Here's the thing nobody tells you: the expensive mistakes happen before a single wall comes down.
Whether you're building from scratch or taking on a big renovation, there are so many decisions to make up front. Get them right the first time and you'll save yourself money, stress and a lot of "if only" down the track.
Yet most people call a designer once the builders have already started. By then, the plumbing, the windows and the power points are all locked in. Changing them isn't impossible, but it's rarely cheap.
So my one big tip? Do the thinking first. It's a lot cheaper on paper than fixing it on site.
Why your builder shouldn't be making your design decisions
Let me be clear: a good builder is worth their weight in gold. But a builder's job is to build what's on the plans, on time and on budget. Designing how you'll actually live in the space isn't their brief.
When the plans leave gaps, those gaps still get filled. They just get filled quickly, on site, often with whatever's standard or easiest. That's how you end up with:
A power point hidden behind where your bed or sofa needs to go
A single pendant dead centre in a room that needed layered light
Plumbing that dictates your vanity size, rather than the other way around
Windows that fight your furniture layout or leave no wall for art
And once you want to change something mid-build, it becomes a variation. The NSW Government's Consumer Building Guide says “Any change to your contract is a variation, it must be in writing and signed by both parties”, and you can guarantee it will most likely impact the contract price.
So if you want to save yourself money……Make the decisions before the contract and the build, not during!
The decisions to make before you build
These are the ones I see people wish they'd thought about sooner. Each is easy to change on paper and hard to change on site.
How you'll live in each room. Start with your furniture layout, not the floor plan. Where does the bed go? The sofa? The dining table? Everything else flows from this.
Power points and switches. Map them to your furniture plan: bedside charging, TV walls, kitchen appliances, desk spaces, outdoor areas.
Lighting. Plan task, ambient and accent light room by room, before the electrician's rough-in. (More on that in my post on planning lighting before plastering.)
Plumbing positions. Decide on vanity widths, tap styles, shower layouts and kitchen sink placement before pipes go in.
Windows and doors. Check sizes and positions against your layout, your views and where you'd like art or storage to sit.
Joinery and storage. Built-ins affect wall positions, power and lighting, so they need to be in the plan early.
Finishes and fixtures. Tiles, flooring and tapware can have lead times. Choosing early helps avoid rushed swaps when something's out of stock.
How a designer helps before you build
Bringing a designer in early isn't about adding another cost. It's about doing the thinking while it's still cheap to change your mind.
Here's what that looks like with us:
We start with how you live. Your routines, your family, your furniture and the way you want each room to feel.
We plan on paper first. Furniture layouts, lighting, power and plumbing positions, all mapped out before trades arrive.
We help you see it. 3D visuals mean you can walk through your home before it exists and change things with a click, not a sledge hammer.
We work with your builder. Less guesswork on site means fewer surprises and fewer variations.
We're in your corner. You get someone whose only job is making sure the finished home works for YOU.
Let's start with a conversation
If you're planning a build or renovation, the best time to call a designer is before your plans are locked in. The second-best time is NOW.
Book a design consult with RCD Interiors and we'll talk through your plans, flag anything worth rethinking and help you make those big decisions with confidence. No pressure, no jargon, just a clear head before the hammers start.
Missed the Weekly Q&A this tip came from? Catch it on Instagram and follow along for a new one each week. Rx
Frequently asked questions
When should I hire an interior designer for a new build or renovation? As early as possible, ideally before your plans are finalised and before you get a building quote. That's when layout, power, lighting and plumbing decisions are still cheap to change. Builders quote PC (prime cost) items based on estimates, so if you want an accurate quote, your materials, fixtures and fittings should all be locked in before you go to tender.
Can't my builder just make these decisions for me? Your builder builds what's on the plans. Where the plans leave gaps, choices often get made quickly on site. A designer fills those gaps around how you actually want to live.
What happens if I change my mind during the build? In NSW, any change to your building contract is a variation. It must be in writing, signed by both parties, and almost all variations affect the contract price.
What will we cover in a design consult? We'll talk through your plans, how you want to live in the space, and flag any decisions worth locking in before building starts.
Reference
NSW Government, Consumer Building Guide (Version 2025, page updated 19 February 2026)