If you’re considering a second storey addition in Perth, you’re not alone. With block sizes tightening and lifestyle needs evolving, “going up” remains one of the most effective ways to add space and value—without sacrificing the backyard.
But naturally, the first question on most homeowners’ minds is: How much does a second storey addition cost in 2025?
And the honest answer? It depends. Here’s why.
The Real Cost of a Second Storey in 2025
For a quality, architecturally considered second storey addition in Perth, you can expect to invest somewhere between:
💰 $300,000 to over $700,000+
At Addstyle, our second storey projects typically range between $350,000 and $600,000, depending on the size, layout and finishes.
That range may sound broad—but it’s entirely dependent on the details. And that’s something we believe homeowners deserve transparency from the start.
Why “Price Per Square Metre” Is Misleading—Especially for Second Storeys
Some builders will start by citing a square metre rate to make the quoting process sound simple—but for a second storey addition, it’s rarely accurate and often misleading.
Not all square metres are created equal.
There are too many variables at play for a square metre rate to be meaningful.
Let’s start with the big ones:
- Access: Can scaffolding be erected easily? Is the block sloping or restricted? These factors alone can shift the base cost of construction.
- Ceiling Heights: Are we matching high ceilings below, or lowering them upstairs?
- Material Selection: Are we finishing in weatherboard, render, face brick, or something else? Is the roof tiled or tin? Are the windows aluminium or timber?
- Structural Integration: Is the staircase placement straightforward, or does it require reworking part of the existing ground-floor layout?
- Floor System: Will the addition have a solid, sound-insulated aerated concrete floor system—or cheap compressed sheeting?
Now add the finer – but no less important – details:
- Full-height tiling or skirting tile only?
- Stone benchtops or laminate?
- Timber skirtings, cornices and architraves to match the original home—or MDF, cove cornice, and metal doorframes to save cost?
- Open-tread timber and glass staircase, or a basic enclosed stair with carpet?
The difference in cost and outcome, is significant.
Yet a square metre rate glosses over all of that. It assumes every square metre is built and finished the same way. But when you’re creating an upper level that needs to integrate seamlessly with the floor below, that assumption falls apart quickly.
This is why many builders present appealing “from” prices up front – and leave you to discover the compromises later.
At Addstyle, we prefer to have the honest conversation from day one. Because when you’re building on top of your most valuable asset, you want to get it right the first time. And that starts with understanding the full picture – not just the price per square metre.
Key Factors That Influence the Cost
1. Size, Scale, and Ceiling Heights
Well-designed additions take into account:
- Room proportions that will realistically accommodate your furniture and are in proportion to the existing ground floor rooms
- Ceiling heights that are appropriate to the home (particularly important if the ground floor has high or decorative ceilings); and
- An overall footprint that sits in proportion to the original structure, both internally and externally
These architectural decisions aren’t just visual—they influence your experience of the space every day.
2. Staircases: Structure and Statement
Every second storey addition requires a staircase, and the style chosen can greatly affect the cost:
- Open tread timber on steel spine with glass balustrade = premium
- Enclosed MDF with painted timber balustrade = cost-effective
It’s not just a functional component, it’s often the architectural feature that links old and new.
3. Fixtures, Finishes, and Functionality
Details matter – especially in a second storey addition where you might be introducing bathrooms, built-in storage, or even a kitchenette or study nook.
Some of the most common upgrade variables include:
- Full-height tiling vs. skirting tile
- Natural stone benchtops
- Decorative mouldings
- Timber or aluminum windows – and whether they match the floor below
- Custom joinery vs. off-the-shelf wardrobes or vanities
- Lift Shafts and Lifts
- Laundry Chutes
- Wet Bars/Kitchenettes.
These aren’t indulgences – they’re part of creating a cohesive, consistent, quality home.
We Don’t Use Compressed Timber Flooring—and Here’s Why
At Addstyle, we build second storeys to the same structural integrity as the ground floor. That means using an aerated concrete floor system, not compressed timber or fibre cement sheeting.
The benefits are significant:
- Superior sound insulation
- Better thermal performance
- A solid, concrete-like feel underfoot
- Greater longevity and comfort overall
Compressed sheet flooring is often used by builders to keep costs down, but it’s a shortcut we strongly advise against.
The Importance of Material Consistency
It’s not uncommon to see second storeys built with aluminium joinery while the ground floor features traditional timber frames. It’s less expensive, but aesthetically disjointed – and potentially value-reducing.
We always advise clients on how to maintain visual harmony between floors:
- Matching window styles, skirtings, architraves, and cornices
- Choosing materials that suit the home’s architectural style
- Ensuring the upper storey feels cohesive, not bolted on
These are conversations we prioritise early—because they matter.
Case Study #1: Character Home in Nedlands
- Original age of home: 1990’s
- Second Storey Scope: Parents’ retreat, ensuite, His & Hers dressing rooms, sitting area, study, and staircase with grand void
- Inclusions: Painted face-brick in replicated style to existing, custom shaker joinery and Caesarstone cabinetry, timber windows and doors, matched period features including replicated lead-light windows
- Outcome: A fully integrated second storey addition that preserved the home’s 1930s character while delivering contemporary comfort and functionality
- READ MORE ABOUT THIS PROJECT
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Character Style Second Storey Addition in Nedlands
Case Study #2: Hamptons Style Makeover in Mount Claremont
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Original age of home: Circa 1980s
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Second Storey Scope:
Main bedroom suite with ensuite and dressing room, three additional bedrooms, bathroom, separate WC, activity room, linen, and stairwell with double-height void. -
Inclusions: Weatherboard cladding, engineered timber flooring, ‘Lambs Tongue’ skirtings, shaker-style cabinetry, Caesarstone benchtops (Empira White & Organic White), feature staircase with glass balustrade and powder-coated gold fixings, aluminium joinery (colour-matched to timber below), Colorbond roofing in Surfmist.
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Outcome:A substantial second storey addition delivering Hamptons-inspired elegance and scale, while remaining sympathetic to the 1980s-built home. The new level adds balance, flow, and family functionality—designed for long-term liveability with timeless appeal.
- READ MORE ABOUT THIS PROJECT
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Hamptons Style Second Storey Addition in Mount Claremont
Are Second Storey Additions Worth It?
Done well, absolutely. A second storey can:
- Unlock valuable living space
- Preserve your outdoor area
- Add long-term value to your property
- Enhance your home’s design, flow, and flexibility
- Future-proof your home for growing or changing family needs
The key is in the planning and the execution.
Start With the Right Conversation
At Addstyle, we don’t offer generic inclusions or square metre rates. We don’t gloss over the details to win a job. What we do is listen, design thoughtfully, and deliver quality that lasts.
Our process includes:
- A complimentary in-home consultation
- Tailored design concepts presented in 3D
- A fully documented fixed-price contract
- Seamless project management—from approvals to handover
📍 If you’re ready to take your home to the next level—literally and beautifully—we’d love to talk.
