We're building a double-storey home in Geelong with bedrooms on both levels. Where exactly do the smoke alarms have to go, and do they all need to be interconnected?

Yes, they all need to be interconnected, and with bedrooms on both levels you need at least one alarm on each storey, positioned to serve each group of bedrooms. [1] [2]

Where they go. In a Class 1a dwelling, smoke alarms must be located: [2]

• on any storey containing bedrooms, in every corridor or hallway associated with a bedroom, or, where there is no corridor or hallway, in an area between the bedrooms and the rest of the building; and
• on each other storey, including a storey with no bedrooms.

Where bedrooms are grouped in separate areas of the house, each area needs its own alarm, which is the arrangement Figure 9.5.2b illustrates. [2]

What they must be. Every required alarm must: [1]

• comply with AS 3786;
• be powered from the consumer mains, where the building has a mains supply;
• be interconnected where there is more than one alarm, so that all of them sound together.

Interconnection applies within the one dwelling. The alarms don't have to be linked to another dwelling, or to a private garage that doesn't belong to it. [1] In a Class 10a private garage where a smoke alarm would give spurious alarms, another suitable alarm, such as a heat alarm, may be used there, provided AS 3786 alarms are installed elsewhere in the house. [1]

Where on the ceiling. Alarms go on or near the ceiling: [3]

• on a flat ceiling, at least 300 mm from the corner junction of the wall and ceiling;
• on a sloping ceiling, between 500 mm and 1500 mm from the high point or apex;
• where ceiling mounting isn't possible, on the wall, between 300 mm and 500 mm below the ceiling.

Victoria has been on NCC 2025 as the sole edition since 1 May 2026. These requirements read the same in NCC 2022. [4]