Why is there a 4.5 tonne weight limit on tiny houses on wheels (THOW) in Australia?

There is a 4.5 tonne (4500kgs) weight limit on the use of electric brakes on any trailer or caravan in Australia. If a trailer or vehicle is rated to more than 4500kgs, it is legally required to have a non-electric braking system, for example an air-over hydraulic braking system, which adds an additional $5,200 upwards plus engineering costs, to the cost of the tiny house trailer.

As such, most tiny house builders (DIY and professionals alike) choose to stay within the 4500kgs weight limit for building their tiny house on wheels (THOW).