Single Storey to Double Storey Conversion: What to Know

A single storey to double storey conversion adds a full second level to your existing home, allowing you to double your living space without giving up your block or your neighbourhood. For families across the Sutherland Shire and Georges River area who love where they live but have outgrown their house, this type of project delivers the extra bedrooms, bathrooms, and living areas you need while keeping everything you already value about your location.

Dura Group Building & Renovations has completed second storey conversions on fibro cottages, brick homes, and weatherboard houses throughout suburbs like Engadine, Jannali, and Peakhurst. Below, we walk through what is involved so you can plan with confidence.

What is involved in converting a single storey home to double storey?

The process involves removing your existing roof, reinforcing or replacing the structural frame, building new walls and a floor platform for the upper level, then constructing a new roof over the top. A temporary weather protection system covers your home during the open-roof phase to protect interiors from rain.

Key stages include:

• Structural engineering assessment of foundations, walls, and load paths
• Architectural design and council approval (Development Application in most cases)
• Roof removal and installation of temporary weatherproofing
• Construction of the upper floor frame, walls, and new roof
• Internal fit-out including staircase, electrical, plumbing, and finishes
• Final inspections and occupation certificate

If you are considering alternatives, our guide to second storey extensions covers partial upper additions that may suit smaller budgets.

Can existing foundations support a second level?

Not always. A structural engineer must assess whether your current footings can carry the additional load of a full upper storey. Older homes built on strip footings or shallow piers often need reinforcement. Fibro cottages common across Engadine, Heathcote, and Gymea were typically designed for single storey loads only.

When foundations are inadequate, underpinning is required. This involves excavating beside existing footings and pouring new concrete to deepen and widen them. In some cases, new pad footings or piles are installed at key load-bearing points.

The cost of foundation work varies based on soil conditions and the extent of reinforcement needed. Sandy soils near the Georges River behave differently to clay soils further inland, so site-specific engineering is always required. For a broader look at project budgets, read about home extension costs and factors that influence pricing.

Do you need council approval for a second storey conversion?

Yes. A Development Application (DA) is almost always required because adding height triggers assessment for overshadowing, privacy, bulk, and scale. Unlike minor ground floor additions that may qualify for a Complying Development Certificate (CDC), second storey conversions change the building envelope in ways that affect neighbours.

Sutherland Shire Council and Georges River Council both assess:

• Shadow diagrams showing impact on adjoining properties at 9am, 12pm, and 3pm on 21 June
• Privacy measures such as window placement, sill heights, and screening
• Compliance with floor space ratio (FSR) and height of building controls
• Setback requirements for the upper level

Understanding DA approval process helps you plan realistic timelines. DA processing typically adds 8 to 16 weeks before construction can begin.

How long does a second storey conversion take?

Most full second storey conversions take between 6 and 12 months from construction start to completion. The timeline depends on the size of the addition, complexity of structural work, and whether you are also renovating the ground floor.

A typical breakdown looks like this:

• Design and DA approval: 3 to 5 months
• Site preparation and foundation work: 2 to 4 weeks
• Roof removal and upper level frame: 4 to 6 weeks
• Lock-up stage (roof on, windows in): 6 to 8 weeks
• Internal fit-out and finishing: 8 to 14 weeks

Dura Group prepares all materials and trades before starting on site, which reduces delays during construction. Weather is the main variable during the open-roof phase, though our temporary protection systems keep the interior dry.

Can you live in the home during a second storey conversion?

It depends on the scope of work, but most families choose to move out during the roof removal and framing phases. Once the new roof is on and the home is weatherproof again (typically 6 to 10 weeks into construction), some homeowners move back in while upper level fit-out continues.

Factors that affect liveability during construction include:

• Noise and dust from demolition and framing
• Temporary disconnection of services during re-routing
• Access restrictions while scaffolding is erected
• Safety considerations if young children are in the home

We discuss this early in the planning process so you can arrange temporary accommodation if needed. Some of our clients in Hurstville and Peakhurst have stayed with nearby family during the open-roof stage, which keeps the disruption manageable.

Where should the staircase go?

Staircase placement is one of the most important design decisions because it determines how much ground floor space you lose and how the upper level flows. A standard staircase needs roughly 3.5 to 4 square metres of floor area on each level.

Common options include:

• Central hallway placement, which minimises disruption to existing rooms
• Along an external wall, which preserves open-plan living areas
• Within an existing room that will be reconfigured (such as a study or store room)

Your architect will test multiple staircase positions during design to find the layout that works best with your existing floor plan. If a house extensions is also part of the project, the staircase can be positioned within the new addition rather than taking space from existing rooms.

How does the cost compare to a knockdown rebuild?

A second storey conversion typically costs 30 to 50 percent less than demolishing and rebuilding the entire home. You retain existing foundations (with reinforcement), ground floor structure, plumbing connections, and often the ground floor fit-out.

Cost drivers for a second storey conversion include:

• Foundation reinforcement or underpinning requirements
• Size of the upper level (number of rooms and bathrooms)
• Whether the ground floor is also being renovated
• Site access for crane and scaffold
• Engineering complexity of removing the existing roof

A knockdown rebuild makes more sense when the existing structure has serious issues like termite damage, major cracking, or non-compliant setbacks. For more on this decision, read our comparison of whether it is cheaper to renovate or rebuild. You can also review building costs in Sydney and cost per square metre rates to understand how budgets are structured.

Why do families choose a second storey conversion?

Most families choose this option because they love their block, their street, and their local area but simply need more space. Selling up and buying a larger home in the same suburb often costs more than adding a level, especially in established areas where land values are high.

A second storey conversion suits you if:

• Your children are in local schools and you want to stay in the catchment
• You have a backyard you do not want to sacrifice to a ground floor extension
• Your block is too small for a knockdown rebuild with compliant setbacks
• You want to retain established gardens, trees, or outdoor living areas

Across the Sutherland Shire, fibro cottages on generous blocks are ideal candidates. Suburbs like Engadine, Gymea, Jannali, and Kirrawee have hundreds of single storey homes on 600 to 800 square metre lots where a second storey fits comfortably within height and FSR controls. Homes backing onto bushland reserves or with district views gain the most from an upper level, both in liveability and property value.

What temporary weather protection is used during construction?

Industrial-grade scaffold shrink wrap or temporary roofing panels are installed before the existing roof is removed, creating a waterproof barrier over the open structure. This protects ceilings, floors, and belongings from rain damage during the framing phase.

The protection remains in place until the new roof sheeting and sarking are installed. Dura Group schedules roof removal during dry weather windows wherever possible, though the temporary system means construction is not weather-dependent.

Ready to start your second storey conversion?

If you are considering adding a second level to your home in the Sutherland Shire or Georges River area, contact Dura Group for a site assessment and obligation-free discussion about what is possible on your block. With 25 years of experience and fixed lump sum pricing, we make the building process clear from start to finish. Explore our full range of home extensions and additions or connect with our team of Engadine home builders, builders in Peakhurst, builders in Hurstville, or builders in Gymea.