HOW MUCH DOES A SECOND STOREY ADDITION COST IN 2025?
Thinking about adding a second storey to your home? How exciting! Going up is one of the most transformative moves you can make - breathing new life into a tired old house with more space, more light, and a whole lot more wow. ✨
But before you start planning that dreamy parents’ retreat upstairs with the walk-in robe you’ve been pinning for years, let’s talk about what it really costs to ‘pop the top’ in 2025, what drives those numbers, and whether it’s the right move for your home.
Here’s what we’ll LOOK AT:
Bon’s Brother’s Cottage
WHY MORE AUSSIES ARE BUILDING UP
Single-storey extensions are great, but they’re not always the smartest move for every home. Going up can unlock benefits that building out simply can’t match.
Save your yard: You get more living space without losing the lawn or that future pool site.
Maximise your space: Ideal for tight urban blocks where there’s no room to sprawl out.
Better views & privacy: Elevated living can give you privacy and perhaps treetop or city glimpses.
Boost your property value: A well-executed second storey can add serious value to your home.
Stay where you love: No need to move just because your family’s outgrown the floorplan.
But, of course, all that magic comes at a cost!
Bon’s Brother’s Inner City Cottage - Before
Bon’s Brother’s Inner City Cottage - After
HOW MUCH WILL A SECOND STOREY ADDITION COST?
There’s no one-size-fits-all price tag for a second-storey addition, but here’s a general guide to help set realistic expectations, based on our current industry intel.
| Project Type | Cost per m² (approx.) | Example Total* |
|---|---|---|
| Basic / modest build | $1,800 – $3,500/m² | $110,000 – $300,000 |
| Mid-range build | $3,500 – $5,800/m² | $250,000 – $500,000 |
| Premium / complex build | $6,000 – $15,000+/m² | $500,000 – $1.5m+ |
*Based on additions of roughly 60–100m², including typical structural, material and labour costs.
These figures are a starting point - your actual costs will depend on your home’s structure, design complexity, access, finishes and all those sneaky extras no one likes to talk about.
Deb McNee
WHY DO COSTS VARY SO MUCH?
Second-storey additions are never cookie-cutter. Here’s what really moves the budget needle:
1. Structural & Foundation Work
Adding a floor means adding weight. If your existing structure can’t support it, you’ll need reinforcements, underpinning or new footings, and that can be a big-ticket line item.
2. Roof Removal & Transitional Works
Unlike a ground floor extension, building up usually involves removing the roof and making the house liveable (and watertight) mid-build. That extra complexity means extra cost.
3. Design Complexity
Simple rooflines and boxy shapes are your budget’s best friend. Architectural details like balconies, raked ceilings, fancy window placement or curved details look incredible but will push the price up.
4. Plumbing, Services & Wet Areas
Bedrooms are relatively inexpensive in themselves. Bathrooms, ensuites or upstairs kitchens will see costs climb thanks to plumbing, waterproofing, and additional services required for these.
5. Fixtures & Finishes
Premium finishes like timber flooring, designer tapware and custom joinery bring the wow factor but also dollars. Clever product choices and shopping smarter with discounts will help keep things in check.
💳 Hot tip: Don’t forget to check out the Three Birds Dream Discount Card for savings every time you shop with our favourite suppliers.
6. Site Access & Logistics
Tight blocks, tricky terrain or limited access can mean cranes, extra scaffolding or additional labour. All of which can blow out costs quickly.
7. Approvals & Professional Fees
Architects, engineers, soil testing, council approvals and certifiers will all add to your budget. These are behind-the-scenes essentials that keep your project compliant and on track
8. Contingency & Surprises
There will be surprises. Always. Build in a 20% buffer for things you didn’t plan for but absolutely need to fix once they’re uncovered.
9. Living Arrangements During the Build
Some families live through it. Others move out. Either way, factor in what your life will look like during construction and budget accordingly.
10. Project Scale
Larger second storeys can be more cost-efficient per square metre because your fixed costs are spread out. Smaller additions can be surprisingly expensive.
Bec Berrell - Before
Bec Berrell - After
PROS AND CONS OF BUILDING UP
Before you commit, it’s smart to weigh up the good, the bad and the messy.
✅ Pros
More living space without losing your backyard
Better outlook, natural light and privacy
Often more cost-effective per m² than building out
Big potential to boost property value
Stay in your beloved neighbourhood
❌ Cons
Greater structural complexity (and cost)
More disruptive to your everyday life
Not all houses are suitable without serious reinforcement
Council height restrictions can be tricky
Longer build times and a higher risk of cost blowouts
REAL TALK: WHAT TO EXPECT THE TOTAL COST TO BE
For a mid-range second-storey addition of around 70–100 m² (think parents’ retreat, extra bedrooms and a bathroom), a realistic 2025 ballpark sits between $250,000 and $500,000.
Keep it simple, and you can land toward the lower end. Go luxe or face tricky site conditions, and that number can rise quickly.
Kylie Benson
The staircase at House 14
Top tips to keep your budget (and sanity) intact
Know your must-haves vs nice-to-haves - and stick to them! Adding to the scope will add to your budget.
Keep your design clean and simple - fewer rooflines and details = less cost.
Stack wet areas - align upstairs bathrooms above downstairs to save on plumbing.
Lock in fixed-price quotes - (where possible) and make sure you understand what’s not included.
Plan how you’ll live during the build - especially if your whole roof is coming off.
Build in a buffer - at least 10% (we prefer 20%). You’ll thank yourself later.
Work with experienced pros - second storey additions aren’t beginner builds.
Building up can be a game-changer for your home and lifestyle. It’s also a serious investment.
Whether you want to create the ultimate parents’ retreat, extra bedrooms for a growing family, or just squeeze more life out of a home you love, understanding the real costs upfront means fewer surprises down the track.
And if you’re already dreaming of those upstairs sunset views… this might just be the sign you’ve been waiting for.
✨ Psst! If you’re planning your own reno and want expert tips, cost-saving tricks and the confidence to tackle a project like this, you’ll love what we teach inside Three Birds Reno School. Your dream home is closer than you think.
