Building Code and B2
The Building Code sets out performance standards that building work must meet. It has 35 technical clauses covering requirements such as managing external moisture, structure and ventilation. Clause B2 is the technical clause for durability and includes timber treatment. It sets out the durability requirements for all building elements.
An Acceptable Solution details one way to comply with the relevant part of the Building Code. If you follow this method, your building work will meet that part of the Building Code. B2/AS1 is an Acceptable Solution for clause B2 (Durability) of the Building Code.
There can be ways of complying with the Building Code other than through an Acceptable Solution - these are often called alternative solutions.
This is a hazard class for timber treatment. A hazard class defines the risk and the level of timber treatment, as specified in NZS 3640 and NZS 3602.
This describes the exterior surfaces (wall cladding, roofing, windows and doors) of a building.
For full details check B2/AS1