Recently I was lucky enough to have a conversation with the most senior technical advisor of Timber Queensland. His expertise in roof tie-downs is second to none. He lives in Queensland – home of the most extreme weather systems in our country.
He was able to articulate our country’s building regulation history with ease and it went something like this…
In 1979 (post Tracey and a few other notable cyclones to hit Australia) Colin wrote the first of many documents that stated “a rule of thumb” approach to constructing homes in Queensland. With reference to a “bank book”, banks adopted these first construction codes by releasing progress payments to bank customers through mortgage agreements. This was the beginning of construction regulation. New builds would now have to build with anchor rods to connect the roof to the walls of a building – if you needed help from the banks.
Many amendments have been made since then as engineering has evolved and damage to the number of buildings has become more prevalent. Following various construction codes has always been under state and territory jurisdiction. However, since the creation of the National Construction Code where the Council of Australian Government adopted building regulation on a national scale, state and territories agreed that a national compliance/standard was the way to go.
The AS1684 is the primary reference document that outlines acceptable construction when talking about roof tie downs. This can be used as a minimum requirement document to satisfy the NCC-BCA. Engineer specification is considered a performance solution and is acceptable on par or higher than using AS (Australian Standard) documents when designing construction. The most current amendment of AS1684 is the 2010 reference. All construction in Australia is by law, required to follow this standard as a minimum if the building details aren’t specified by an engineer. Although roof tie-downs are periodically revised and vitality has varied due to wind classification areas, they have been considered an essential part of building practice for about the past 40 years – according to AS1684. Now, more than ever, a national emphasis is weighted on tie-downs because of extreme weather events.