The New Zealand Building Code has specific fire rating requirements for external cladding systems to prevent the spread of fire vertically and horizontally across building exteriors. These requirements vary based on factors such as building height, proximity to property boundaries, and the risk group of the building.
Here are the key requirements:
- Vertical Fire Spread:
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- External wall cladding on multi-story buildings must prevent fire from spreading more than 3.5 meters vertically from the fire source. This is particularly important for buildings over 10 meters in height.
- Materials and Ignitability:
- For buildings located within 1 meter of a property boundary, the cladding materials must either be non-combustible or must not ignite when exposed to radiant flux of 50 kW/m² for 15, depending on the building’s importance level. Importance levels are based on factors such as building use and occupancy, with more stringent requirements for buildings like schools and hospitals (Importance Levels 3 and 4).
- Testing and Compliance:
- Compliance can be demonstrated through testing in accordance with standards like ISO 5660 or AS/NZS 3837 for smaller buildings (below 25 meters), while large-scale testing (e.g., BS 8414) may be required for taller structures (over 25 meters).
- Weathering and Maintenance:
- In certain situations, exterior cladding systems may be subject to accelerated weathering tests (e.g., ASTM D 2898) to ensure they maintain their fire resistance over time, particularly for external timber cladding treated with intumescent coatings.
These requirements aim to ensure that cladding materials not only resist ignition but also prevent the spread of flames to neighboring properties or upper levels of the same building​.
Non-Combustible Exterior Cladding Requirements
| Building Category | Building Height | Distance to Boundary (< 1.0 m) | Distance to Boundary (≥ 1.0 m) |
|---|---|---|---|
| Commercial Properties | 0 – 10 m | Type A | No Requirement |
| > 10 m | Type A | Type A | |
| SI Risk Group | 0 – 10 m | Type A | Type B |
| > 10 m | Type A | Type A | |
| Residential | 0 – 10 m | Type A | No Requirement |
| > 10 m | Type A | Type B |
- Commercial Properties: Clause C/AS2 – Clause 5.8.
- Residential: Clause C/AS1 – Clause 5.3 (Updated as of 2/11/23).
FireZone Solutions
The FireZone range provides two distinct solutions for achieving a Type A non-combustible fire rating for timber cladding, suitable for buildings up to 25 meters in height. These solutions are tailored for different aesthetic finishes and protection needs, ensuring versatility across various project types.
1. FireZone Vanguard FP – Natural or Stained Finish
FireZone Vanguard FP represents the latest advancement in timber fire-rating technology. This fully impregnating fire-retardant system is an all-natural, non-toxic solution that penetrates deep into the timber’s cellular structure. The system works by saturating the timber with fire-retardant substances that remain dormant until exposed to the high heat of a fire.
When subjected to intense temperatures, the fire retardant in Vanguard FP crystallizes and expands within the timber, blocking its pores and preventing oxygen from feeding the flames. This reaction drastically reduces the timber’s flammability, allowing it to resist ignition and slow the spread of fire. The natural or stained finish maintains the aesthetic integrity of the timber while providing long-lasting fire protection without altering the wood’s appearance.
2. FireZone F1E – Pigmented Finish
FireZone F1E is a high-performance exterior-grade intumescent coating designed specifically for timber cladding. Unlike traditional intumescent systems, FireZone F1E is self-priming and engineered to bond tightly with the timber, ensuring that the coating flexes with the wood as it expands and contracts throughout its life cycle. This flexibility enhances the durability of the coating and reduces the risk of cracking or detachment over time.
When exposed to heat, FireZone F1E forms a thick, protective char layer. The unique fibre interlocking design within the coating ensures that the active intumescent components remain firmly in place, even in extreme conditions such as high winds during bushfires or wildfires. This prevents the coating from becoming dislodged or damaged, maintaining the fire protection throughout the event. The pigmented finish provides a protective and visually appealing layer, offering both fire safety and design versatility for projects.
These solutions, FireZone Vanguard FP and FireZone F1E, offer architects and builders flexibility in terms of finishes while ensuring compliance with stringent fire safety requirements. Whether your project requires a natural timber appearance or a pigmented exterior finish, FireZone has you covered with durable, high-performing fire-rated systems.