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Thinking about adding a second storey to your Perth home in 2025? You’re not alone. With real estate prices climbing and family needs evolving, more Perth homeowners are choosing to stay in the suburbs they love by building upward instead of relocating. A second-storey addition is a smart way to maximise space, improve your lifestyle, and increase property value without the hassle and hidden costs of buying a new home.
At Sertorio Homes, we specialise in custom second-storey home extensions designed to suit your lifestyle and budget. In this comprehensive guide, we’ll explain the average cost of a second-storey addition in Perth, the major cost factors, comparisons to other options like moving or rebuilding, and what’s included in a project with Sertorio Homes.
Average Cost of a Second-Storey Addition in Perth (2025)
As of 2025, a second-storey addition in Perth typically costs between $350,000 and $600,000, depending on your home’s existing structure, the level of design complexity, and your chosen finishes. Here’s a general cost breakdown:
| Project Type | Estimated Cost (AUD) |
|---|---|
| Partial addition (e.g. 1–2 rooms, ensuite) | $380,000 – $400,000 |
| Full second storey (3–4 rooms + bathroom) | $500,000 – $600,000 |
| Premium or architectural build | $600,000+ |
TIP: Costs can be reduced if plumbing and services (e.g., bathrooms) align with the existing ground floor layout. This saves time, materials, and labour.
What Affects the Cost of Building a Second Storey?
Several key factors influence the cost of a second-storey home addition:
1. Design Complexity
Simple box-style layouts are more cost-effective. If your design includes custom rooflines, balconies, voids, or architectural features, the cost increases significantly.
2. Site Access
Tight access for cranes or scaffolding can increase labour and extend the timeline, which adds to the overall cost. Homes on narrow blocks or in heritage areas often face access challenges.
3. Structural Engineering
Older homes may require underpinning or reinforcement, especially those built on limestone foundations. In some cases, chemical injection or steel beams may be necessary.
4. Fixtures and Finishes
Finishes are one of the biggest variables. Standard inclusions may include basic flooring, cabinetry, and fixtures. Upgrades to timber floors, stone benchtops, or high-end bathroom fittings can add tens of thousands to the final cost.
5. Living Arrangements
With Sertorio Homes, most clients stay in their home throughout the construction process. This is a huge cost-saving compared to renting elsewhere for 6–12 months.
What’s Included in a Second-Storey Addition by Sertorio Homes?
When you choose Sertorio Homes, you’re choosing experience, quality, and transparency. Every second-storey addition project includes:
Full architectural design and 3D rendering
Council approvals and permit applications
Fixed-price contract with no vague allowances
Construction, site management, and clean-up
Seamless integration with your existing home structure
Optional upgrades: ensuite, walk-in robes (WIR), balconies, home office space
We don’t just build — we guide you through the entire process with expert advice, realistic budgeting, and clear communication.
Second-Storey Addition vs Moving House or Rebuilding
Adding a second storey isn’t just about space — it’s also about financial strategy. Here’s how it compares:
| Option | Estimated Total Cost |
|---|---|
| Add second storey | $350,000–$600,000 |
| Sell and buy new home | $80,000–$150,000+ in fees, stamp duty, moving, renovations |
| Knockdown and rebuild | $500,000–$800,000+ |
Building up is often the most cost-effective and emotionally satisfying option — especially if you love your location, have friendly neighbours, or live near schools, parks, or work.
FAQs About Second-Storey Additions in Perth
How long does a second-storey addition take to complete?
On average, 10–12 months, depending on weather, access, and design complexity.
Can I live in my home during the build?
Yes. Sertorio Homes specialises in live-in renovations that minimise disruption and maintain safety.
Do you offer fixed-price contracts?
Absolutely. After design and scope finalisation, we provide a transparent, fixed-price contract so you know exactly what you’re paying for.
Why Choose Sertorio Homes for Your Second-Storey Addition in Perth?
We’ve been building beautiful, high-quality home extensions across Perth for over 40 years. Our reputation is built on exceptional craftsmanship, client-first service, and honest communication. We tailor every design to suit your family’s needs, your budget, and your vision.
If you’re ready to add space, style, and value to your home, we’re here to help.
Get a Personalised Quote Today
Ready to explore your options? Book a free consultation with our design team or call us on 08 9244 1993. We’ll assess your home, listen to your goals, and show you what’s possible — with no pressure and no obligation.
Build smarter. Build upward. Build with Sertorio Homes.