PERTHDo your smoke alarms have to be interconnected in WA?
Interconnection is required for newer WA homes and not for older ones. The cut-off is 1 May 2015, and it is the building permit application date rather than
Interconnected alarms all sound together. One detects smoke in the laundry and every alarm in the house goes off, which matters at three in the morning at the far end of a hallway with the door shut.
Whether your house needs them comes down to a single date.
The cut-off
Interconnection is not required for a dwelling constructed on an application for a building permit made before 1 May 2015.
Read that phrasing carefully, because two things in it catch people out.
It is the building permit application date, not the date the slab went down and not the date you moved in. A house applied for in March 2015 and finished in 2016 sits on the old side of the line. If you are not sure, the local government holds the permit records for your address.
And it is a requirement on construction, not on sale. Unlike the mains-power rule, interconnection is not triggered by the house changing hands. An older home can be sold with alarms that are not interconnected, and it is compliant.
Which does not make it a good idea
This is the part where the regulation and the sensible answer part company, and it is worth being honest about the difference.
A single-storey house built in 1974 with three hard-wired alarms that do not talk to each other meets the law. It also means a fire starting in the garage end may not wake anyone at the bedroom end until it is well established. The rule is a floor, not a recommendation.
Interconnection can be done by radio frequency rather than by wire, so the retrofit does not mean lifting ceilings. On a house that is already having alarms replaced for the ten-year rule, the incremental cost is small, and it is the single cheapest safety upgrade available to most Perth homes.
New builds
If you are building now, interconnection is required and it will be in the specification. Where it is worth checking is at handover, because "interconnected" is a claim that is easy to make and easy to test — press one alarm and stand in another room.
That test takes ten seconds and it is on the list at every practical completion inspection we do.
What we report
On a pre-purchase inspection we record how many alarms there are, where they are, whether they are hard-wired, their age where the date is legible, and whether they are interconnected. Then we tell you which of those are legal obligations and which are simply a good idea, because conflating the two helps nobody.
Related: why battery alarms usually fail the test when you sell, and the short-stay rules that changed in 2024.
What interconnection actually does
The value of interconnected alarms is easiest to understand by picturing the failure it prevents. In a house with stand-alone alarms, each unit only knows about the smoke directly beneath it. A fire that starts in a rear laundry at two in the morning sets off the laundry alarm, but that single alarm, two or three closed doors and a hallway away from the bedrooms, may not be loud enough to wake someone in a deep sleep at the other end of the house. By the time the smoke reaches the bedroom alarm, the fire has had several extra minutes to grow, and in a house fire minutes are the whole margin between getting out and not.
Interconnected alarms remove that gap. When one alarm senses smoke, every alarm in the house sounds at once. The laundry fire triggers the alarm above the bed on the first breath of smoke, not the fifth. That is the entire point of the requirement, and it is why the regulations increasingly push new and substantially renovated homes toward interconnection rather than treating it as an optional upgrade. The technology to do it is not exotic, and on a new build the cost of wiring the alarms together is trivial against the safety margin it buys.
Hard-wired and wireless interconnection
There are two ways alarms talk to each other, and it is worth knowing the difference because it changes what is practical in an existing house. Hard-wired interconnection runs a dedicated wire between the alarms so that the trigger signal travels along the cable. It is the standard approach in new construction, where the walls are open and running the extra conductor is straightforward, and it is completely reliable because there is nothing to pair or lose connection with. In a finished house, though, running that interconnect wire through existing walls and ceilings can mean lifting insulation, cutting access holes, and patching afterwards, which is where the cost climbs.
Wireless interconnection solves that. The alarms are still mains-powered, but they signal each other by radio rather than by wire, so retrofitting interconnection into an existing home no longer means opening up the ceilings. For a Perth homeowner upgrading an older house, wireless interconnected alarms are usually the practical answer: you get the whole-house response of interconnection without the disruption of running cable through a lived-in home. The units cost a little more each, but the installation is far simpler.
When the requirement is actually triggered
Interconnection is not retrospectively required on every existing home in the state. The obligation attaches at particular trigger points, principally new building work and substantial renovations that require a building permit, where the standard for the work being done pulls in the current alarm requirements. A house built to the rules of its era is not suddenly non-compliant because the standard moved on; but the moment significant permitted work is done, the current requirements come into play for that work.
This matters most to two groups. Anyone building or substantially renovating should expect interconnection to be part of the electrical scope, and should confirm it is specified rather than assuming it. And anyone buying a home that has been recently renovated should not assume the renovation brought the alarms up to the current standard, because whether it did depends on the scope of the permit and how carefully the work was done. An inspection reports what is actually installed and how the alarms are configured, which is the only way to know rather than guess.
Why we report the configuration, not just the count
When we inspect a house, the smoke alarms get more than a headcount. We report whether they are mains-powered or battery, whether they appear to be within their service life, where they are located relative to the bedrooms and the storeys, and whether they are interconnected. That last point is the one buyers most often have no information on, because interconnection is invisible from the ground: two houses can have the same number of identical-looking alarms on the ceiling, and in one of them they all sound together while in the other each is an island. On a house you are about to buy and sleep in, that is worth knowing, and it is the kind of detail that a compliance-minded inspection surfaces rather than leaves to a hopeful assumption.
The small cost against the large consequence
It is worth stating plainly what interconnection costs and what it buys, because the two are so far out of proportion that the decision is close to obvious once the numbers are in front of you. A set of wireless interconnected mains-powered alarms for a typical house is a modest job for an electrician, done in a morning, and the units themselves are a small premium over stand-alone alarms. Against that sits the thing the interconnection exists to prevent: a fire that starts in a part of the house away from where people are sleeping, and alarms that fail to raise the sleepers in time because each one only knows about its own patch of smoke. There are very few safety upgrades in a house where the cost is so small and the potential consequence so large, which is why the regulations keep moving in the direction of requiring it and why we treat its presence or absence as worth reporting on rather than as an optional nicety.
Common questions
Do old houses in WA need interconnected smoke alarms?
No. Interconnection is not required for a dwelling constructed on an application for a building permit made before 1 May 2015.
Is it the build date or the permit date?
The building permit application date. A house applied for in March 2015 and completed in 2016 sits on the older side of the line.
This comes up on every pre-purchase building inspection and practical completion (pci) inspection we carry out.
Read next: selling a house in WA? Your battery smoke alarms probably aren't legal and short-stay smoke alarm rules changed.
Sources
Read rather than recalled. Summarised here; the documents themselves are Crown copyright and are linked rather than reproduced.