Smoke alarms: NCC rules for new work, state rules for existing homes

Editions covered: NCC 2022 (current in most states), NCC 2025 (WA, VIC, ACT), NCC 2019 noted; state law as held 2026-10-23 · Last reviewed 23 October 2026

Smoke alarms are covered by two layers of rules:

The NCC sets the rules for new houses and new building work.
State law decides what an existing home needs when it is sold, rented or renovated. This layer differs a lot from state to state.

This guide covers both, with the clause for each point, so electricians and builders can check a job quickly.

Which edition? NCC 2022 applies in NSW, QLD, SA, TAS and the NT. NCC 2025 applies in WA, VIC and the ACT from 1 May 2026. The NCC 2025 Housing Provisions list no change to Part 9.5.

Where the rules are

NCC 2022 Volume Two H3P2 and H3D6: compliance with ABCB Housing Provisions Part 9.5 satisfies the requirement. A Class 10a garage above or below the house counts as part of the Class 1 building (H3D6(2)).
AS 3786: the smoke alarm product standard (the NCC 2022 references the 2014 edition). We cite it by name only. Check the label on the alarm.
NCC 2019: the same rules sat in Part 3.7.5 (3.7.5.2 to 3.7.5.5).

Key requirements (NCC, new work)

Type, power and interconnection (HP 9.5.1):
- Alarms meet AS 3786.
- Where there is mains power to the building, they run on mains.
- Where there is more than one alarm, they are interconnected. This applies within one dwelling only.
- In a Class 10a garage, where smoke alarms would false-alarm, another alarm type suitable under AS 1670.1 (such as a heat alarm) can be used, provided AS 3786 smoke alarms are installed elsewhere in the house.
Locations in a Class 1a house (HP 9.5.2):
- On every storey with bedrooms: in each hallway or corridor serving bedrooms, or, if there is none, between the bedrooms and the rest of the house.
- On every other storey too.
Class 1b (boarding houses and similar) (HP 9.5.3): also in every bedroom.
Mounting position (HP 9.5.4):
- On or near the ceiling, at least 300 mm from the corner where the wall meets the ceiling.
- On a sloping ceiling, 500 mm to 1500 mm from the apex.
- If ceiling mounting isn't possible, on the wall, 300 mm to 500 mm below the ceiling.
Evacuation lighting: needed in Class 1b buildings only (HP 9.5.5).

How the states differ

Western Australia: Building Regulations 2012 rr 55 to 61 cover existing dwellings.
- Before sale the owner must have alarms meeting r 60(2) (r 56). If they don't, the new owner must fix it within 6 or 12 months (r 57).
- The same applies before renting, including short-term rental (r 58), and before hire (r 59).
- Under r 60(2), alarms must meet the NCC rules in force when they were installed, be in working order, and be within their expiry date (or under 10 years old). Where mains power was required, they must be hard-wired.
- A 10-year non-removable battery alarm is allowed where there is no hidden space to run cable, or where the local government approves it under r 61.
- Under r 60(4), homes whose building permit was applied for before 1 May 2015, or that were built under an earlier building licence, don't need interconnection.
New South Wales:
- NSW 9.5.1 (HP 2022) adds a heat alarm to AS 1603.3 in a garage under a garage-top dwelling that the garage doesn't belong to. It must be interconnected, and notices must be fixed in both places.
- For existing homes, the Environmental Planning and Assessment (Development Certification and Fire Safety) Regulation 2021, s 95, requires owners to have alarms on or near the ceiling in bedroom hallways and on every storey. In a Class 1b building they also go in each bedroom. That Part doesn't require interconnection.
- Landlords must replace alarms within 10 years of manufacture, or sooner if the maker says so (Residential Tenancies Regulation 2019, cl 20).
Queensland: Building Regulation 2021 Part 4 (ss 9 to 12) applies to building development applications for a new Class 1a home or a Class 2 unit.
- Each bedroom needs an alarm. Alarms must be photoelectric (not ionisation), comply with AS 3786–2014, be hard-wired and interconnected (s 11).
- Section 12 sets placement, including at least 300 mm from a light fitting and 400 mm from a ceiling fan's blades or an air-conditioning outlet.
- Existing homes are covered by the Fire Services Act 1990 (Qld), chapter 4A part 4 division 5A, and the Building Fire Safety Regulation 2008 (Qld), part 5A. Both apply to houses (Class 1a) and units (Class 2).
  - When a home is sold or a tenancy starts or is renewed, or after a substantial renovation (alterations to more than half the volume of the existing building), it must meet the full rules (s 147Z). Alarms must be photoelectric with no ionisation sensor and comply with AS 3786–2014 (Regulation s 55E). They must be interconnected and less than 10 years old when installed.
  - Alarms go in every bedroom, in the hallway or area between the bedrooms and the rest of the home on each storey with bedrooms, and on the path to the exit on other storeys. The mounting distances are the same as for new homes (Regulation s 55C).
  - Each alarm must be hard-wired, or have a built-in battery that can't be removed and lasts at least 10 years (Regulation s 55D). A hard-wired alarm must be replaced with a hard-wired one.
  - Owners must replace an alarm within 10 years of its manufacture date, or straight away if it fails its test (s 148A). A seller must tell the buyer in writing, by the date of possession, whether compliant alarms are installed (s 148I).
  - Landlords must test and clean the alarms, and replace flat batteries, in the 30 days before a tenancy starts (ss 148B, 148C and 148E).
  - The Act's separate section for other existing homes (s 147Y) expires on 31 December 2026.
South Australia: Planning, Development and Infrastructure (General) Regulations 2017, reg 95, covers Class 1 and 2 dwellings whenever they were built.
- Within 6 months of a title transfer, alarms must be mains-powered or have 10-year non-replaceable, non-removable batteries. The owner commits an offence if the required alarms aren't installed (reg 95(5)).
Victoria: Building Regulations 2018, reg 145, covers Class 1 homes built, or with a permit granted, before 1 August 1997. They must have "a smoke alarm system that complies with the deemed-to-satisfy provisions contained in clause H3D6 of the BCA Volume Two" or an approved mains-powered system (reg 145(2)).
Tasmania, the ACT and the NT: the NCC Part 9.5 rules apply to new work. Rules for existing or rented homes differ between these places, so check with your local authority.

Ask the app

Photograph the ceiling and alarm position and upload it, or ask:

"Do smoke alarms need to be interconnected in an existing house in WA?"
"Where do smoke alarms go in a two-storey house?"
"How far from the wall does a smoke alarm need to be?"
"Can I use a 10-year battery smoke alarm instead of hard-wired?"
"What smoke alarms does a NSW rental need?"

Ask an electrical question · Fire · Builder

Related checklists

Smoke alarms (Class 1): new house (plan required)
Smoke alarms (Class 1): renovation / extension (plan required)
Smoke alarms (Class 1): repair / maintenance (plan required)
Electrical: new house (plan required)
State pages: WA · NSW · VIC · QLD · SA · TAS · ACT · NT
Related guide: Balustrades and stairs

This is general guidance, not a compliance check. Always check your approved plans, the edition that applies to your permit and your state's current law, and confirm details with your certifier or building surveyor.

Based on content from the National Construction Code 2022 and 2025 (NCC Volume Two and the ABCB Housing Provisions), provided by the Australian Building Codes Board under the CC BY 4.0 licence. The ABCB does not endorse this guide. Based on content from the New South Wales Legislation website at 20 October 2026 (Development Certification and Fire Safety Regulation) and 22 October 2026 (Residential Tenancies Regulation). For the latest information on New South Wales Government legislation please go to https://www.legislation.nsw.gov.au. Based on content from the Queensland Legislation website at 14 October 2026 (Building Regulation 2021) and 23 October 2026 (Fire Services Act 1990 and Building Fire Safety Regulation 2008). For the latest information on Queensland Government legislation please go to https://www.legislation.qld.gov.au. The standards the NCC references are cited and explained in our own words, not reproduced.