Picture this. You’re standing in your kitchen on a Saturday morning, coffee in one hand, kid’s school bag in the other, and somebody’s elbow in your ribs. The house you loved five years ago has quietly shrunk. Funny how that happens.
So you start Googling. And you land here, asking the big question: what does a house extension actually cost in Wollongong?
Short answer? Most single-storey extensions around here land somewhere between $2,500 and $5,000 per square metre. A 40 sqm extension, for example, usually comes in around $100,000 to $200,000. Premium finishes or a tricky site can push past $6,000 per square metre.
That’s a wide range, I know. It’s a bit like asking “how much is a car?” Which car? Where? With what extras? So let’s unpack it properly, in plain English, with no builder-speak.
The Quick Numbers: House Extension Cost Wollongong (2026)
Before the detail, here’s the cheat sheet. These are ballpark figures to help you plan. Your real price depends on your site, your design and your finishes.
| Type of project | Typical cost range | What you’re getting |
| Single-storey extension (per sqm) | $2,500 – $5,000 | Standard finishes, built and fitted out |
| Single-storey extension (40 sqm) | $100,000 – $200,000 | A decent living area or main bedroom suite |
| Second-storey addition | $250,000 – $600,000 | Adding a whole level on top |
| Knock-down rebuild | $450,000 – $1,000,000+ | Starting fresh |
Sources for these figures are listed at the end of the post. Treat them as guides, not quotes.
One more thing. Another Australian guide puts ground-floor extensions at roughly $2,000 to over $4,000 per square metre nationally. So you’ll see different numbers online. That’s normal. Wollongong sits in the middle of the pack, and what you build matters more than the postcode.
Why Is the Price Range So Wide?
Here’s the thing nobody tells you at the start. “Per square metre” is a shortcut, not a promise.
Think of it like a restaurant menu that says “mains from $25 to $65”. Both are dinner. One has a steak with a sauce you can’t pronounce. Extensions work the same way.
Here are the big things that move your price.
1. What kind of room you’re adding
A bedroom is simple. Four walls, a window, power points. Easy.
Kitchens and bathrooms are the expensive ones. They need plumbing, waterproofing, electrical work and lots of fixtures, and those need specialist trades. So a 20 sqm kitchen extension will cost a lot more per square metre than a 20 sqm rumpus room.
2. Your site (this is the Illawarra wildcard)
Wollongong isn’t flat, tidy land. We’ve got escarpment views, sloping blocks, sandy coastal soil and the odd creek running where you’d least expect it.
A sloping block often means more excavation, retaining walls or deeper footings. That adds cost. I’ve seen a lovely back garden with a gorgeous view turn out to be a pretty serious engineering exercise. Worth it? Usually, yes. But you want to know before you sign.
3. Single or double storey
Going up costs more in total, but not always per square metre. Why? Because you’re sharing the foundations and roof across two levels. A second-storey addition runs far higher overall ($250,000 to $600,000 is the typical range), but you’re getting a whole new floor.
4. Finishes and fittings
Laminate benchtops or stone? Standard windows or big stacking doors? Engineered timber floors or polished concrete? Every upgrade nudges the price up. None of it is wrong, but it adds up faster than you think.
5. How easy your house is to connect to
Joining a new extension to an old house can be smooth. Or it can be a surprise party where the guest of honour is old wiring, unexpected asbestos or a wall that isn’t where the plans say it is. That’s why every sensible budget has a buffer.
House Extension Cost Wollongong: A Real-World Example
Let’s make this less abstract. Here’s a rough budget for a 40 sqm single-storey rear extension (open-plan kitchen and living) on a standard block.
| Item | Rough cost |
| Design and drawings | $8,000 – $18,000 |
| Council or certifier fees and approvals | $3,000 – $10,000 |
| Structural engineering and surveys | $3,000 – $8,000 |
| Building work (40 sqm at mid-range rate) | $100,000 – $160,000 |
| Kitchen fit-out (if not included above) | $20,000 – $50,000 |
| Landscaping repair and extras | $5,000 – $15,000 |
| Contingency (10 – 15%) | $15,000 – $25,000 |
These are my rough planning figures for budgeting, not a quote. Some items overlap with the per-square-metre rate depending on what your builder includes.
See what happened there? The “building cost” is the big number, but it’s far from the only one. People who budget only for the build get a nasty shock around month three.
What’s Usually Included (and What Isn’t)?
This is where quotes get confusing. Two builders can give you prices $30,000 apart and both be honest. The difference is often what’s in the quote.
Usually included in the per-square-metre rate:
- Footings and slab
- Framing and roof
- Walls, insulation and plastering
- Standard windows and doors
- Basic electrical and plumbing
- Painting and standard flooring
Often NOT included (so ask!):
- Architect or designer fees
- Council or private certifier fees
- Soil testing and surveys
- Kitchen and bathroom fit-outs beyond a standard allowance
- Landscaping, fencing and driveway repairs
- Air-conditioning
- Temporary accommodation if you move out
My honest advice? Ask every builder for an itemised quote. If somebody hands you a single number on a napkin, politely run. Okay, maybe not run. But ask a lot of questions.
The Hidden Costs of a House Extension (The Ones That Bite)
I’ll be straight with you. Nobody enjoys this section, but it’ll save you money.
Professional fees
You’ll need a few experts before a single brick moves. As a guide, builders charge around $90 to $150 an hour for extension work, surveyors roughly $90 to $170 an hour, structural engineers about $90 to $190 an hour, and architects roughly $100 to $250 an hour. Those hours add up quickly on a complicated design.
Approvals
Depending on your project, you’ll go down one of two paths in NSW. Smaller, simpler jobs may qualify as complying development, which is usually quicker. Bigger or more complex projects need a development application (DA) through Wollongong City Council. Either way, you’ll pay fees, and you’ll wait. Wait times are the real cost here, honestly.
Wollongong has some quirks to watch for: bushfire-prone land near the escarpment, flood-affected areas, coastal zones and heritage overlays. Any of these can mean extra reports and extra design requirements. Check your property early.
Insurance and licensing
In NSW, a builder doing residential work over $20,000 needs to arrange home building compensation insurance for you. That’s a good thing. It’s a safety net if your builder disappears or goes under. Make sure they show you the certificate before work starts. And check their licence on the NSW Fair Trading website. It takes two minutes and could save you a world of grief.
The “while we’re at it” effect
You open a wall. You see the old wiring. You think, “Might as well fix that.” Then the bathroom looks tired next to the new kitchen. Then you want new flooring all the way through.
It’s the single most common way budgets blow out. I call it extension creep. Good news: you can plan for it. Set aside 10 to 15 per cent as a buffer, and you’ll sleep better.
Extension vs Second Storey vs Rebuild: Which Makes Sense?
This is the question I get asked most, usually with a slightly panicked look.
- Single-storey extension: Best if you’ve got yard space and the existing house is in good shape. Usually the best value per dollar.
- Second-storey addition: Best if your block is small or you want to keep your garden. It costs more overall, but you don’t lose any outdoor space.
- Knock-down rebuild: Best if the house is tired, the layout is awkward and you’d be fixing problems forever. It costs the most up front, but you get a brand-new home.
A rough rule of thumb many builders use: once a big renovation creeps toward 60 to 70 per cent of the cost of a rebuild, it’s worth pricing the rebuild too. Sometimes the numbers surprise you.
How Long Does a House Extension Take?
Money isn’t the only currency. Time matters too, and it’s worth knowing what to expect.
| Stage | Rough timeframe |
| Design and drawings | 4 – 10 weeks |
| Approvals (council or certifier) | 4 – 16 weeks |
| Construction (single-storey) | 3 – 6 months |
| Construction (second storey) | 5 – 9 months |
Weather, material delays and trades’ schedules can stretch these. A rainy Illawarra winter has a way of testing everyone’s patience. Build some flexibility into your plans, especially if you’ve got a date in mind, like a baby due or Christmas lunch for 20.
7 Practical Ways to Keep Your Extension Cost Down
You don’t have to pick between a great extension and a healthy bank balance. Here’s what actually helps.
- Keep the shape simple. Square and rectangular footprints cost less than lots of corners and angles.
- Stay close to existing plumbing. Putting your new bathroom or kitchen near the old one saves real money.
- Decide early. Changing your mind mid-build is the most expensive thing you can do. Variations add up quickly.
- Be smart about finishes. Splurge where you’ll notice every day (the kitchen benchtop, say) and save elsewhere.
- Get several itemised quotes. Compare apples with apples, not just the bottom line.
- Think about orientation. Good natural light and cross-breezes cut power bills for years.
- Don’t skimp on the foundations or waterproofing. Cheap now, expensive later. Always.
Frequently Asked Questions
How much does a house extension cost in Wollongong per square metre?
Typically $2,500 to $5,000 per square metre for a single-storey extension with standard finishes. High-end finishes or difficult sites can go beyond $6,000.
Is it cheaper to extend or to move?
Often, extending is cheaper once you count stamp duty, agent fees and moving costs. But it depends on your property’s value and how much work is needed. It’s worth running both sets of numbers.
Do I need council approval for an extension in Wollongong?
Usually yes, either a development application or a complying development certificate through a certifier. Some very small works may be exempt. Check with Wollongong City Council or a qualified professional before you start.
How much extra should I budget for surprises?
Aim for 10 to 15 per cent on top of your quote. Older homes may need more.
Is a second-storey addition worth it?
If your block is small and you want to keep your backyard, yes, it can be. Just expect a bigger total outlay, typically $250,000 to $600,000.
Can I live at home during the build?
Often you can, especially with a rear extension. But expect noise, dust and no kitchen for a while. If you’re gutting the main living areas, renting nearby might be saner.
So, What Should You Do Next?
If I could leave you with just three things, they’d be these.
First, set a realistic budget that includes fees, approvals and a buffer. Second, get itemised quotes so you know what you’re really comparing. Third, talk to a local builder early, before you fall in love with a design that your block can’t handle.
At Modern View Constructions Pty Ltd, we love helping Wollongong families make their homes work better. No pressure, no jargon. Just honest advice about what your project might cost and how to get it done well.
Ready to find out what your extension could cost? Get in touch with Modern View Constructions today for a free, no-obligation chat and quote. Your future, less-elbowy kitchen is waiting.