All-in-One Fire & Acoustic Solutions for Boundary and External Walls
KOROK® External Wall Systems are non-loadbearing, fire- and acoustically-rated vertical wall systems combining a zinc-coated steel outer shell with a 400kg/m³ aerated concrete core. BRANZ appraised and designed for New Zealand conditions, they provide durable, high-performance external and boundary wall solutions for commercial and industrial buildings.
Delivering fire rating, acoustic separation, and weather-tight performance in a single integrated assembly, the lightweight system enables faster installation, reduces structural demand, and can eliminate the need for specially engineered slabs on many projects. Available in single-skin or over-clad configurations, the systems are engineered to perform under defined design wind pressures.
How the System Works
The system uses 78mm interlocking panels with a 250mm effective cover width, installed vertically to form a continuous fire- and acoustically-rated barrier. The interlocking geometry limits acoustic leakage while maintaining fire-resisting continuity. The steel shell provides durability and weather protection, and the concrete core delivers inherent fire resistance and acoustic mass. Five system configurations are available:
EX1 – 78mm COLORSTEEL® panel, single-skin system
EX2 – 78mm COLORSTEEL® panel with internal fire-rated lining
EX3 – 78mm panel with engineered over-clad metal system
EX4 / EX5 – Over-clad systems incorporating internal fire-rated lining
All systems provide two-way fire resistance and are designed as vertical in-fill wall systems fixed to supporting primary structures.
External Wall System Engineered for Commercial and Industrial Applications
KOROK® External Wall Systems are suitable for warehouses, factories, sheds, cinemas, lift shafts, and other commercial applications where fire separation and acoustic control are critical.
EX1 and EX2 systems are appraised as single-skin, non-loadbearing, fire- and acoustically-rated external walls. EX3, EX4 and EX5 systems incorporate drained and vented cavity cladding systems and are subject to project-specific engineering design. The systems are designed for defined wind pressures and vertical span limits, ensuring controlled structural behaviour under service and ultimate limit state conditions.
Code Compliance Highlights
Clause B1 – Structure: Designed for self-weight, wind, earthquake, impact, creep and shrinkage in accordance with AS/NZS 1170.
Clause B2 – Durability: Designed to achieve 15-year and 5-year durability performance requirements, subject to environmental exposure category.
Clause C3 – Fire Affecting Areas Beyond the Fire Source: Provides passive fire separation to limit fire spread.
Clause C6 – Structural Stability: Requires supporting primary elements to achieve equivalent fire resistance where applicable.
Clause E2 – External Moisture: Designed to meet external moisture performance requirements.
Clause F2 – Hazardous Building Materials: Does not present a health hazard in service.
Key Performance Ratings
Fire Resistance Rating (2-Way): Up to –/240/240 minutes, depending on system configuration.
Choose from a full range of COLORSTEEL® options to match your project’s external design. Explore our CAD Library for DWG files related to KOROK® External Wall Systems. Access detailed KOROK® External Systems Literature for specifications, installation guides, and more. If you have any questions or need further assistance, contact us for more information.
Durability and Service Life
Service life performance depends on environmental exposure category. COLORSTEEL® MAXAM™ external shells provide up to 25 years resistance to perforation in defined NZS 3604 zones, with paint finish durability of 15 years under normal conditions. Panels are intended to remain rain-washed and fully exposed. Geothermal environments require consultation with the relevant Building Consent Authority.
The internal side lined with 1 layer 19mm GIB Fyreline® or acceptable GIB® alternatives or 2 layers 10mm GIB Fyreline® or acceptable GIB® alternatives.
Longrun profiled steel cladding system as selected.
The internal side lined with 1 layer 19mm GIB Fyreline® or acceptable GIB® alternatives or 2 layers 10mm GIB Fyreline® or acceptable GIB® alternatives. Longrun profiled steel cladding system as selected
1 layer 10mm GIB® Standard plasterboard or equivalent each side
Acoustic insulation must be either Autex GreenStuf SW90 or Pink Batts R 2.2 each side.
KOROK® metal fire flashing is installed to the top C-track.
KOROK® metal KIT flashing is installed to horizontal joints.
90mm steel or timber frame each side
86mm overall. Framing not to touch KOROK® panel or fire flashing
KOROK® metal fire flashing is installed to the top C-track. KOROK® metal KIT flashing is installed to horizontal joints.
1 layer 10mm GIB® Standard plasterboard or equivalent each side
Acoustic insulation must be either Autex GreenStuf SW90 or Pink Batts R 2.2 each side.
KOROK® metal fire flashing is installed to the top C-track.
KOROK® metal KIT flashing is installed to horizontal joints.
90mm steel or timber frame each side
80mm overall. Framing not to touch KOROK® panel or fire flashing
KOROK® metal fire flashing is installed to the top C-track. KOROK® metal KIT flashing is installed to horizontal joints.
KOROK® metal fire flashing is installed to the top C-track OR 13 mm GIB Fyreline® or equivalent x 120 mm strip with sealant is fixed at 250 mm centres top and bottom, using 6g x 32 mm drywall screws.
