From fire protection to airtightness, thermal performance to structural integrity – every component in a through-wall build-up plays a vital role. Yet, with such a wide range of materials and regulations to consider, understanding how these layers interact is essential for specifiers, contractors, and installers alike.
At Klasse, we don’t just manufacture individual products – we help you build complete, compliant, high-performance wall systems. Here’s our guide to the key layers in a typical external through-wall build-up, and where Klasse solutions fit in.
1. Steel Framing System (SFS) – The Structural Backbone
The SFS provides the structural skeleton for non-load-bearing external walls in modern buildings. It defines wall depth, spacing, and overall support.
While Klasse doesn’t supply the SFS itself, our products are designed to integrate seamlessly with leading steel framing systems used across the UK.
2. External Sheathing Board – Strength, Stability, and Safety
Fixed to the SFS, the sheathing board provides additional characteristics such as racking strength, a durable fixing surface, and early-stage weather protection. Critically, it also contributes to passive fire protection.
- Klasse G-board: A lightweight, exposure-resistant (12-month guarantee), A1-rated gypsum board that is 30% lighter than traditional cement boards and boasts a market leading pull-through strength.
- Klasse C-board: A calcium silicate cement, high-density sheathing board that has exceptional impact resistance, 12 months weather exposure guarantee, has a high racking strength and is also A1 rated.
These boards are BBA certified and tested for use in demanding wall build-ups.
3. Airtightness & Moisture Control Layer – Sealing the Envelope
To protect the wall system from air leakage and water ingress, joints and penetrations must be effectively sealed.
- Klasse Airtight Tape: Engineered for long-term adhesion and resistance to weathering. Applied over board joints to maintain airtightness and improve energy efficiency.
- KlasseWRAP: Our range of Air and Vapour Control Layers (AVCLs) is designed to regulate moisture and airflow within the building fabric. KlasseWRAP enhances airtightness, reduces condensation risk, and supports overall thermal performance.
- KlasseWRAP Breather Membrane: A high-performance, water-resistant yet vapour-permeable membrane. Installed externally, it prevents wind-driven rain and water ingress while allowing trapped moisture to escape, helping the wall system stay dry and breathe effectively.
- KlasseSEAL Façade Sealing Membrane: A flexible and durable membrane designed for perimeter and façade sealing. KlasseSEAL forms a robust barrier against water penetration at critical junctions while accommodating movement, essential for protecting façade integrity in modern rainscreen and cladding systems.
Correct application of these components helps prevent condensation within the wall cavity, safeguarding insulation and internal components for long-term building performance. Klasse G-board is unique in that it can eliminate the need for a breather membrane, helping to lessen project costs.
4. Rainscreen Insulation – Fire-Resistant Thermal Performance
External insulation provides the thermal barrier, keeping buildings warm in winter and cool in summer. It must resist moisture and meet strict fire standards, especially in high-rise or high-occupancy buildings.
- KlasseROCK: A Euroclass A1-rated stone wool insulation board, designed specifically for rainscreen systems. It offers excellent fire resistance, thermal performance, and acoustic dampening.
Installed over the sheathing board, KlasseROCK supports a breathable yet insulated cavity system.
5. Cavity Barriers and Support Systems – Safety and Spacing
Within the ventilated cavity, horizontal and vertical fire barriers are installed to prevent fire and smoke from spreading behind the cladding. Support rails or brackets fix the cladding back to the structure.
Klasse products are compatible with typical barrier systems and allow installers to maintain clear, unbroken layers across interfaces.
6. Rainscreen Cladding – The Aesthetic Shield
Finally, the outermost layer is the cladding – the visible face of the building. It provides weather protection, UV resistance, and visual impact. While Klasse does not supply cladding, our build-up ensures a safe, solid substrate to support a wide range of finishes – from metal to terracotta, brick slips to fibre cement.
Why Every Layer Matters
It’s not enough for each component to perform well in isolation – a successful through-wall build-up depends on how well each layer works with the next. That’s why Klasse designs its products for compatibility, compliance, and simplicity on site, we help ensure:
- Regulatory compliance (including EN13501-1 fire performance)
- 3rd party certification for peace of mind
- System integration with SFS and cladding suppliers
- Time-saving installation backed by technical project support
Need Help with Your Specification?
Klasse works closely with specifiers, main contractors, and SFS installers to develop tailored wall build-ups. Whether you need fire test data, installation details, or design guidance, our technical team is ready to help with unrivalled project support. Just contact us today to get started.
