Every NSW home must have a working smoke alarm on each storey, made to Australian Standard AS 3786. Newly built homes and most major renovations must use 240V hardwired alarms with battery backup, interconnected so that all of them sound together. Every alarm, hardwired or battery, expires 10 years after its manufacture date and has to be replaced.
Which of those rules bites depends on when your place was built, whether you have renovated, and whether anyone rents it.
Where does NSW law require smoke alarms?
NSW has required working smoke alarms in every building where people sleep since 1 May 2006. That covers owner-occupied houses and units, rentals, relocatable homes, caravans and campervans, and it does not lapse with age. An 80-year-old cottage that has never been touched still needs working alarms.
The minimum is one working alarm on every storey, including levels without bedrooms, placed in the hallway serving the bedrooms or, where there is no hallway, between the bedrooms and the rest of the home. Alarms must be made to AS 3786, and anything sold legally in Australia carries that marking on the back.
Do smoke alarms need to be hardwired?
It depends on when the home was built or last substantially renovated. The Building Code has required mains-powered 240V alarms with battery backup in new homes since 1 August 1997. Homes built before then may generally keep battery-only alarms, provided they work and meet AS 3786.
The trigger most people run into is renovation. Once building work needs approval, alarms in the affected part of the home usually have to come up to current code, which means hardwired. Worth sorting early rather than at final inspection, and a good reason to book an electrical check before renovating.
A 240V alarm runs off the home's fixed wiring, normally a lighting circuit from the switchboard, with a backup battery for blackouts. An old, full board can quietly become the obstacle when there is no safe way to add the circuit, in which case a switchboard upgrade gets done as part of the same job.
| Alarm type | Powered by | Where it is accepted |
|---|---|---|
| Battery only, replaceable battery | 9V battery, changed yearly | Existing homes built before August 1997 and not substantially renovated |
| Battery only, sealed 10-year lithium | Non-removable battery lasting the life of the alarm | Same as above, and easier because there is no yearly battery change |
| 240V hardwired with battery backup | Mains power from the switchboard, battery takes over in a blackout | Required in new builds and most approved renovations. Legal anywhere as an upgrade |
What are interconnected smoke alarms, and when are they required?
Interconnected alarms are linked so that when one detects smoke, every alarm in the home sounds at once. Distance is the reason. A fire starting in the garage may set off one alarm that nobody in a front bedroom can hear through a closed door.
The Building Code requires interconnection in new homes where more than one alarm is fitted, which covers nearly every new build and most approved renovations. NSW does not force existing homes to retrofit, so in a decades-old unrenovated house, working alarms on each storey still satisfy the law.
It is still the upgrade most worth doing voluntarily. Two methods link alarms:
- Hardwired interconnection. A signal wire runs between alarms. Most reliable and standard in new builds, but it needs cable pulled between fittings, so it suits a renovation or rewire.
- Wireless interconnection. Alarms talk by radio instead, which suits retrofitting a finished home where cable would mean cutting ceilings open.
Mixing brands is the usual mistake: interconnection is not a universal standard, so alarms from two manufacturers generally will not pair even when both are wireless.
Getting smoke alarms sorted properly?
DM Electrical installs and replaces 240V hardwired and interconnected smoke alarms across the Northern Beaches, North Shore, Eastern Suburbs and wider Sydney, and can tell you on site whether your switchboard has room for the circuit. Based in Brookvale, available 24/7.
How often should smoke alarms be replaced?
Every smoke alarm must be replaced 10 years after its date of manufacture, however well it appears to work. The sensing chamber degrades with dust, humidity and age, so a 12-year-old alarm can still pass a button test while no longer detecting smoke reliably. The button confirms the horn and the battery, not the sensor.
The date is printed on the back, so the alarm has to come off the ceiling to read it, and it is the manufacture date rather than your install date. If there is no readable date, treat the alarm as expired, because an unmarked unit is almost always an old one.
- Monthly: press the test button on each alarm and listen for a strong, clear sound.
- Every six months: vacuum the outside with a brush attachment to clear dust and insects from the vents.
- Yearly: replace the removable battery, if it has one.
- At 10 years: replace the whole alarm, hardwired ones included.
Intervals like this are easy to lose track of across several properties, in the same way test and tag intervals are. Writing the replacement date on the alarm in marker when it goes up saves the guesswork later.
Photoelectric or ionisation, and does it matter?
Fire and Rescue NSW recommends photoelectric alarms, and that is the type worth fitting. They detect the visible smoke a slow, smouldering fire produces, which is the most dangerous residential case. Ionisation alarms react faster to flaming fires but slower to smouldering smoke, and they nuisance-trip more on cooking and steam. NSW law does not mandate a type, so ionisation remains legal, but when you are buying anyway photoelectric is the better choice.
What do landlords have to do in NSW?
Landlords carry the legal duty for smoke alarms in a rented property, and the obligations tightened on 23 March 2020. A landlord must check alarms yearly and repair or replace a faulty one within two business days of finding out. Removable batteries must be changed yearly, and alarms replaced within 10 years or by their expiry date.
Tenants must let the landlord or their tradesperson in to do this work, and must not remove or disable an alarm. Smoke alarms are one of the clearer lines in a murkier question, so if you are working out who pays for electrical repairs in a rental, this one sits with the owner. NSW Fair Trading publishes the current rental rules if you manage property.
Who can install a hardwired smoke alarm?
A 240V smoke alarm is fixed wiring, so it must be installed by a licensed electrician. A battery-only alarm you can swap yourself; the moment mains power is involved it is licensed work. On a typical job the electrician confirms how many alarms are needed and where, checks the switchboard can carry the circuit, runs the wiring, mounts and pairs the alarms, then tests every unit together. Where circuits are new or altered you should also receive a Certificate of Compliance for Electrical Work.
Cost depends more on access than on the alarms. A single-storey home with a crawlable roof space is straightforward; a two-storey home with concrete ceilings, or a full board needing upgrading first, is not. Expect anywhere from a few hundred dollars for a simple replacement up to a four-figure job for a full multi-alarm install, quoted on site rather than over the phone.
Frequently asked questions
Are interconnected smoke alarms mandatory in NSW?
Interconnected alarms are required by the Building Code in new homes where more than one alarm is installed, and in most renovations significant enough to need approval. NSW does not require existing homes to be retrofitted, so working alarms on each storey still meet the law in an older, unrenovated house. Interconnection is still the most worthwhile voluntary upgrade, because it means an alarm in the garage wakes someone in a back bedroom.
Can I replace a hardwired smoke alarm myself?
No. A 240V hardwired smoke alarm is connected to the home's fixed wiring, so replacing one is licensed electrical work and must be done by a licensed electrician in NSW. You can change the backup battery in a hardwired alarm yourself, and you can replace a battery-only alarm yourself, but anything involving the mains connection is not a DIY job.
Why does my smoke alarm chirp every minute?
A single chirp repeating every 30 to 60 seconds is usually a flat battery, including the backup battery in a hardwired alarm. If a fresh battery does not stop it, the alarm has most likely reached the end of its life and is signalling a fault, which is common as units approach 10 years old. Chirping across several alarms at once usually means the whole set is due.
The bottom line
Working alarms on every storey is the legal floor in NSW and applies to every home regardless of age. Hardwired 240V alarms are required in new builds and most approved renovations, interconnection comes with them, and every alarm expires at 10 years whatever its type. If your place is older none of that is forced on you, but linked photoelectric alarms still buy the most time in a fire. Get in touch and we will tell you what yours needs.