Planning the electrical for a bathroom renovation

Bathrooms are where position matters most. The Wiring Rules set zones around showers and baths, and what can go in each, from switches and power points to light fittings and heaters, depends on how close it is to the water and how well it's protected. The upshot is that the electrical layout can't be finalised until the shower, bath and vanity are.

A frameless screen, a walk-in shower or a freestanding bath can change the zones compared with the old layout, so a point that was fine before may not be allowed now. Give your electrician a plan with the shower base, screen, bath and vanity dimensioned, and ask them to mark anything the zones rule out.

Portable heaters are the old bathroom hazard. Energy Safe Victoria says standard portable heaters shouldn't be used in bathrooms, and points to a strip heater installed high on the wall or a ceiling unit installed by a registered electrical contractor instead. A renovation is the time to build that in.

Steam has to leave the house, not just the room. Place the fan near the shower, away from the door so it draws air across the room, with a short, straight duct to an eave, wall or roof outlet. Venting into the roof space puts warm, wet air onto cold timber and insulation, where it condenses and feeds mould you can't see.

Switching is the usual failure. A fan on the light switch stops when you leave, just when the room is wettest. A separate switch with a run-on timer, or a humidity sensor, keeps it going until the steam clears. For an ensuite beside a bedroom, a quieter inline fan in the roof space is worth considering.

If the house still has an open-flued gas heater, two Energy Safe Victoria cautions apply. Running an exhaust fan while a gas heater is on can draw carbon monoxide into living spaces, and renovating or sealing up a home with an open-flued heater may change the ventilation it needs. Have the heater checked as part of the job.

A 3-in-1 unit puts heat lamps or a fan heater, a light and an exhaust fan in one ceiling fitting. It's tidy and warms the person under it quickly. The heater draws far more power than the light or fan, so the circuit has to carry it, and in a larger bathroom it warms you better than the room.

The alternative separates the jobs: a dedicated exhaust fan near the shower, a heater where you stand to dry off, and lighting on its own. It means more fittings, but each sits in its best spot, and a dedicated fan is usually stronger than the one inside a 3-in-1.

Either way, wire each function to its own switch, mark the heat switch clearly, and fix the unit between joists with the clearances its manual sets from insulation and timber. Mark the position on the frame before the ceiling is sheeted.

Heated towel rails come plug-in or hardwired. In a renovation, hardwired is neater and avoids a power point near the towels. The connection usually sits behind the rail, placed to suit its mounting points and the wet-area zones, so choose the rail and get its dimensions before rough-in.

A timer or a switch outside the wet zone stops the rail running all day; many people set it for the morning and evening showers. Check the manual for how the maker allows it to be switched.

Underfloor heating mats go under the tiles, so they're part of the waterproofing and tiling sequence. They need a controller, a floor sensor and power planned at rough-in, and the mat should be tested before and after tiling, since a damaged mat can't be fixed without lifting tiles.

Mirror cabinets with built-in lights, demisters or internal power need a supply behind the cabinet at the position its instructions set. Get the model and cut-out details before rough-in, because moving cable after tiling is a big job.

For shavers, toothbrushes and hair tools there are two options. A shaver outlet is made for bathrooms but only supplies small loads like shavers and toothbrushes. A standard power point suits hair dryers and straighteners, but must sit where the zones allow, often beside or inside the vanity rather than over the basin.

Think about where things charge and where they're stored. A toothbrush on the vanity, a hair dryer in a drawer and a cabinet that hides chargers all suggest points in different places, so mark them with the vanity drawings in front of you.

A single ceiling light behind you throws your face into shadow at the mirror. Light from either side of the mirror, or a lit mirror cabinet, is far better for shaving and make-up. Add general light from the ceiling and, if you like, a low night light on a sensor for late-night trips.

Fittings in wet areas need a rating to suit their position, shown as IP and two digits; the second digit is water protection, and higher is better. LED strip near a bath or shower needs sealed strip, with its driver kept well away from water. Put switches outside the zones, usually by the door, with ceiling lights, mirror lights and the fan on separate switches.

The usual order is strip-out, then plumbing and electrical rough-in together, then sheeting, waterproofing and tiling, then fit-off of the vanity, fixtures, fan, lights and towel rail. Electrical rough-in must be finished and checked against the final layout before the waterproofer starts, because nothing should be drilled through the membrane afterwards.

Talk to the tiler about point positions too. A towel rail outlet or mirror supply that lands across a grout line looks untidy, so agree heights in tile courses where you can.

When the job is done, the electrical work comes with a Certificate of Electrical Safety. A licensed electrician must provide one whenever they complete electrical installation work, and Energy Safe Victoria says the copy for work like lights and power points is due within 30 days.