How much does a Second Storey Addition cost?
Quick glance Summary
- Typical Cost Range (2025/2026): $380,000 to $650,000+
- Lower Range: Covers a second storey with one or two bedrooms and a bathroom and custom staircase.
- Upper Range: Includes high-end finishes, complex designs, a larger footprint, or ground floor extensions and renovations in addition to the second storey.
- What Affects Price: Design complexity, size, ceiling height, staircase type, materials, fixtures, fittings, tiling height, and number of wet areas.
Factors affecting Second Storey costs
Second Storey additions are a great way to add living space and extra rooms to your home, without losing yard space or much of your existing floorplan.
At Amerex, second storey additions generally range from $380,000 to $650,000+, depending on the size, layout, design specifications, and whether additional ground floor extensions and renovations are required too.
Adding a master bedroom and ensuite upstairs may fall closer to the lower end, while larger projects with multiple bedrooms, bathrooms, a living area and a balcony, or incorporating a ground floor extension will trend higher.
This range reflects current 2025/2026 pricing and ensures you’re budgeting realistically from the start.
How we build sustainability and longevity into your Second Storey Addition
Amerex is leading the way in Perth by including sustainable, energy-efficient features as standard in every second storey addition, not as added extras or hidden exclusions.
Our second storey additions include these added sustainability measures as standard in every project:
- Premium Insulation: Internal and external walls are insulated to reduce noise transfer and maintain even temperatures year-round. Many builders only provide insulation for external walls. We insulate every wall to improve comfort and liveability. Trust us, there is a big difference.
- Thermal Efficiency: Roof spaces include an Anticon blanket to reduce condensation and improve acoustic comfort. This will reduce potential future issues with mould.
- Lightweight Concrete Flooring: Provides a solid feel, excellent noise reduction, and superior thermal performance compared to chipboard used by other builders.
- LED Lighting and Electrical Safety Upgrades: Enjoy bright, energy-efficient LED lighting and added peace of mind with safety switches (RCDs) that instantly cut power if something goes wrong.
- Sustainable Wall Cladding: We use high-quality EPS cladding -not thin blueboard commonly used in the industry – for better insulation and long-term durability.
These features are included as standard, setting Amerex apart as a builder focused on quality, comfort and sustainability. Further info on our sustainable approach to be building can be found here.
Second Storey Addition Costs and Design factors
A second storey addition will involve ground floor modifications to create space for the new staircase. This is one of the first thing and most important design decisions to make. Our experienced designer will walk you thru your alternatives during the design stage.
What rooms will you have upstairs?
Deciding what rooms you need upstairs will have the biggest impact on cost — for example, a master bedroom with ensuite, children’s bedrooms with a shared bathroom, separate WC or activity area. These details are worked through early with your designer and builder.
Can you build a partial second storey addition?
This sounds a little strange, but the answer is yes! This happens when a home has an existing upper floor and requires a new addition to extend it even further.
Lightweight Construction: Efficient and Cost Effective
Unlike a Ground Floor Home Extension, a second storey addition does not normally require any foundations or concrete slab to be poured. Our second storey additions are built using a lightweight timber frame system engineered for strength and performance.
Amerex adds value and quality to your second storey by building with premium materials and sustainable methods for improved energy efficiency — a feature not commonly offered by other builders. Read more about our sustainability initiatives here.
Cladding, Windows & Ceilings
For your new level, we recommend EPS cladding for durability and insulation performance. It’s a better choice than standard blueboard (commonly used by most builders) which can crack over time.
We also provide a window consultation to help you select energy-efficient options such as Low-E or double-glazed glass, improving comfort and thermal performance throughout the year.
Ceiling heights can influence both aesthetics and cost — our experienced designer can help you maximise the sense of space while staying within council height limits.
How do I get an accurate quote for my Second Storey Addition?
With more than 30 years of experience, Amerex specialises in second storey additions that combine quality craftsmanship with sustainable design.
Current pricing starts from $380k increasing to $500k+ when combined with ground floor extensions, depending on scope, finishes and the number of rooms or wet areas.
Each project is unique, and we’ll tailor your quote to suit your design, budget and lifestyle goals. If you already have plans, we can provide a quote (note that a fee for this service applies).
Why Choose Amerex for your Second Storey Addition?
- Award-Winning Expertise: Six-time HIA WA Professional Small Builder/Renovator of the Year and award cabinet boasting 70+ awards.
- Here to Stay: With over 30 years of experience designing and building second storey additions, we’re the safe, proven and reliable choice.
- Comprehensive Services: From initial design to final handover, we manage every aspect of your project to make it easy for you.
- Sustainability as Standard: Every project includes premium insulation, thermal efficiency upgrades and sustainable materials — built to perform, not just to pass minimum standards.
- Peace of Mind, Guaranteed: We offer a full 12-month maintenance warranty—four times longer than the industry standard.
Second Storey Design service
If you haven’t started the design stage, get in touch and we can manage the entire process from design, planning, construction thru to handover and maintenance.
Contact the Amerex team and let’s discuss your project ideas.