Single-Storey vs Double-Storey Home Extensions: A Comprehensive Comparison

Carefully weighing single vs double-storey extension pros, cons, costs, and other factors is vital for your investment decision. This guide provides a detailed analysis to choose the best option for your property confidently.

Single-Storey Extension or Second-Storey Addition: A Detailed Comparison

Adding extra space to your home in Sydney is an exciting project but also a significant investment. One of the first big decisions is whether to build out with a single-storey extension or build up by adding another level. Both options have pros and cons to weigh up.

This guide will outline the key differences between single and double-storey extensions. We'll compare factors like cost, construction time, design flexibility, planning regulations and future value. You'll get a detailed analysis to help inform your choice between expanding your footprint versus going upwards.

By the end, you'll have the information you need to determine whether a single-storey or upstairs extension is the right choice for your Sydney home, lifestyle and budget. Let's weigh up the pros, cons, costs and considerations.

Weighing Up the Key Differences

When deciding whether to build a single or double-storey extension in Sydney, there are several key factors to consider:


  • Single-storey additions are generally less expensive per square metre. Materials and labour are lower without the need for stairs, reinforcements etc. But double-storey allows you to maximise available land.

Design and Layout

  • Single-storey extensions offer more design flexibility in terms of layouts and ceiling height. Double-storey can have restricted headroom and room shapes upstairs.

Construction Timeline

  • Single-storey additions are typically faster to build with less disruption to your home. Multi-level extensions require more complex structural work.

Planning Approval

  • Single-storey extensions have a higher approval rate if they are within council regulations. Double-storey additions have more criteria to satisfy around neighbour impact.

Future Expansion

  • Adding a second storey later is very difficult. Single-storey leaves future potential to build up.

Here is a summary comparison:

Cost per m2LowerHigher
Design FlexibilityMore optionsRestricted by stairs
Build TimeQuickerLonger
Council ApprovalHigher chanceMore considerations
Future ExpansionEasierVery difficult

By weighing up these fundamental differences, you can determine whether a single or double-storey extension better suits your property, budget and lifestyle. Next we'll dive into a detailed cost comparison.

Cost Comparison

The cost is one of the most significant factors when deciding between a single and double-storey extension. Adding a second level generally costs more per square metre.

Some critical reasons for the higher cost:

Materials - Extra concrete, steel, wood and roofing are needed to support a second level. This adds significantly to material costs.

Stairs - A staircase will be required, either open or closed. This also uses up floorspace in the addition.

Labour - More specialised labour is needed for the extensive structural work and finishing of a second storey. This increases labour costs.

Excavation - Extra soil may need to be dug out and removed for a raised foundation, depending on the site.

Windows - More windows are usually added upstairs, which adds expense over a single level.

Complex systems - Plumbing, electrical and HVAC systems are more complicated over two levels.

According to industry guides, a second-storey addition generally costs 10-25% more per square metre compared to a single-storey.

Of course, exact costs depend on factors like design, finishes, site conditions and more. Get quotes from builders to compare pricing. While double-storey costs more overall, the upside is maximising your available land by building up.

Design Possibilities and Constraints

When designing a home extension, single and double-storey additions each have their own possibilities and constraints in terms of layouts, dimensions and features.


  • More flexible room shapes and sizes - can optimise layout without stairs or upper-floor supports
  • Higher ceilings possible - up to 3m for an open, spacious feel
  • Easier to maximise natural light - skylights, windows and doors on multiple sides
  • Choices for split-level rooms, sunken areas, open-plan
  • Rear access is possible for a flat, single-story design


  • Footprint limited by the need for stairs - eats into floorspace
  • Lower ceiling height upstairs - around 2.4m is typical
  • Lighting and ventilation can be issue - windows only on exterior walls
  • Room shapes restricted by upper-floor footprint
  • Access only from the ground floor entry

When going upstairs, minimum dimensions need to be allowed for hallways and stairs. This does limit layout options compared to single-storey. And lower second-storey ceilings can make rooms feel cramped.

But two levels allow you to maximise the available footprint for a bigger total floor area. Just be aware of the lighting, ventilation and shape constraints when designing rooms upstairs.

Getting the layout right for your needs and tastes is critical. Explore concept designs and 3D modelling with architects to assess the options.

Build Time and Disruption

The construction process differs significantly between single and double-storey home extensions. Build time, access issues, and disruption should be factored in when deciding on an addition.


  • Faster build time - can be completed in 3-6 months
  • Potential to remain living in the home during works
  • Less noise impact on your home life
  • Easier vehicle access to the site


  • Longer build - typically 6-12 months
  • More likely to require moving out temporarily
  • More significant noise disruption over a longer period
  • Access can be restricted during structural works
  • For single-storey extensions, the ability to remain in your home is a major benefit, reducing costs and disruption. The quicker build also gets your new addition liveable sooner.

With a second-storey build, the extended structural work makes it harder to stay on-site during construction. The longer build time also impacts liveability. Carefully discuss timeframes with your builder. And factor in contingency for potential delays, especially with double-storey projects.

The right planning minimises disruption. But single-storey extensions have a clear advantage when it comes to construction impacts.

Gaining Approval

When adding an extension in Sydney, gaining council approval is key. Both single and double-storey additions have planning regulations to satisfy, but there are some differences.


  • High approval rates if within rules for height, setbacks, site coverage and height
  • Easier to demonstrate minimal impact on the streetscape and neighbours
  • Can maximise allowable footprint under council rules


  • Must comply with floor space ratio (FSR) and overall height limits
  • More chance of objections around privacy, overshadowing and views
  • Needs sympathy with neighbourhood streetscape and character
  • Must meet balcony/deck setback rules on upper levels

For a single-storey extension, approval mainly depends on complying with site coverage and setback allowances. Provided you stay within the rules, approval is very likely.

Double-storey additions have more potential impacts that councils will assess, like overshadowing, overlooking of neighbours and visual bulk. The approval criteria are more complex.

Seek professional advice from architects and planners when designing your plans. They can tailor designs to maximise your chances of approval.

Future-Proofing Your Investment

When assessing single-storey versus double-storey extensions, it's wise to consider future needs too. Will the additional space still work as your family grows? What value might it add to your property over time?


  • This leaves open the possibility of building upwards later for more space
  • Provides a value-adding opportunity by boosting footprint for future second-storey
  • Easy to repurpose extra bedrooms back to living space


  • Very difficult to expand further once two levels are built out
  • Adding more levels would require major structural upgrades
  • Hard to alter upstairs layouts once built, which limits future flexibility

With a single-storey extension, you retain the option to add another level in future if needed. This can be a smart way to stage your expansion.

A double-storey addition pretty much maxes out your potential. Trying to add more floors down the track would be extremely difficult and expensive.

Carefully project your long-term needs. Leaving room to grow can be a savvy investment in your property's future value.

Single or Double? Weigh Up Your Options With Buildrite

Deciding between a single or double-storey home extension is a significant choice. It pays to carefully weigh up the differences in cost, design, build time, approvals and future flexibility.

While two levels allow you to maximise your footprint, the higher costs, restricted layouts and prolonged disruption are downsides. Single-storey additions offer faster construction, more design freedom and the potential to build upwards later.

To determine the best option, analyse your budget, lifestyle needs, site specifics and council regulations. Get professional advice from architects, builders and planners. Together you can create plans that make the most of your available space.

Adding a well-designed extension improves your living comfort today and boosts your property value into the future. We hope this guide has given you all the information to confidently choose between building out or upwards.

For a free, no-obligation consultation on a Sydney home extension, get in touch with our team at Buildrite. We're here to chat through your options, ideas and budget to start planning your ideal addition.

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