The One Lighting decision You Can't Undo after the plaster goes up!
There's a moment in every renovation where lighting quietly stops being a choice. The framing's up, the electrician's on site, and someone asks "so, where do you want your downlights?" — and whatever gets answered in that thirty-second conversation is what you'll live with for the next twenty years.
By the time the plaster's on, that decision is set. Moving a light later means cutting open a finished ceiling, re-patching, re-painting, and paying for the privilege. Most people don't do it. They just live with lighting that's almost right — and never quite understand why the room feels off.
This post is about timing and why lighting has to be planned earlier than almost anyone expects, and what it costswhen it isn't.
Why Lighting happens at "Rough-In," Not a Finishing Touch (in any renovation)
In building terms, wiring goes in at rough-in — before insulation, before plasterboard, before the walls are closed. That means every decision about where light comes from has to be made while the house is still a skeleton.
The problem: lighting feels like a finishing touch. It sits in your head next to paint colours and tapware — things you choose late. So it gets left late. But by then the walls are closed, and the cheap, flexible stage has already passed.
The mismatch in one line: you have to commit to your lighting when the space looks nothing like the room you're imagining.
What Actually Gets Locked In at Rough-In
Once the plaster's on, these are effectively permanent without cutting into finished surfaces:
Where every ceiling light sits — downlights, pendants, feature fittings.
Where the switches live — and whether they're where your hand actually reaches on the way into a room.
How lights are grouped — which fittings turn on together, and what's on its own circuit.
Whether a fitting can dim — dimming often depends on wiring and driver choices made now, not the globe you buy later.
Wall lights, reading lights, stair lighting — anything needing a cable in a wall.
None of these are things you want an electrician guessing on your behalf while you're at work.
The Hidden Cost of Deciding Late
Leaving it to the on-site conversation doesn't usually cause a disaster. It causes a hundred small compromises that add up to a room that underperforms:
Lights centred on the room, not the furniture — so your sofa, bed or island sits in shadow while the light pools over the walkway.
The dreaded downlight grid — evenly spaced dots that light the floor beautifully and the people not at all.
Switches in awkward spots — the ones you reach past a doorframe in the dark to find.
One big switch for everything — no ability to soften a room for evening, because it was all wired to a single circuit.
No dimming where you most want it — discovered the first night you try to relax in the living room.
Individually, minor. Together, it's the difference between a room that works and one that just… doesn't, in a way most people can never quite name.
The Sequence That Saves You
The fix isn't spending more — it's deciding earlier. A lighting plan should exist before the electrician walks on site, not be improvised once they're there.
That plan is driven by two things most people haven't finalised yet at first-fix stage:
Your furniture layout — because light follows function. Where the bed, sofa, island and reading chair land determines where the light needs to be.
How you actually use each room — morning routines, evening wind-down, where you cook, read, work.
Nail those two early and the lighting almost designs itself. Leave them vague, and someone else fills the gap with a default grid.
Where This Connects to the Bigger Picture
Getting the timing right is step one. Getting the plan right — how bright each room should be, which fittings suit which job, how to handle wet areas safely — is the next layer, and it's worth doing properly before you commit anything to the ceiling.
That's exactly what our free guide, Lighting Your Interiors, walks you through: the three layers of light, a room-by-room brightness guide, and where safety ratings actually matter. If you're renovating or building, read it before your first-fix stage — it's designed to be used at exactly the moment this decision lands.
Sign up below to receive the Free Guide → The layers, the numbers and the wet-area rules, everything you need to plan your lighting before the plaster goes up.
Lighting is one of the first decisions we work through in every project. See our interior design services, or book a design consultation to plan yours properly