The Bushfire Attack Level 'BAL LOW' is based on insufficient risk to warrant specific bushfire construction requirements. It is predicated on low threat vegetation and non vegetated areas.

However...

The Victorian Building Regulations (Items 157 & 158) state that a Class 1, 2, 3, 4, 9a, 9b or 10a building in a Bushfire Prone Area (BPA) must be built to a minimum of BAL 12.5.  

Refer to Section 5 - Construction Requirements for BAL 12.5.

A dwelling is a Class 1a building, and a shed, garage or carport is a Class 10a building.