NCC Requirements for Facade and Cladding Design

Introduction

From a design perspective, the façade and cladding system is one of a building’s most crucial components. It helps to control condensation, safeguard the structure from bad weather, impede the spread of fire, and significantly affects energy efficiency. Despite its vital role, Facade and cladding design, specification, and installation have been the subject of several recent compliance difficulties in Australia. Well-publicized construction problems, building durability and occupant health have also been very important in recent times. That is why NCC has set specific requirements for facade regulated design that must be complied by designers.

It’s essential to have a complete grasp of the performance requirements and testing practices that affect façade and cladding systems. Working together from the beginning of the design development phase, when the details are being put together, is the ideal method to satisfy this performance need. The forward-thinking developers and builders will employ their own consultants to help the design team by creating project-specific information. This stage is crucial, especially if you want to deliver your project via design and construct.
So, in this article, we will outline the compliance pathways and test methods for the façade and cladding systems provided by the National Construction Code’s (NCC).

Façade’s Role in Buildings

The facade of a building serves several key functions, including:

1. Protection: The facade acts as a barrier between the interior of the building and the outside environment, protecting the building from weather, wind, and other environmental factors. It also helps to keep out unwanted noise and air pollution.
2. Aesthetics: The facade is an important architectural element that contributes to the overall appearance and design of the building. It can be used to create a sense of style, character and identity, and to reflect the building’s purpose and function.
3. Light and ventilation: The facade can be designed to control the amount of natural light and ventilation that enters the building. For example, by including windows, skylights, and other openings, the facade can help to provide natural light and ventilation, which can improve indoor air quality and reduce energy consumption.
4. Energy efficiency: The facade can also be designed to improve the energy efficiency of the building. For example, by using insulating materials, incorporating shading devices or by installing solar panels, the facade can help to reduce the amount of energy needed to heat and cool the building.
5. Security: The facade also plays a role in the security of the building, by providing a barrier that helps to protect the building from intrusions.
6. Durability: The facade materials should be durable enough to withstand the environmental conditions of the building location and the building usage.
7. Maintainability: The facade regulated design should also take into account the ease of maintenance and repair.

Facade Regulated Design in NSW

Facade regulated design in New South Wales (NSW), Australia is a set of guidelines and regulations that are put in place to ensure the safety and structural integrity of building facades. These regulations are enforced by the Building Code of Australia (BCA) and the NSW government through the Building Professionals Board.

Facade regulated design in NSW applies to buildings that are classified as “facade regulated buildings” as defined in the BCA. These include buildings that are more than three storeys in building height and that have a facade that is more than 15 meters in height, or that are classified as a “public building” under the BCA, such as a hospital, school, or aged care facility.

The regulations require that the design and construction of the facade of a building be carried out by a qualified and registered professional, such as an architect or engineer, who must demonstrate that the building’s facade meets the required safety and structural standards.

Facade regulated design in NSW also requires that the building owner conduct regular inspections and maintenance of the building’s facade, and that the building be retrofitted with safety measures if necessary.

The facade regulated design in NSW also requires that the building owner to report any defects, cracking or deterioration that may affect the safety of the facade to the relevant authorities.

NCC Compliance Pathways

NCC Vol. 1, Section A sets out three pathways for complying with Performance Requirements, specifically:

1. Performance Solutions.
2. Deemed-to-Satisfy Solution; or
3. A combination of Solutions

1. Performance Solutions

A performance solution is achieved by demonstrating compliance with all Performance Requirements or the solution is at least equivalent to the Deemed-to-Satisfy Provisions. A performance Solution must be shown to comply with the relevant Performance Requirements through one or a combination of the following Assessment Methods:

• Evidence of Suitability
• Verification Method
• Expert Judgement
• Comparison with the Deemed-to-Satisfy Provisions.

2. Deemed-to-satisfy solution

A Deemed-to-Satisfy Solution is achieved by following all appropriate Deemed-to-Satisfy Provisions in the NCC. The Deemed-to-Satisfy Provisions are prescriptive (i.e. like a recipe book, they tell you how, what and in which location things must be done). They include materials, components, design factors, and construction methods that, if used, are deemed to meet the Performance Requirements, hence the term “Deemed-to-Satisfy”.

3. A combination of solutions

Under Section A2.4 of NCC Vol.1, Performance Requirements may be satisfied by using a combination of both Performance Solutions and Deemed-to-Satisfy Solutions.

Performance Requirements

Structural Provisions (Section B)

According to BP1.1 in Section B of the NCC Vol. 1, a building or structure must function satisfactorily under all reasonably anticipated design actions and survive excessive or often repeated design actions during construction and usage for it to be considered reliable. The actions addressed by BP1.1 include dead loads, imposed loads, wind actions, thermal effects, earthquakes, snow, and earthquakes.

In B1.1 and B1.2, the DtS Solution for BP1.1 is offered. According to B1.1, the building’s resistance must be greater than the most important action effect coming from various combinations of actions. As per B1.2 and the general design guidelines in AS/NZS 1170, the action effect with the greatest potential for adverse consequences is identified. According to B1.4, a building or structure’s resistance is assessed.

B1.2 explains how the various components of AS/NZS 1170 are used to calculate the magnitude of each particular action.

Waterproofing Requirements (Section F)

FP1.4 of the NCC Vol. 1 outlines the weatherproofing requirements for facade and cladding systems. According to FP1.4, an external wall must stop water from penetrating that could result in unsanitary or hazardous circumstances, a loss of amenity for residents, excessive dampness, or the deterioration of building components. External walls are not covered by DtS Provisions under FP1.4, but FV1.1 outlines the testing process to determine whether an external wall complies.

Fire Resistance Requirements (Section C)

Under Section C of the NCC Vol. 1, buildings are required to have components, such as external walls, that prevent the spread of fire and maintain structural stability during a fire. These are found in CP1 to CP9 along with additional clauses pertaining to the protection of openings, the protection of service and emergency equipment, evacuation, and fire brigade access.

According to the DtS Provisions in C1.9, all external and common walls, as well as any components built into them, in buildings of Type A or B construction, must be non-combustible. Type of construction is determined by the building’s class and rise in storeys. Specification C1.1 of the NCC also states that the external walls of Type A and B buildings must be non-combustible, regardless of any fire rating requirements.

Compliance Test

Structural and Weatherproofing Tests

Procedures and standards for building structural design are outlined in AS/NZS 1170. The different sections of AS/NZS 1170 define the design values for use in structure design for wind, snow, ice, and earthquake actions, among other permanent, imposed, and other activities. As it relates to structural testing, AS/NZS 1170 defines two fundamental limit states: the Serviceability Limit State (SLS) and the Ultimate Limit State (ULS).

AS/NZS 4284:2008 Testing of building facades outlines the procedure for evaluating a façade system’s performance in terms of its structural stability and weather proofness. The AS/NZS:4284 technique is based on the SIROWET test, which was created by the CSIRO to handle wind-driven weather conditions that are expected to be encountered during the life of a structure. The AS/NZS 4284 weathertightness requirement examines if water is seeping through to the building’s interior and becoming evident on the internal surface of the facade.

The performance of a building facade under wind and other optional loadings is evaluated using a variety of tests under AS/NZS 4284. Tests comprise:

• Displacement/deflection test of façade/prototype.
• Wind Pressure and static/cyclic water pressure
• Structural testing for serviceability limit and ultimate limit
• Water penetration testing by static pressure followed by cyclic pressure
• Air infiltration.

Restraint of building maintenance units (BMUs), seismic loads, and seal deterioration are other tests.

Fire Tests

According to the NCC, a material is referred to be “non-combustible” if AS 1530.1:1994 Combustibility test for materials does not judge it combustible. AS 1530.1 recommends a small-scale test of submerging a sample for 30 minutes in a furnace maintained at 750°C. The material is considered combustible if:

• The material flames for 5 seconds or longer anytime during the test;
• The mean furnace thermocouple temperature rise exceeds 50 ̊C; and
• The mean specimen surface thermocouple temperature rise exceeds 50 ̊C.

A list of materials that may be utilised whenever a non-combustible substance is necessary is provided by the DtS Provisions in C1.9(e). For establishing if an exterior wall complies with CP2 to prevent the spread of fire, Verification Method CV3 is applicable when creating a Performance Solution. This Verification Method refers to the testing procedure in AS 5113:2016 Fire propagation test of exterior walls and contains extra sprinkler requirements. In the AS 5113 external wall test, two stories with an opening are simulated with various temperature measurements. The following criteria, among others, are part of the AS 5113 test requirements:

• no flame spread beyond the edge of the specimen.
• no flaming on ground (debris or molten material) for more than 20s; and
• not more than 2kg of fallen debris.

Other Tests

• Hail Impact Testing (ASTM E822)
• Cyclonic debris impact testing (AS 1170.2)
• Bushfire Attack Level (BAL) rating (AS1530.8.1:2007 and AS 1530.8.2:2007)

Conclusion

In conclusion, the façade and cladding system are vital components of a building, influencing its safety, energy efficiency, and aesthetics. To address compliance challenges and ensure building durability, the National Construction Code (NCC) has specific requirements for façade regulated design. Designers can choose between Performance Solutions and Deemed-to-Satisfy Solutions to meet NCC requirements. Various tests are conducted to evaluate the system’s performance, including structural, weatherproofing, and fire tests. In NSW, strict regulations govern façade regulated design, requiring qualified professionals and regular inspections. Adhering to NCC requirements is crucial for creating safe and visually appealing buildings that enhance occupant well-being and sustainability.

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