Yes. I have divided this into 3 areas – Road Regulations, Gas and Electrics.
Road : There is a system of National Standards for vehicles know as ADRs (Australian Design Rules) in addition to a large number of Australian Standards. However the best source of practical info for ‘Building a Small Trailer ‘ is called VSB1- short for Vehicle Standards Bulletin. VSB1 operates as an alternative to the ADRs and applies for all trailers with an ATM of up to 4500kgs. It contains info on lights, wiring, brakes, draw-bars, axles, dimensions etc etc.
It is the responsibility of the Manufacturer to ensure the trailer meets the standards set out in VSB1. So well worth downloading a copy and having it avaialable as a reference during your build.
Gas : In addition if your Caravan is to have any gas appliances (LPG) then these must be installed by a licensed LP Gas Fitter and certified with a Gas System Compliance Certificate which complies with the Australian Standard for gas compliance AS5601.
Electrics: Also if you have any 240 volt installation then this should comply with AS/NZS 3000. DIY recommends having a fully qualified electrician carry out the 240 V installation and provide a certificate of compliance on completion.