The year of construction is one of a number of criteria to determine how likely a home is to leak. There is a clear correlation between the date of construction and the degree of risk. This is obvious when comparing it against the changes of the Building Act, especially with regard to the use of treated/untreated timber for framing and the requirement for cavities between the external cladding and framing in houses with monolithic claddings.
The rule of thumb Before 1987: low to moderate risk 1987 - 1997: high risk 1998 - 2004: very high risk After 2004/2005: low to moderate risk (according to Prendos and other sources)