarely specified in modern UK construction except for non-critical internal partitions
• REI 60: Standard for internal partitions and external infill walls in most mid-rise buildings — 1 × 15mm Type F plasterboard each face or 2 × 12.5mm Type F each face
• REI 90: Standard for separating walls between dwellings and for many escape routes — 2 × 15mm Type F plasterboard each face
• REI 120: Required for some HRB applications and for protected escape routes in tall buildings — 2 × 19mm Type F plasterboard each face or specialist fire boards as per the manufacturer’s test certificate

Full detail on each rating, including the specific board manufacturers and test certificate references, is in our SFS fire resistance ratings guide. For drylining-specific fire requirements (a separate but related topic), see our fire-rated drylining specification guide.

Acoustic performance: Part E compliance

Part E of the Building Regulations (Resistance to the Passage of Sound) sets minimum acoustic standards for residential construction:

• Separating walls between dwellings: DnT,w + Ctr ≥ 45 dB (airborne sound, weighted with low-frequency correction)
• Separating floors between dwellings: DnT,w + Ctr ≥ 45 dB plus L’nT,w ≤ 62 dB (impact sound)
• Internal walls between rooms in the same dwelling: Rw ≥ 40 dB

Standard SFS partition walls (single stud, mineral wool infill, double plasterboard each face) achieve Rw 45-50 dB. Twin-stud separating walls (two independent stud frames with an air gap) achieve Rw 55-58 dB, sufficient for Part E compliance with margin.

Performance is verified on completion via Pre-Completion Testing (PCT) — an acoustician tests a sample of party walls and floors, and any non-compliance triggers remedial work or design review. For the detail on acoustic build-ups and PCT preparation, see our acoustic drylining solutions article.

Thermal performance: Part L 2025 and the Future Homes Standard

Part L 2025 (in force since June 2025) sets external wall U-value targets of 0.18 W/m²K for new dwellings. The Future Homes Standard transitions toward 0.15 W/m²K through 2026-2028.

Standard SFS external wall build-ups achieve:

• 22 W/m²K with 100mm stone wool insulation in 100mm studs (older Part L compliant, no longer sufficient for new build)
• 18 W/m²K with 150mm stone wool insulation in 150mm studs (Part L 2025 compliant)
• 15 W/m²K with 200mm stone wool insulation in 200mm studs, thermal break tape, and perforated stud profiles (Future Homes Standard compliant)
• 13 W/m²K with the above plus continuous external insulation (typically 30-50mm rigid mineral wool) carried through cladding battens

Critical: nominal U-value calculations don’t capture thermal bridging through the steel studs themselves. Detailed psi-value calculation at all junctions is mandatory under Part L 2025. For the full thermal performance reference, see our SFS U-values and thermal performance guide.

Drylining performance specifications

Drylining (the internal plasterboard wall finish, with or without an SFS frame) carries its own performance requirements — particularly for fire compliance and acoustic isolation in residential and healthcare applications. Our fire-rated drylining specification guide covers the specifics for drylining alone, and our acoustic drylining solutions article covers the acoustic dimension.

Standards quick-reference table

The UK regulatory framework for SFS construction in 2026, summarised:

• Part A (Structure): Eurocode 3 — BS EN 1993-1-3 for cold-formed steel design. Calculations sealed by a chartered structural engineer.
• Part B (Fire): Approved Document B 2022 (with 2023 amendments) plus BS 476 and BS EN 13501 for component test methods. A2 or better cladding required on HRBs under Regulation 7.
• Part E (Acoustics): Approved Document E. DnT,w + Ctr ≥ 45 dB for separating walls between dwellings. PCT mandatory on completion.
• Part L (Thermal): Approved Document L (Volume 1 for dwellings) 2025 amendments. U-value 0.18 W/m²K for new dwelling external walls, transitioning to 0.15 W/m²K under Future Homes Standard.
• Building Safety Act 2022: Gateway regime for HRBs. Gateway 2 Evidence Pack required pre-construction. Building Safety Regulator (BSR) approval mandatory.
• BSEN 1090: Execution of steel structures. Defines minimum standards for SFS fabrication and installation quality.
• BS 9991 (Fire safety in flats and apartments): Provides design guidance for residential fire strategies, including SFS-specific provisions.

Common compliance failures and how to avoid them

Five recurring compliance failures in SFS construction, in order of frequency we encounter on remediation projects:

• Wrong sheathing for fire spec. Wood-based OSB used in place of cement-bonded board on a fire-rated wall. Saves money in the short term, fails the fire test in the long term. Avoid by tying the spec to a specific named product and requiring delivery tickets matched to wall locations.
• Inadequate acoustic separation in twin-stud walls. A single screw inadvertently fixed across both stud frames creates a sound bridge that wipes out the airborne performance. Avoid by clear method statements, training installers, and inspecting the install before second-side plasterboard is fitted.
• Skipped or punctured vapour control layer. Causes interstitial condensation, mould and slow corrosion of the steel studs. Avoid by inspecting the VCL before any other trade enters the work zone.
• Missed fire-stopping at service penetrations. Every cable, pipe and socket box through a fire-rated wall needs intumescent fire-stop sealing. Common failure point because penetrations happen at different times across multiple trades.
• Documentation gaps for Gateway 2. Components installed without delivery tickets logged, batch numbers recorded, or installation sign-off. Recoverable on the day with diligent paperwork; harder to fix retrospectively. Avoid by setting up the Gateway 2 Evidence Pack template at project mobilisation and capturing data as you go.

Talk to our engineers about your compliance requirements

Whether you’re at concept design wondering how SFS fits your fire strategy, at detailed design needing thermal bridging calculations, or at pre-construction assembling a Gateway 2 Evidence Pack, our engineering team can support. Get in touch for project-specific compliance advice on UK SFS construction.

Frequently asked questions

The most common compliance questions from UK SFS specifiers and fire engineers.

What performance standards apply to SFS construction in the UK?

SFS construction in the UK must meet Building Regulations Parts A (structure), B (fire), E (acoustics), L (thermal) and the Building Safety Act for Higher-Risk Buildings. Plus BS EN Eurocodes for structural design, BS 476 / BS EN 13501 for fire, and Approved Document E for sound insulation between dwellings.

Does SFS need to meet Part L 2025?

Yes. SFS external walls must meet Part L 2025 U-value targets of 0.18 W/m²K for new dwellings (lower for non-residential). The Future Homes Standard introduces tighter targets from 2025-2026 (U=0.15 W/m²K), requiring deeper insulation or higher-performance products in SFS wall build-ups.

What fire rating can SFS achieve?

SFS frames are inherently non-combustible (Class A1). SFS wall systems achieve 60, 90 or 120 minutes of fire resistance depending on plasterboard specification and number of layers. A typical 60-minute spec uses 15mm fire-rated plasterboard each face; 90-min and 120-min specs use multiple layers or specialist boards.

Can SFS meet Part E acoustic requirements?

Yes. SFS partition walls achieve Rw 45-53 dB depending on build-up — sufficient for Part E (Resistance to the Passage of Sound) compliance in apartments and hotels. Double-stud or staggered-stud SFS systems with mineral wool infill reach 58 dB+, exceeding Part E requirements for separating walls between dwellings.

What evidence do I need for Building Safety Act Gateway 2?

Gateway 2 evidence for SFS work includes: structural calculations sealed by a chartered engineer, fire performance data with test certification, U-value calculations, acoustic test data, supplier traceability for all components, installation method statements, and a Construction Control Plan signed by the principal contractor. Reputable SFS subcontractors provide this as a packaged ‘Gateway 2 Evidence Pack’.