This ‘fact sheet’ was developed by the Australasian Bat Society:
The document below was developed by the LaTrobe Valley Field Naturalists, La Trobe City Council, and the West Gippsland Catchment Management Authority. It’s full of useful information relevant to Victorian microbats:
Probably the easiest and cheapest box to make yourself is the Kent Bat Box:
Here are some slightly more complicated design specs for bat boxes (using imperial measurements instead of metric) developed by Bat Conservation International (USA).
Simple, single chamber bat box design:
Four-chambered bat box design:
Some general info and recommendations for building and installing bat boxes developed by Bat Conservation International for the USA, but still generally applicable to Australia:
Here are some bat box resources developed by the Bat Conservation Trust (UK).