Thinking about adding more room without giving up your backyard? For many Sydney families, building up is the smarter choice. A first floor or second storey addition not only creates the space you need while keeping you in the neighbourhood you love, it’s also an opportunity to reimagine your entire home.

Homeowners use second storey additions in all kinds of ways!
Including, moving bedrooms and bathrooms upstairs to free up the ground floor, opening up living areas for a more connected lifestyle, and upgrading kitchens and bathrooms as part of one cohesive design.
Building vertically also means preserving precious outdoor space, while unlocking elevated views and adding long-term value to the property.”

The result is a home that feels dramatically transformed, and a property that’s future-proofed for decades.

But before you start planning upstairs bedrooms or elevated views, there’s one big question:

Will your existing foundation actually support the extra weight of a second storey?

The Short Answer: Often Yes — But It Depends

Many homes can handle the addition of a second storey, but every site is different. The age of your home, the type of slab or subfloor, soil conditions, and past renovations all influence whether your foundation can take the load.

That’s why the first step isn’t drawing up plans, it’s understanding the bones of your home.

How Builders Assess Your Foundation

When you engage a specialist builder, the process usually includes:

• Condition checks of your existing slab or subfloor
• Structural engineering to design new steel beams, tie-ins, and bracing
• Service integration so plumbing, drainage, and electrical work seamlessly between floors
• Waterproofing and insulation strategies to protect performance long-term

This stage sets the tone for the entire build. It’s not about “can we add a second storey?” but “how do we do it safely, seamlessly, and with foresight?”

Why Planning Matters More Than Possibility

Adding a floor isn’t a cosmetic upgrade. It’s a major structural change. Poor planning can lead to cracks, leaks, or worse, but done well, a second storey feels like it’s always belonged.

Specialist builders focus on more than just structure:

• They design for cohesion, so the extension doesn’t look tacked on.
• They ensure transitions between old and new are seamless.
• They plan for long-term durability, not just the build itself.

Approvals: DA or CDC?

In Sydney, second storey additions need approval. Depending on your block and design, you may be able to fast-track with a Complying Development Certificate (CDC), or you may need a full Development Application (DA).

An experienced builder will guide you through:

• Zoning checks and site analysis
• Pre-lodgement advice to speed things up
• All drawings, reports, and compliance documents
• Coordination with certifiers and consultants

This is where experience across different councils really pays off.

Already Have Plans?

If you’ve already engaged an architect or designer, you don’t need to start over. A builder with second-storey expertise can review your plans, check structural viability, and work alongside your consultants to bring the design to life.

So, Can Your Foundation Support a Second Storey?

The answer is rarely black and white. For some homes, it’s a straightforward yes. For others, additional engineering or reinforcement is required. Either way, with the right planning and expertise, building up is possible for many Sydney homes.

The important part is having it assessed early, before you fall in love with plans that your foundation can’t support.

The Takeaway

A second storey is one of the smartest ways to gain space, add value, and future-proof your home, but it all starts with the foundation.
With the right due diligence, structural engineering, and design-led approach, your home can grow upwards with confidence.

If you’re considering a second storey addition in Sydney, talk to Phase Projects.
We’ll assess your foundations, guide you through approvals, and deliver a result that feels like it’s always belonged.

Get in touch

7 FAQs About Second Storey Additions in Sydney

1. Can my existing foundation support a second storey?
Often yes, but it depends on the age of the home, soil conditions, and the strength of the slab or subfloor. A structural engineer will assess this before design begins.

2. Do I need council approval to add a second storey?
Yes. Most projects require either a Development Application (DA) or may qualify for a Complying Development Certificate (CDC). Your builder will guide you through the right path.

3. How much does it cost to build a second storey in Sydney?
Costs vary widely depending on the design, finishes, and structural requirements. A detailed site inspection and engineering report are needed to provide an accurate proposal.

4. How long does a second storey addition take?
Most projects take 8–12 months, depending on approvals, complexity, and weather.

5. Will the new level blend in with my existing home?
With thoughtful design and detailing, yes. A specialist builder ensures the addition feels original, not “tacked on.”

6. What upgrades are common with second storey builds?
Many homeowners take the opportunity to reconfigure the ground floor, upgrade kitchens and bathrooms, and improve overall flow and finishes.

7. Is building up better than extending out?
For many Sydney blocks, yes. Building vertically preserves outdoor space, maximises land value, and often delivers better views.