How much does a loft conversion or second storey addition cost in Australia

An average loft conversion or second-storey addition in Australia will cost anywhere from $200,000* to $450,000+*, depending on size, the quality of finishes, structural requirements, etc.

Skylights in a renovated house with a loft conversion.
ARTICLE Carol Watson  and Stephanie Matheson

Have you reached that stage where your existing home does not meet the needs of your growing family? Rather than endure the hassle of moving and the waste of money on stamp duty, why not use the space you’ve already got? Turn your loft into another room or simply add a second-storey.
An average loft conversion or second-storey addition in Australia will cost anywhere from $200,000* to $450,000+*, depending on size, the quality of finishes, structural requirements, etc.
Here is how you can make the most of your existing space, while keeping renovation costs down.

Where do I start?

The first step in your plan is to work out if your loft is suitable for conversion and can it be turned into a ‘habitable’ room. According to The Building Code of Australia, a ‘habitable’ room or space within a building must have sufficient height suitable for the intended function of that room or space. If your new loft space is to be used as a bedroom, then the minimum head height will need to be 2.4 metres in at least 60 per cent of the floor area once it’s built. When measuring the height, you will need to factor in space for new ceilings and floors.
Whilst you might be tempted to compromise on this head height, bear in mind that should you sell your house in the future, you will not be able to market this room as, say a bedroom, if it does not meet the required head height. Depending on location, there is a significant price difference between a three-bedroom and four-bedroom house. To get the maximum return on your renovation investment, you should adhere to this building code standard.
hand drawn architectural illustration of wooden attic, perspective view
If you find that your existing loft space will not provide enough room to justify the costs, then consider adding a second storey. In many ways, this presents a better opportunity to gain more living space than a loft conversion. There is scope to add more than one room and you won’t affect the size of the footprint of your existing building and the floor space-to-land ratio.
Loft conversions or second-storey additions typically require structural and/or foundation work, as the original house would not have been build to hold the weight of a second storey. In many cases, extra steel and/or timber beams will have to be installed to support a new second storey. Keeping the number of steel beams down – and using timber for strengthening where possible – will lower your building costs. In addition to the new steel or timber sub-structure, often the existing loft flooring needs to be underpinned and strengthened with the addition of extra floor joists. Your renovation specialist will get experts to properly design and plan this kind of structural and foundation work.
Weather-proofing during the construction of your second storey is one of the main concerns, as this requires the removal of the existing roof and the use of scaffolding for access. Full scaffolding that can be wrapped in plastic shrink wrap is a great option, as opposed to the conventional tarps that are not secure and often don’t provide sufficient protection from the elements. Shrink-wrapped scaffolding provides water-tightness and allows the builders to work in any weather, thus helping to avoid weather-related delays that can be costly both in terms of time and money.

Is my roof suitable for a conversion?

Generally speaking, the steeper the pitch of your roof, the more likely it is that your roof will be suitable for a conversion. Not having to alter the roof itself will keep your costs down, as you will only need to install skylights or dormer windows into the pitch of the roof to provide natural light. If you are changing your roofline or an existing roofing product, you will need to apply for approval from your local council. Your renovation specialist will give you guidance on these requirements.
Skylights of a house that has been renovated with a loft conversion

What type of window styles can I choose from?

Skylights or roof windows can be the most cost-effective way to let light into your new loft room. They can be fixed windows or opening windows and can come with fixed flyscreens and solar blockout. Another optional extra for these windows are rain sensors, so you can rest assured that your rooms are safe from water damage in the event of a sudden rain shower. Go for a standard skylight if you are wanting a basic option or get optional extras like opening and closing mechanisms for those with a little more budget. You will also need to pay installation costs.
bathroom in loft conversion with sky lights
The downside of skylights or roof windows is that they are flush with the roofline and so will not help create any more space.
Dormer windows, on the other hand, protrude from the sloping roof and create that precious extra headroom. They are a great option when you want to maximise the available loft space and meet the head height standards. If your budget allows, you can even consider installing French doors or sliding doors with a glass balustrade or small balcony. These solutions create the feeling of a more open space and let natural light flood in.

What are my staircase options?

Carpet-wrapped steps are the most cost-effective option when it comes to stairways. A set of straight stairs are easiest to build and install, and hence very affordable. Depending on your space and requirements, however, a set of turning stairs might be required. A simple option is to go for a set of carpet-covered stairs with several steps leading to a small platform and then turning 90 degrees. If you choose different materials, such as hardwood timber or glass for the steps, or add a balustrade, this will increase the cost. Floating steps or curved staircases – in the upper regions when it comes to price – add a bit of drama and visual impact. Floor-level lighting and art embedded into the steps add further to the wow factor.
Stairs are generally easy to build and install, however, carefully planning and positioning at the outset of your project is important to ensure you don’t lose precious space on your ground floor. As a rule of thumb, it’s likely that stairs will take up about half a small room. Where space is extremely tight you could consider a small spiral staircase keeping in mind though, that access can be an issue and items of furniture may have to be lifted in and out through the upstairs windows. Make sure you allow for installation costs.

What is involved in a roof conversion?

Not changing your roofline means that you are likely to be able to leave most of your roof untouched. You will simply need to tidy up and repair roofing where your windows will be inserted. However, any work done on a roof requires a scaffold or edge protection, which will add to the cost of your project. Also, it’s not uncommon for problems, such as old leaks and rot of roof beams to be uncovered during the build. Ensure you have a contingency budget of at least 15% planned in.
If your loft conversion is a more substantial project, you may have to replace some or all of the roofing. Costs for replacing or repairing a roof depend on the roofing material of your house, size and pitch of the roof and other factors.
loft conversion with custom staircase
Metal roofing, such as Colourbond or Zincalume, is common in Australia. It is durable, aesthetically pleasing to the eye, can be layered over an existing roof and it is also the most cost-effective option.
Asphalt shingles are growing in popularity in Australia. They are easy to install, generally low maintenance and very tough. They come with a warranty of 40 years and being lightweight, are easy to transport. As well as the tile costs alone, bear in mind that you will also need a plywood waterproof backing and underlay, which will bring the cost up. Installation costs will also need to be added.
Concrete tiles are hardwearing and have the advantage of reducing heat loss and noise levels from the outside. They come in a range of colours and styles to suit all profiles and design requirements and are slightly cheaper than Asphalt Shingles.
When replacing your roof, take advantage of the Australian sunshine and consider incorporating some solar energy tiles to meet your hot water or pool heating needs. Solar tiles are 25% lighter than a standard roof tile, and allow you to utilise solar power without compromising the look of your roof. Solar tiles blend seamlessly into your roof and provide the ideal solution to your green energy requirements. Some solar tile installations may qualify for a rebate or incentive from your State Government and will need to be installed by a suitably qualified technician, as recommended by your renovation specialist.

Looking for inspiration? Check out this home extension for a growing family in St Kilda, completed for $205,000

This home renovation advice article featured on page 84 of Issue 016 of New Zealand Renovate Magazine. New Zealand's first and only magazine solely dedicated to home renovations.

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*Costs are rough estimates and are subject to change - GST is not included unless otherwise stated. For a fixed-quote accurate to your specific project, please consult your local Refresh Renovations specialist. All Refresh Renovations franchises are independently owned and operated.

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