The electrical problems that cause real damage are almost never the ones you can see.
A dead power point announces itself. A breaker that trips gets your attention. But the faults that start fires have usually been developing quietly for years behind plaster, above ceilings and inside walls, and there’s nothing in the house to tell you.
Here are five we find regularly in Melbourne homes that looked completely fine from the inside.
1. Perished rubber-insulated cable
Homes wired between roughly the 1930s and 1960s used rubber-insulated cable, often with a cotton braid over it. Rubber has a service life, and it’s shorter than the houses.
Over decades — especially in a Melbourne roof space that hits 60 degrees every summer — the rubber hardens, cracks and eventually crumbles away from the conductor. What’s left is bare copper sitting in a cavity full of dry timber, dust and insulation.
Why you won’t spot it: the outlets and switches all work perfectly. The circuits carry load. Nothing on your switchboard looks unusual. The failure happens above the ceiling.
How it’s actually found: someone with a torch in the roof space. That’s it. It’s why we get up there during a safety check.
What it means: if your home still has original rubber-insulated wiring, that’s a full rewire conversation, not a repair. Patching one section of a failing system buys you very little.
2. Pest damage to cabling
A distinctly Australian problem, and far more common than most homeowners would like.
Possums live in roof spaces across the eastern suburbs. Rats and mice live in wall cavities. All of them chew cable — not out of malice, just because that’s what rodents do to keep their teeth in order.
The result is damaged insulation and exposed conductor in exactly the location where a spark is least welcome.
Why you won’t spot it: the damage is above you. Often the circuit keeps working fine, because the conductor is intact even though the insulation isn’t.
The clues: you’ve had pest activity, you hear movement in the roof at night, or you’ve noticed a circuit behaving intermittently for no obvious reason.
What to do: deal with the pests, then have the wiring inspected. Doing the second without the first just gives them fresh cable.
3. Bad joints inside walls and ceilings
Every renovation leaves electrical work behind, and not all of it was done by someone licensed.
What we find: conductors twisted together and wrapped in electrical tape, buried in a wall cavity. Junction boxes with no lid. Cables joined inside a ceiling with no enclosure at all. Circuits extended off a lighting point to feed a whole new room.
A poor joint has resistance. Resistance under load generates heat. Heat, over years, degrades everything around it. This is one of the most common origins of electrical fires in homes, and it is completely invisible from the room.
Why you won’t spot it: the light turns on. Everything appears to work.
The clues: a circuit that trips occasionally with no clear cause, a light that flickers intermittently, or — the big one — the knowledge that previous owners did their own renovations.
What to do: if you’ve bought a house with obvious owner-builder history, get the wiring inspected properly rather than assuming it’s fine because the lights work.
4. No RCD protection, and no idea
We covered this in the safety check article and it’s worth repeating here because it’s so widespread.
Plenty of Melbourne homes have had ceramic fuses swapped for circuit breakers at some point, and stopped there. The board looks modern. The owner reasonably assumes it’s been brought up to standard.
But circuit breakers protect the wiring, not people. They’ll let through many times the current needed to kill someone. RCDs — safety switches — detect current leaking to earth and disconnect in about 30 milliseconds. They’re the device that actually saves a life.
How to check in ten seconds: look at your switchboard for buttons marked “T” or “Test”. No buttons, no protection.
What to do: a switchboard upgrade with RCD protection across all final subcircuits. It’s the highest-value electrical work most older homes can have done.
And if you have RCDs, test them. Press the button every three months. An RCD that doesn’t trip is worse than no RCD, because everyone in the house believes they’re protected.
5. Undersized or deteriorated consumer mains
The cable running from the street or the meter into your switchboard. Nobody thinks about it, and in a lot of older homes it hasn’t been touched since the house was built.
Modern households draw dramatically more current than the ones these cables were sized for. Add ducted air conditioning, an induction cooktop, a heat pump and an EV charger to a house whose mains were specified in 1965, and the cable is running much closer to its limit than anyone intended.
Why you won’t spot it: it’s behind the meter panel. There’s no indicator for it.
The clues: lights dimming noticeably when large appliances start, a persistent sense that the supply is struggling, or a meter panel that’s warm to the touch. That last one is urgent.
What to do: a meter panel upgrade and, where needed, new consumer mains. Worth doing before you electrify rather than after — see our guide to switching from gas to electricity.
The common thread
All five of these share the same characteristic: the house gives you no warning. Everything works. Nothing looks wrong. And then one day it isn’t fine any more.
The only way to find them is for someone to look — in the roof, in the board, behind the meter panel.
When it’s worth having a look
If you’ve just bought an older home. Building inspections rarely include a meaningful electrical assessment.
If the house hasn’t been inspected in a decade or more.
If you’re renovating. Ceilings down and walls open is the cheapest access you’ll ever have.
If you’re about to electrify. Find out what you’re working with before you add load to it.
If there’s been pest activity.
An inspection takes an hour or so and you get a straight list: what’s fine, what should be done eventually, what should be done soon. If everything’s fine, we’ll say so.
Talk to us
Registered Master Electrician (REC 25989). Over 200 five-star Google reviews. Lifetime workmanship warranty on everything we do.
We work across Melbourne’s eastern suburbs from Hawthorn — a lot of beautiful old houses, and a lot of wiring that’s older than anyone realises.
Related: The 7 most common electrical problems in Melbourne homes · Smoke alarms and safety checks