How the NCC Performance-Based System Operates

The National Construction Code (NCC), comprising the Building Code of Australia (Volumes One and Two) and the Plumbing Code of Australia (Volume Three), is a performance-based code. This means that it defines how buildings, building elements, and plumbing and drainage systems must perform to achieve the mandatory Performance Requirements. The requirements are built around a hierarchy consisting of four levels.

The benefit of having a performance-based NCC is that it provides practitioners with a strong degree of flexibility to determine the most appropriate means for demonstrating compliance with the relevant Performance Requirements.

Compliance can be shown by either:
• Complying with the Deemed-to-Satisfy Provisions;
• Formulating an Alternative Solution; or
• A mixture of Deemed-to-Satisfy Provisions and Alternative Solutions.

If compliance with the Deemed-to-Satisfy Provisions is chosen, the building solution will be deemed to have complied with the relevant Performance Requirements.

If an Alternative Solution is chosen, the practitioner must ensure that an Assessment Method is chosen which satisfactorily indicates that the Alternative Solution will meet the relevant Performance Requirements. The nature of the Assessment Method will vary depending on the complexity of the Alternative Solution.

The performance-based BCA was drafted following consideration of numerous overseas models (including the New Zealand, British, Swedish, and Dutch examples) to suit the Australian building regulatory environment. This has meant that the performance-based BCA substantially includes the technical requirements from the previous BCA90, with a ‘performance hierarchy’ built around them.

Hierarchy of the Building Code of Australia

The following is an explanation of the terms used and how they operate in practice.

Level One – Objectives
These represent the reason the community wants a matter regulated. They are primarily expressed in general terms, and usually refer to the need to safeguard people and protect adjoining buildings or other property. An example of an Objective from the BCA is:

“The Objective is to safeguard the occupants from injury or loss of amenity caused by inadequate height of a room or space.”

Level Two – Functional Statements
These set out in general terms how a building could be expected to satisfy the Objectives (or community expectations). An example of a Functional Statement from the BCA is:

“A building is to be constructed to provide height in a room or space suitable for the intended use.”

Level 3 – Performance Requirements
These outline a suitable level of performance which must be met by building materials, components, design factors, and construction methods in order for a building to meet the relevant Functional Statements and, in turn, the relevant Objectives.

The Performance Requirements are the core of the BCA and are the only parts of the code with which compliance is mandatory. An example of a Performance Requirement in the BCA is:

“A room or space must be of a height that does not unduly interfere with its intended function.”

Level 4 – Building Solutions
This level sets out the means of achieving compliance with the Performance Requirements. The BCA provides for two methods that can be followed to develop a Building Solution, as detailed at Levels 4a and 4b, below.

At Level 4a are the Deemed-to-Satisfy Provisions. These include examples of materials, components, design factors, and construction methods which, if used, will result in compliance with the Performance Requirements of the BCA. An example of a Deemed-to-Satisfy Provision in the BCA is:

“Ceiling heights must be not less than 2.4 metres in a habitable room.”

At Level 4b are the Alternative Solutions. The key to the performance-based BCA is that there is no obligation to adopt any particular material, component, design factor or construction method. An approval authority may still issue an approval if it differs in whole or in part from Deemed-to-Satisfy Provisions described in the BCA if it can be demonstrated that the design complies with the relevant Performance Requirement.

Hierarchy of the Plumbing Code of Australia

The performance-based PCA, as Volume Three of the NCC, is based on a similar performance hierarchy to Volumes One and Two. This provides for consistency in the operation of both the BCA and PCA.

The following is an explanation of the terms used and how they operate in practice.

Level One – Objectives
These represent the reason the community wants a matter regulated. They are primarily expressed in general terms, and usually refer to the need to safeguard people from illness, injury or loss of amenity etc. An example of an Objective from the PCA is:

“Safeguard people from illness, injury, or loss (including loss of amenity) due to the failure of a cold water installation”

Level 2 – Functional Statements
These set out in general terms how a plumbing or drainage solution could be expected to satisfy the Objectives (or community expectations). An example of a Functional Statement from the PCA is:

“Sanitary fixtures, sanitary appliances and supply outlets provided with drinking water must have safe and adequate piped cold water supply.”

Level 3 – Performance Requirements
These outline a suitable level of performance which must be met by plumbing and drainage materials, components, design factors and construction methods in order for a plumbing or drainage solution to meet the relevant Functional Statements and, in turn, Objectives. An example of a Performance Requirement from the PCA is:

“A cold water service must be designed, constructed and installed in such a manner as to provide water to fixtures and appliances at flow rates and pressures which are adequate for the correct functioning of those fixtures and appliances under normal conditions and in a manner that does not create undue noise.”

Level 4 – Plumbing or Drainage Solutions
This sets out the means of achieving compliance with the Performance Requirements. The PCA provides for two methods that can be followed to develop a plumbing or drainage solution, as detailed at Levels 4a and 4b, below.

At Level 4a are the Deemed-to-Satisfy Provisions. These include examples of materials, products, design factors, installation and construction methods which, if used, will result in compliance with the Performance Requirements of the PCA. Currently, many, though not all, of the prescriptive Deemed-to-Satisfy technical solutions which can be used to meet the requirements of the PCA are set out within the AS/NZS 3500 series of Australian Standards.

At Level 4b are the Alternative Solutions. The key to the performance-based PCA is that there is no obligation to adopt any particular design factor or construction method. A regulatory authority may still issue an approval if it differs in whole or in part from the Deemed-to-Satisfy Provisions described in the PCA if it can be demonstrated that the solution complies with the relevant Performance Requirement.