“From 1 March 2012 critical building work that is known as Restricted Building Work, must be done by an LBP (Licensed Building Practitioner).”
Restricted Building Work is “building work (including design work) that relates to either the structure (load-bearing walls; foundations etc) or moisture penetration (roofs; cladding etc) of homes including small to medium sized apartments… also includes the design of fire safety systems for small to medium apartments”
Designers, carpenters, external plasterers, bricklayers and blocklayers, foundation specialists, roofers and on-site supervisors or managers must all be registered as Licensed Building Practitioners. Registered Architects and Plumbers as well as Chartered Professional Engineers are also deemed to be licensed.
The go to site for all the official information is the Department of Building and Housing which has a special section for homeowners.