Lighting plans

Understanding the basics

The three layers of light

Good lighting design uses three distinct layers that work together.

Reading the symbols on a plan

Lighting plans use standardised symbols that your electrician will know but that can appear cryptic at first. A circle with a cross typically denotes a ceiling-mounted light. A circle with a dot in the centre often represents a downlight. Wall-mounted fittings are shown as a small rectangle or half-circle on the wall line. Switch symbols appear as an S with a diagonal tail, with additional tails indicating two-way or intermediate switching.

Circuit lines connect fixtures to their switch points and are usually shown as dashed or curved lines rather than straight ones, to distinguish them from structural elements. If your architect or designer has not included a legend on the plan, ask for one before the electrical rough-in meeting. Without a legend, it is easy for a homeowner and electrician to interpret a symbol differently.

Colour temperature and CRI

Colour temperature, measured in Kelvin (K), describes how warm or cool a light source appears. Bulbs in the 2700–3000 K range produce a warm white that suits living rooms, bedrooms, and dining areas. The 3500–4000 K range gives a neutral white that works well in kitchens and home offices. Anything above 5000 K is a cool daylight tone, more common in commercial and retail settings.

Colour Rendering Index (CRI) measures how accurately a light source renders colour compared to natural daylight, on a scale of 0 to 100. For most residential applications, specify a minimum CRI of 90. Lower-CRI lamps make paint colours and finishes look different from how they appeared in the showroom or sample, which is a frequent source of disappointment after handover.

Brightness: lumens, not watts

With LED, watts tell you how much power a fitting draws, not how bright it is; brightness is measured in lumens. A modern LED produces roughly 80–110 lumens per watt, so a 9 W downlight might deliver 800–1000 lumens. Judge and compare fittings on their lumen output, and ignore the old habit of thinking in watts (a "60 W-equivalent" lamp simply means it produces about 800 lumens).

Plan the total lumens a room needs rather than counting fittings. As a rough guide, aim for around 250–300 lumens per square metre of general ambient light in living and bedroom areas, rising for task zones: a kitchen bench or bathroom mirror wants noticeably more light directed onto the work surface. These are starting points; dimming lets you bring a well-lit room down, but no dimmer can add light that was never specified, so it is safer to plan slightly generous and dim back.

Beam angles and downlight spacing

Two downlights of identical wattage can light a room completely differently depending on beam angle. Specifying a narrow beam for general light leaves dark gaps and spotlit patches; specifying a wide beam for an accent washes out the effect. The beam angle is fixed when you order, so it must be decided up front.

For even ambient coverage, a common rule of thumb is to space downlights at roughly half the ceiling height apart, about 1.2 m apart on a standard 2.4 m ceiling, in a regular grid, keeping the perimeter row set off the walls as described under setout. Resist the urge to over-pepper the ceiling with fittings: a layered plan of fewer, well-placed downlights plus lamps and task lighting reads far better than a uniform grid of dozens of recessed lights.

Wet areas and outdoor ratings

Bathroom IP zones

Lighting near water is governed by the AS/NZS 3000 wiring rules, which divide a bathroom into zones and set a minimum ingress-protection (IP) rating for fittings in each. The IP rating has two digits: the first is protection against solids, the second against water, so the water digit is what matters here (4 = splashing from any direction, 5 = water jets, 7 = temporary immersion).

This is a compliance and safety matter, not a styling choice. Your electrician must select fittings to suit the zone. Confirm the IP rating of any bathroom light, exhaust-light, or shower downlight against the zone it will sit in before ordering.

Outdoor and covered areas

Exterior fittings carry an IP rating too. A fitting under a well-protected eave or covered alfresco can usually be IP44, but anything exposed to direct rain, such as facade lights, garden spikes, or uncovered entries, should be IP65 or higher. Marine or pool-side environments push the requirement higher again. Specify the rating per location on the plan rather than assuming one "outdoor" fitting suits everywhere.

Circuit zoning

How circuits are grouped

Each lighting circuit runs from your switchboard to a group of fittings that share the same on/off control. How your electrician groups fittings into circuits determines how flexibly you can control your lighting later. If an entire open-plan living, dining, and kitchen area is wired as a single circuit, you cannot dim the dining pendant without also dimming the kitchen downlights.

As a general rule, group fixtures by zone and function rather than by room boundary alone. In an open-plan space, the kitchen bench lights, the island pendant, the dining pendant, and the living ambient downlights should each be on separate circuits or at least separate dimmer channels.

Dimming and scene control

Not all LED fittings are dimmable, and not all dimmers are compatible with all LEDs. If you intend to dim a circuit, you must specify dimmable fittings and an LED-compatible dimmer at the same time, from the outset. Installing a standard dimmer on a non-dimmable LED will cause flicker, buzzing, or early fitting failure.

Scene control systems, such as Casambi, Clipsal C-Bus, or Lutron, allow you to save and recall preset light levels across multiple circuits from a single switch or app. These systems require additional investment upfront but deliver considerably more flexibility than individual dimmers on each circuit. If you are considering a scene control system, the rough-in stage is the time to run the necessary cabling, even if you do not install the controllers until later.

Switching logic

Two-way and multi-way switching

A two-way switch allows you to control a single circuit from two locations, the most common example being a staircase light that can be turned on at the bottom and off at the top. To control the same circuit from a third (or further) location, an intermediate switch is wired between the two-way switches, an arrangement described as "two-way and intermediate" switching, and it suits long hallways, large living areas, or any room with more than two entries. (Note the terminology trap: what Australia calls a two-way switch is sold as a "three-way switch" in North America, so confirm the standard before ordering imported fittings.)

Walk through your floor plan and identify every room or passageway where you will enter and exit from different points. Bedrooms with an ensuite, combined living and dining areas with multiple entries, and any hallway longer than about four metres are prime candidates for multi-way switching. Failing to specify this at rough-in means additional wiring runs later, which invariably involves opening walls or running surface conduit.

Common switch placement mistakes

Switches placed on the wrong side of a door are one of the most common and most irritating installation errors. The switch should be on the side from which you approach the room as you open the door, so that your hand naturally lands on it as you enter. In practice, this means identifying the swing of each door and positioning the switch on the latch side, not the hinge side.

Height consistency also matters. AS/NZS 3000 does not fix a switch height, but residential switches in Australia are commonly installed around 900–1100 mm from finished floor level, and accessible (Livable Housing) design favours the lower end, often aligned with the door-handle height. If your electrician installs switches at varying heights across the house, the inconsistency will be noticeable. Agree on a standard height at the outset and confirm it before any switches are mounted.

Outdoor and sensor switching

Outdoor lighting is often underspecified in renovation lighting plans. Consider how the exterior of the property will be lit for security, amenity, and aesthetics separately. Security lighting near entry points benefits from passive infrared (PIR) sensors with a dusk-to-dawn override. Pathway and garden lighting is often better served by a dedicated circuit on a timer or photocell rather than a manual switch that is regularly left on overnight.

Sensor switches in internal spaces, such as motion sensors in laundries, garages, or storerooms, are practical but require the fitting to be rated for frequent switching cycles. Standard LED downlights are generally suitable; some driver-based fittings have minimum-on-time requirements that make them unsuitable for sensor switching. Confirm with your electrician and fitting supplier before specifying.

Briefing your electrician

When to have the lighting conversation

The lighting conversation must happen before rough-in, not after. Rough-in is the stage at which your electrician runs cables through open wall and ceiling cavities, before linings are installed. Once plasterboard is up and painted, adding or moving a circuit requires cutting, patching, repainting, and potential damage to adjacent finishes. The cost of a change at rough-in is a fraction of the cost of the same change at lock-up or after handover.

If your project includes a designer or architect, they should provide a lighting plan before rough-in begins. If you are managing the project yourself, prepare your own annotated version of the floor plan showing every fitting, its intended circuit, its switch location, and whether it needs to be dimmable. Hand this to your electrician at least a week before rough-in is scheduled so they can price and order any non-standard components.

What to specify in writing

Verbal instructions to trades are frequently misremembered or not passed on to apprentices. For lighting, confirm in writing the following for each circuit:

Setout dimensions matter more than many homeowners realise. A downlight positioned roughly 300 mm from a wall reads as a deliberate wall-wash detail; the same downlight set 600–800 mm from the wall reads as a general ambient fitting. If your designer has specified setout distances, make sure they are noted on the plan and confirmed with the electrician, not assumed.