What is SFS cladding?
SFS cladding is the complete external wall system that uses a Steel Framing System as the structural substrate, with an outer cladding finish providing the building’s visible weather skin. It’s the dominant external wall method on UK mid-rise commercial construction — used on Build-to-Rent apartments, student accommodation, hotels, hospitals and offices.
An SFS cladding system isn’t a single product. It’s a layered assembly that has to perform structurally (carrying the cladding weight and wind load), thermally (achieving Part L 2025 U-value targets), acoustically (meeting Part E for residential), in fire (60-120 minutes, A2-rated for Higher-Risk Buildings), and aesthetically (matching the architect’s intent for the finished façade). Each layer in the stack has a job. Get any one wrong and the system fails.
This guide covers what goes into an SFS cladding system, how the critical details work, and what specifiers and main contractors need to get right at design and procurement stage.
SFS cladding vs SFS infill — clearing up the confusion
The terms SFS cladding and SFS infill are often used as if they mean the same thing. They don’t quite.
SFS infill strictly refers to the steel framing itself — the non-loadbearing cold-formed steel wall built between the structural floors of a building. It is the skeleton.
SFS cladding strictly refers to the whole external wall assembly — the SFS infill frame plus sheathing, breather membrane, insulation, cavity battens, and the outer cladding finish that the building shows to the world.
In practice, an SFS infill wall becomes an SFS cladding system the moment you add the layers that turn it from a frame into a finished façade. The terminology overlaps because the work is delivered as a single package by the same subcontractor.
When tendering, be explicit: is the package SFS infill only (frame to sheathing), or full SFS cladding (frame to finished outer leaf)? Significant cost and scope difference.
The cladding stack: layer by layer
A standard UK SFS cladding wall is built up in seven layers, working from outside to inside. Different cladding finishes change the outer two layers; the inner five stay broadly the same.
Layer 1 — Outer cladding leaf
The visible cladding finish: brick, render, rainscreen panels, terracotta, metal, or fibre cement. Carries no structural load other than its own weight (transferred via cladding rails or brick ties back to the SFS frame), and provides the building’s appearance, weather protection and rainscreen detail.
Layer 2 — Cavity and battens
A 50mm minimum drained and ventilated cavity sits behind the outer leaf. Vertical battens (timber or aluminium) carry the cladding back to the frame at appropriate centres for the cladding type. Brick has wider centres; rainscreen has tight centres. The cavity allows any moisture that gets past the outer leaf to drain out at the base.
Layer 3 — Breather membrane
A vapour-permeable, water-resistant membrane laps the sheathing board, allowing any vapour from inside the wall to escape outward while preventing rain that gets past the cladding from reaching the structural elements behind. Critical for long-term wall health — a poorly-installed breather membrane is one of the most common SFS failure points.
Layer 4 — Sheathing board
A 12-15mm cement-bonded board (or specialist sheathing for fire-engineered systems) is fixed directly to the outside face of the SFS frame. The sheathing provides racking stability to the steel studs, a continuous fire-resistant layer, and the substrate the breather membrane laps onto.
Layer 5 — SFS frame
The cold-formed light gauge steel studs and tracks themselves — typically 100mm or 150mm deep, at 600mm centres, with mineral wool insulation between studs. This is the structural and thermal core of the wall.
Layer 6 — Vapour control layer (VCL)
On the warm side of the insulation, a vapour control layer prevents warm moist air from inside the building condensing within the wall cavity. Typically a heavy-duty polythene sheet, lapped and taped at all joints. As critical as the breather membrane and equally easy to install badly.
Layer 7 — Internal lining
Plasterboard (single or double-layer, fire-rated as appropriate for the wall’s fire rating) screwed to the internal face of the SFS frame. Forms the finished internal wall surface ready for decoration.
We’ve documented the standard build-ups for each combination of outer leaf, fire rating and thermal performance in our SFS wall build-up specification reference — worth bookmarking if you’re specifying SFS regularly.
Cladding options on SFS
Five main cladding finishes work well over SFS. Each has different cost, weight, fire performance and aesthetic implications.
Brick
Traditional outer leaf brick, supported on stainless steel windposts and brick ties tied back to the SFS frame. Suitable up to 4 storeys with standard ties; up to 8 storeys with engineered support; intermediate masonry support angles at intervals beyond that. Heavy (1.8-2.2 kN/m²), expensive (£120-180/m² for the brick alone), and slow — but the gold standard for aesthetic permanence and longevity in the UK market.
Render
Thin-coat polymer-modified render applied directly to a render carrier board fixed over the SFS frame. Light (0.3-0.5 kN/m²), relatively cheap (£60-90/m²), and fast. Vulnerable to algae and cracking if poorly detailed; needs regular maintenance to look its best after 10-15 years.
Rainscreen
Engineered cladding panels — high-pressure laminate (HPL), aluminium composite (post-Grenfell, A2-rated only), fibre cement, terracotta, ceramic — fixed to a structural carrier system over the SFS frame. The dominant cladding choice on UK mid-rise commercial since 2020. Costs vary widely (£120-380/m²) depending on panel material. Quick to install once the carrier is up; gives architects huge design flexibility.
Terracotta and ceramic
Premium rainscreen subset. Visually distinctive, durable (50+ year life), naturally A2-rated. Expensive (£280-450/m²) but increasingly specified on high-end residential and cultural buildings.
Metal panels
Profiled or flat metal panels — aluminium, copper, zinc, weathering steel — fixed to a carrier rail system. Light, durable, contemporary aesthetic. Cost varies from £180/m² (basic aluminium) to £450/m² (zinc or copper). Best suited to commercial and cultural buildings rather than residential.
Critical detail: head deflection
The single most important detail in an SFS cladding system is the head deflection joint at the top of every wall. Get this wrong and the cladding cracks, the cladding finish blows, and the wall fails its weather test.
Concrete floor slabs deflect downward under live load (people, furniture, dynamic loads). The deflection is small (typically 5-20mm) but it happens repeatedly throughout the building’s life. If the SFS wall is rigidly fixed to the underside of the slab above, that deflection transfers into the wall — and the wall has nowhere to go. The cladding cracks.
The solution: a deflection head joint that allows the slab above to move independently of the wall below. Typically achieved with a slip joint at the top track of the SFS frame — the track is fixed to the slab above with a 20-25mm vertical gap (the ‘deflection allowance’) filled with a flexible material like compressible foam or fire-rated mineral wool. The studs slide within the track as the slab deflects.
Head deflection allowance is calculated by the structural engineer for each specific floor. Typical UK figures: 15-25mm. The detail must be maintained continuously across the wall — broken in just one location and the deflection concentrates at that point, magnifying the failure.
We’ve covered this in detail in our SFS deflection heads guide — required reading for anyone detailing SFS for the first time.
Critical detail: brick ties and windposts
Where the cladding is brick, the connection back to the SFS frame is handled by stainless steel brick ties (small wire ties at typically 300-450mm vertical and 600mm horizontal centres) and windposts (vertical steel sections that span between floors and carry wind loads on the brick back to the SFS frame at the floor levels).
The structural engineer specifies tie spacing and windpost sizing based on wind loads, brick weight and floor-to-floor height. Above 4 storeys, brick cladding usually requires intermediate masonry support angles fixed to the SFS frame at each floor level to relieve the brick of its own weight — without these, the brick at the base of a tall wall fails under cumulative dead load.
Fire compliance: A2 cladding for the Building Safety Act
Since the Grenfell Tower fire and the subsequent legislative response (the Building Safety Act 2022, Approved Document B revisions, Regulation 7), all external cladding on Higher-Risk Buildings (HRBs — 18m+ or 7+ storeys with residential use) must use A2 or better-rated materials. Combustible cladding is prohibited on HRBs and heavily restricted on other multi-residential buildings.
An SFS cladding system can be fully A2-rated. The frame is inherently non-combustible (A1). The insulation between studs must be A2 or A1 (typically stone wool — never PIR or PUR on HRBs). The sheathing must be cement-bonded (A1) rather than wood-based. The outer cladding must be A2 or A1 (rules out HPL and ACM-PE, includes terracotta, fibre cement, A2-rated aluminium composite, brick, and most natural stone).
Documenting this compliance is the SFS subcontractor’s job at Gateway 2. Every component must be traceable to a test certificate and supplier batch. See our SFS Gateway 2 Evidence Pack overview for what that documentation looks like in practice.
Cost ranges by cladding type
These are typical UK 2026 ranges for a complete SFS cladding system (frame plus all layers plus outer finish, supplied and installed). Add 10-25% for fire-engineered specifications on Higher-Risk Buildings; subtract 5-10% on simpler low-rise applications.
- SFS infill frame only (no outer leaf): £85-120/m²
- SFS with render outer leaf: £160-220/m²
- SFS with brick outer leaf: £250-380/m²
- SFS with rainscreen (mid-range, e.g. fibre cement): £230-310/m²
- SFS with rainscreen (premium, e.g. terracotta or zinc): £350-550/m²
These are realistic ranges for tier-1 main contractor procurement in 2026. For granular pricing on your project specification, our SFS cost guide covers the per-square-metre breakdown by component.
Installation sequence
A typical SFS cladding installation follows this 8-step sequence on a per-elevation basis:
- Survey and mark out — confirm slab edges, set out window openings and key dimensions
- Install SFS frame studs and tracks, including deflection head detail and windposts where required
- Install internal mineral wool insulation between studs
- Apply vapour control layer to the internal face, lapped and taped
- Fix internal lining (plasterboard) and complete electrical first-fix in service zones
- Apply cement-bonded sheathing board to external face of frame
- Apply breather membrane to external face of sheathing, lapped and taped
- Install cavity battens, then the outer cladding finish (brick, render carrier, or rainscreen carrier)
Steps 1-5 take place internally; steps 6-8 require external scaffold or mast-climbing access. On a well-managed project, the SFS subcontractor will phase the work so internal trades can start in completed zones while external cladding continues on others.
Common cladding failures and how to avoid them
Three failure modes account for the majority of SFS cladding problems we see on retrofit and remediation work:
- Failed vapour control layer. Skipped, torn, badly lapped, or punctured during follow-on trades. Result: interstitial condensation, mould, and slow corrosion of the steel studs. Avoid by inspecting and signing off the VCL before any other trade enters the work zone.
- Inadequate deflection head allowance. Detailed at design but installed wrong on-site, with the slip joint blocked by an over-enthusiastic plasterer or insulation installer. Result: cladding cracks within 12-18 months. Avoid by clear method statements, training installers, and inspecting deflection joints at the close-out stage.
- Wrong sheathing for the 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 single named product on the supplier list and requiring delivery tickets matched to wall locations.
Get a cladding spec for your project
Every SFS cladding system is project-specific. Wind load, height, fire rating, acoustic requirement, aesthetic intent and budget all drive the right specification. If you’re working on a UK mid-rise project and want a tailored SFS cladding specification — or a competitive quote against an existing one — contact the BAS Frames team. We’ll respond within 24 hours with a structured response covering scope, cost range and indicative programme.
Frequently asked questions
The most common questions from architects, specifiers and main contractors specifying SFS cladding for the first time.
What is SFS cladding?
SFS cladding refers to using a Steel Framing System as the substrate for an external cladding system. The SFS frame is built between the building’s primary structural floors, sheathed and weatherproofed, then clad with brick, render, rainscreen, terracotta or metal panels to form the finished façade.
What’s the difference between SFS cladding and SFS infill?
The terms overlap. SFS infill describes the frame itself (the steel structure built between floors). SFS cladding describes the full wall assembly including the outer cladding finish. An SFS infill wall becomes an SFS cladding system once you add the sheathing, breather, cavity and outer leaf.
What head deflection allowance do SFS cladding systems need?
Typical head deflection allowance for SFS cladding is 15-25mm to accommodate slab deflection under live load. The exact figure comes from the structural engineer’s calculation for that specific floor. Deflection head detail uses a slip joint at the top track to allow vertical movement without compromising the cladding.
Can SFS cladding be A2-rated for the Building Safety Act?
Yes. SFS frames are inherently non-combustible (cold-formed steel is A1-rated). The full cladding system achieves A2 or better when specified with non-combustible sheathing (e.g. cement-bonded board), A2 insulation (typically stone wool), and an A2-rated outer leaf. This is mandatory for Higher-Risk Buildings.
How much does SFS cladding cost per square metre in the UK?
SFS cladding cost depends on the outer finish. Typical UK 2026 ranges: SFS infill frame alone £85-£120/m², full build-up with rainscreen £180-£280/m², full build-up with brick outer leaf £250-£400/m², full build-up with high-spec rainscreen (terracotta, metal) £350-£550/m². Add £15-£40/m² for fire-rated specifications.
