Compliance with the Building Code
Although the Building Code is a performance-based system, it does allow for the use of prescriptive solutions in order to achieve compliance. Several ways of meeting the requirements of the Building Code have been published. Any building constructed in accordance with the methods described in a Verification Method or Acceptable Solution must be accepted by the building consent authority (BCA) as complying with the Building Code.
There is at least one Verification Method or Acceptable Solution for each of the technical clauses in the Building Code. In most cases, the Verification Methods and Acceptable Solutions do not quantify the requirements of the Building Code directly. Instead, they cite qualified sources such as New Zealand standards to establish performance benchmarks.
Verification Methods describe calculations and tests that can be used to evaluate a proposed design against the requirements of the Building Code. Verification by calculation might use analytical methods and mathematical models to assess the proposed design. Verification by testing might require laboratory confirmation of the proposed techniques and materials and an empirical examination of the design.
Acceptable Solutions describe prescriptive methods that can be followed to meet the requirements of a particular clause of the Building Code. They usually provide simple step-by-step instructions, which guarantee compliance if followed correctly. Although they are widely used in residential construction, Acceptable Solutions are by no means compulsory and are just one way to comply with the Building Code.
Alternative methods and Alternative Solutions
Designers are free to choose any Verification Method or Acceptable Solution they like to achieve compliance with the Building Code, or they can choose another method entirely. These are referred to as alternative methods. An alternative method can differ from the Verification Methods and Acceptable Solutions as much as the designer chooses.
However, the building owner (or the owner's agent, such as an architect, engineer or builder) must demonstrate that it meets the performance requirements of the Building Code to the satisfaction of the BCA. One way to establish compliance with the Building Code is by comparison with the equivalent performance level set in Verification Methods or Acceptable Solutions (equivalence).
Once it receives building consent, an alternative method becomes an Alternative Solution.
In practice, the process to verify that an alternative method meets particular provisions of the Building Code usually requires detailed investigation and will often require peer review. MBIE outlines the process for using an Alternative Method here and in the Building Code Handbook.
The Ministry of Business, Innovation and Employment maintains the complete set of Verification Methods and Acceptable Solutions on its website. The documents for clause B1 Structure are particularly relevant to seismic resilience. Check the website periodically, as MBIE issues frequent updates.