TL;DR
The national rule: every Class 1 dwelling needs smoke alarms complying with AS 3786-2014, installed on every storey, in the hallway serving the bedrooms, powered from the mains where mains power is supplied, with a standby battery, and interconnected where there is more than one alarm. In NCC 2022 the clause is Part 9.5 of the ABCB Housing Provisions, called up by Part H3 of Volume Two. For Class 2 to 9 work it is Part E2 and Specification 20 of Volume One.
Interconnection is not new. It has applied to new Class 1 dwellings and to sole-occupancy units in Class 2, 3 and 4 buildings since 1 May 2014. Wired or wireless both count.
Photoelectric is not an NCC requirement. AS 3786 covers photoelectric and ionisation. Queensland legislation mandates photoelectric only. Every Australian fire service recommends it.
The NCC does not require an alarm inside a bedroom. Queensland does.
Existing dwellings are state law, not the NCC, and the rules differ a lot. Queensland's final deadline for all remaining owner-occupied homes is 1 January 2027.
The one nobody diarises: every alarm has a 10-year replacement life, printed on the back.

If you have been building houses for a while, the smoke alarm requirements Australia works to feel like the simplest part of the job. Two alarms in the hallway, sparky wires them in at fit-off, done. The trouble is that the rules have moved three times in the last decade, they now split into a national set for new work and seven different sets for existing homes, and the bit that catches people is rarely the alarm itself. It is the placement, the interconnection, and the paperwork proving the alarm that went in was the alarm the code asked for.

This guide covers what the NCC requires and where the clause sits, the placement rules certifiers actually pick up, photoelectric versus ionisation, how interconnection works in practice, the state by state position on existing dwellings, and a set of FAQs at the end.

What the NCC requires, and where the clause actually lives

For houses, townhouses and any other Class 1 building, the smoke alarm provisions sit in Part 9.5, Smoke alarms and evacuation lighting, in the ABCB Housing Provisions, which Volume Two calls up through Part H3. If you learned the numbering as 3.7.5, or 3.7.2 before that, it is the same material renumbered in the NCC 2022 restructure. For Class 2 to 9 buildings, including apartments, motels and boarding houses, it is Part E2 of Volume One with the technical detail in Specification 20.

Four requirements, and all four are testable on site:

• The alarm complies with AS 3786-2014.
• It is installed in the locations the clause nominates, on every storey.
• It is powered from the consumer mains where mains power is supplied to the building, with a standby battery.
• Where more than one alarm is required, they are interconnected, so one alarm activating sounds all of them.

The ABCB publishes Part 9.5 free online, figures included, and it is worth reading the two diagrams rather than working from memory.

One note on editions. The current edition is NCC 2025, released on 1 May 2026, and adoption is staggered: Victoria, Western Australia and the ACT from 1 May 2026, Queensland, New South Wales, South Australia's building volume and Tasmania from 1 May 2027, and the Northern Territory still assessing under NCC 2022. So a fair slice of the country is still being assessed against NCC 2022. The smoke alarm provisions were not one of the areas this edition was built around, but confirm the clause in the edition your approval is actually assessed under. Our volume by volume rundown of the current NCC edition has the wider change list, and NCC fire safety requirements in plain English covers how alarms sit alongside fire separation and egress.

Where the alarms go, and the placement misses that fail an inspection

The location rule is about paths of travel, not about rooms. On a storey containing bedrooms, an alarm goes in every corridor or hallway associated with a bedroom, or, where there is no corridor or hallway, in the area between the bedrooms and the rest of the dwelling. On a storey with no bedrooms, the alarm goes in the path of travel occupants would take to leave.

That is the part most builders have right. Here is the part that gets picked up:

• Alarms go on or near the ceiling, and a ceiling-mounted alarm must be a minimum of 300 mm clear of the corner junction of wall and ceiling. That dead air in the corner is where smoke arrives last.
• On a sloping or raked ceiling, the alarm sits between 500 mm and 1500 mm from the high point or apex. Too close to the apex and it sits in a hot air pocket. Too far down the rake and the smoke layer passes above it. If you build raked ceilings regularly, this is the single most common placement fault.
• Grouped bedrooms served by one hallway get one alarm in that hallway. Bedrooms split either side of a living area are two separate hallways and two separate alarms, not one in the middle.
• A garage under a garage-top dwelling that is not associated with that dwelling has its alarms interconnected to the dwelling above.

Mark the positions on the plan at frame stage, not on the day of fit-off. An alarm 200 mm off a corner is a rework that needs a ceiling patch, a repaint and a second sparky visit.

Photoelectric or ionisation, and why every fire service picks one

This is where the code and the best practice part company, and it is worth being clear about which is which.

The NCC does not mandate photoelectric. It requires compliance with AS 3786, and AS 3786 covers scattered light (photoelectric), transmitted light and ionisation types. An ionisation alarm can be fully code compliant for new work in most of the country.

The two technologies do different jobs. A photoelectric alarm typically responds at around 8 to 16 per cent obscuration per metre. An ionisation alarm typically responds between 40 and 60 per cent. That gap matters because of the fires that kill people at home: smouldering upholstery, a failed power board, overheated wiring in a cavity. Those produce smoke for a long time before they produce flame, and a slow smoke build-up is exactly the case an ionisation alarm is worst at. Ionisation alarms are also the ones that go off when somebody makes toast, which is how alarms end up with the battery pulled out.

Every Australian fire authority recommends photoelectric for residential use. Queensland went further and wrote it into law. If you are specifying for a client, spec photoelectric and write the reason on the quote. It is a few dollars a unit and it is the easiest good decision on the whole job.

A 2023 revision of AS 3786 has been published. What binds you is the version your NCC edition or state legislation calls up, and that is currently AS 3786-2014 in both the NCC and the Queensland rules. Check the marking on the product before you buy a pallet of them.

Interconnection, hard wiring, and who is allowed to do the install

Interconnection means one alarm detecting smoke sounds every alarm in the dwelling. It has been a requirement for new Class 1 dwellings, and for sole-occupancy units in Class 2, 3 and 4 buildings, since 1 May 2014. Two points that come up constantly:

• Interconnection is per dwelling, not per building. Alarms in one unit of a duplex do not interconnect with the alarms next door.
• Wired or wireless both satisfy it. Wireless RF base units are the practical answer in a retrofit where you are not opening ceilings. Keep the whole dwelling on one brand and one family. Mixing manufacturers is the reason a retrofit set does not pair, and there is no standard that makes brand A talk to brand B.

On power, the rule is mains where mains is supplied, with a standby battery. That makes a mains-powered alarm install or replacement licensed electrical work in every state and territory. AS/NZS 3000, the wiring rules, deals with how the circuit is run and how the interconnect conductors are treated. Owner-builders in particular need to be clear on this: an owner-builder permit does not carry an electrical licence, and swapping a hardwired alarm yourself is unlicensed electrical work. If you are working through what an owner-builder can and cannot self-perform, our owner builder Australia guide covers the permit and insurance side.

Cost varies too much by state, ceiling access and alarm count to put a number on it here. Get a real quote from your sparky, and remember it carries GST like any other trade line, so a $900 allowance is $990 to the client.

Smoke alarm requirements Australia state by state, on existing dwellings

New work follows the NCC. Existing dwellings are governed by state legislation, and that is where the map goes patchy. This is a summary to orient you, not legal advice, and tenancy rules in particular get amended often. Confirm against your own regulator before you quote a compliance upgrade.

• Queensland. The strictest by a distance. Photoelectric only, AS 3786:2014, less than 10 years old, interconnected, in every bedroom, on every storey, and in hallways connecting bedrooms to the rest of the dwelling. New and substantially renovated dwellings since 1 January 2017. Sold or leased dwellings since 1 January 2022. All remaining owner-occupied homes by 1 January 2027. The Queensland Fire Department page is the authority.
• Victoria. Dwellings approved after 1 August 1997 require 240V mains-powered alarms with battery backup. Older dwellings may use battery-powered alarms.
• New South Wales. At least one working alarm on every storey of any residential building where people sleep. No photoelectric or interconnection mandate for existing homes. Tenancy law adds landlord duties, including repairing a reported faulty alarm within two business days.
• South Australia. New builds from 1 January 1995 needed hardwired alarms, and existing buildings had to comply by 1 January 2000. On a change of ownership on or after 1 February 1998, the new owner has six months from title transfer to install either 240V hardwired alarms or alarms with a 10-year non-replaceable, non-removable battery. See the SA MFS legislation fact sheet.
• Western Australia. Under the Building Regulations 2012, compliant mains-powered alarms must be installed before a dwelling is sold, transferred, rented or hired, and they must be not more than 10 years old at that point. A 10-year sealed battery alarm is permitted in limited situations where mains connection is not practicable. Details at Building and Energy WA.
• Tasmania. Alarms required in hallways outside bedrooms and on each level. In rentals, since 1 May 2016, alarms must be mains-powered or have a 10-year non-removable battery. A replaceable-battery alarm does not meet the rental requirement.
• ACT and NT. New work follows the NCC. Neither carries a Queensland-style retrofit programme for existing owner-occupied homes as far as we can confirm, so treat the NCC plus the 10-year replacement life as the floor and check with the territory regulator on anything you are contracting to.

Queensland's deadline matters outside Queensland

Two reasons to care about 1 January 2027 even if you never work north of the border.

First, the market. Queensland's staging has pulled national supply toward interconnected photoelectric units, which is why wireless base RF alarms are now easy to get and reasonably priced everywhere. Second, the direction of travel. Queensland's rule started as a new-build requirement in 2017, extended to sold and leased dwellings in 2022, and lands on every remaining home in 2027. That is the pattern other jurisdictions look at when they review their own regulations. Speccing interconnected photoelectric alarms on a renovation today is the version you will not have to redo.

The 10-year rule, and the handover pack that proves you did it

Every smoke alarm has a service life of 10 years, and the manufacture or expiry date is printed on the back of the unit. The sensor degrades whether or not the alarm has ever been triggered, so a unit that beeps when you press the button can still be past its useful life. In WA the 10-year age limit is written into the requirement at sale or rental. In Queensland it is part of the compliance definition.

For a builder, that turns into three small habits:

1. Photograph the label on each alarm before it goes up, with the manufacture date legible. That photo is your proof of AS 3786 compliance and of the age.
2. Photograph the installed positions, so the 300 mm corner clearance and the rake position are on record.
3. Put the electrical certificate of compliance and the alarm model into the handover pack, and hand the client a note with the replacement year on it. Ten years is two owners away. Nobody remembers.

Keeping that on the phone as you go, rather than reconstructing it at practical completion, is the whole difference. If you are weighing up how to hold job photos, certificates and defect items in one place instead of three group chats, we keep an honest rundown of construction project management software for Australian builders.

Frequently asked questions

Does the NCC require a smoke alarm inside every bedroom?
No. The NCC requires alarms in the hallway or corridor serving the bedrooms, or between the bedrooms and the rest of the dwelling where there is no hallway, plus one on every storey. Queensland legislation does require an alarm in every bedroom, which is the biggest single difference between the national rule and the Queensland rule. Fire services recommend bedroom alarms everywhere regardless.

Can I use battery-only alarms in a new house?
Not if mains power is supplied to the building, which it is on essentially every new house. The NCC requires the alarm to be powered from the consumer mains with a standby battery. Battery-only alarms remain legal in some existing dwellings, depending on the state and on when the dwelling was approved or last changed hands.

Do interconnected alarms have to be wired to each other?
No. Wired and wireless interconnection both satisfy the requirement. Wireless is usually the sensible choice in an existing home where you would otherwise be cutting ceilings. Keep every alarm in the dwelling the same brand and compatible family, because there is no cross-manufacturer pairing standard.

I am renovating an older home. Do I have to bring the whole house up to current requirements?
It depends on the state and on the scope. Queensland's rule bites on a "substantial renovation" and applies to the whole dwelling. Elsewhere the trigger is usually the scope of the building approval, so new or altered parts must comply while untouched parts may not be captured. Ask your certifier before you price it, and if the answer is borderline, price the full upgrade as a clearly itemised option rather than absorbing it later.

How do I tell when an alarm is due for replacement?
Read the back of the unit. The manufacture date or expiry date is printed there, and the service life is 10 years from manufacture. Test monthly with the button, vacuum the vents a couple of times a year, and replace the whole unit at 10 years even if it still sounds. A mains-powered replacement is a job for a licensed electrician.

One less thing to reconstruct at handover

None of this is hard to build. It is hard to prove two years later when a client asks, or when a certifier wants the model, the date and the position on a job you finished in March. Alarms are a five-minute item that turns into an afternoon of scrolling through photos.

Built Simple is free to download on the App Store and Google Play, and all 45 calculators work on the phone without a signup. Keep your alarm label photos, your certificates and your fit-off positions against the job instead of in a group chat, and the handover pack writes itself. More building, less admin.