The National Housing Accord is currently struggling to meet its pledge of 1.2 million new homes by 2029. Land remains ruinously expensive, builders are exiting the market in record numbers, and planning approvals routinely stretch past a year.

Yet a walk through Sydney, Melbourne or Brisbane reveals a counterintuitive asset: thousands of flat roofs carrying nothing more than air-conditioning units and stray pigeons. If those few hundred square metres were at ground level, they would cost millions. But in the sky, they are effectively free. Better still, many post-war office and residential blocks were engineered to carry extra weight.

Airspace construction capitalises on this structural headroom. Lightweight timber, cross-laminated timber (CLT), or light-gauge-steel modules can be fabricated off-site, craned into place within days and plugged seamlessly into existing services while businesses or apartments below continue trading or remain as residences.

Reusing an existing concrete frame avoids around three-quarters of the embodied carbon found in a new tower. Meanwhile, every rooftop resident makes use of the pipes, rails and fibre that are already in the ground. Global precedents abound: London has experienced a significant increase in rooftop homes in recent years, while Rotterdam is turning 18 square kilometres of flat roofs into housing, solar and rain-capture infrastructure. CBRE’s Australian market analysis describes local rooftop potential as “tens of billions” of dollars waiting to be unlocked.

Sceptics need look no further than 55 Southbank Boulevard in Melbourne, where ten storeys of CLT were added above a 1989 concrete office block. The extension delivered 220 hotel rooms in under twelve months, sequestered 4,000 tonnes of CO2, all while causing minimal street disruption. This is robust evidence that much of the engineering, supply chain and regulatory pathways already exist here at home.

A five-step pathway

To roll out rooftop housing at scale, we propose five key policy steps.

1. Map and measure the opportunity
   A national survey in coordination with Geoscience Australia could create an atlas of every suitable roof for new housing. Flat roofs constructed after 1950 could be identified using LiDAR (a 3D laser scanner) and drone imagery, and then merge it with data on ownership, zoning, infrastructure and estimated structural capacity. Empowered with this data, councils, developers and investors could discover feasible sites in minutes instead of months. Countries, including the United Kingdom, have pioneered innovative methods for measuring and mapping the potential of rooftop housing, which could be applied in Australia.
2. Rewrite the rulebook for approvals
   England’s national policy on roof extensions is comparatively simple: an extension can effectively bypass the planning process if it meets a set of pre-defined criteria. Australia could graft a similar “if-it-fits-it-passes” test into the National Construction Code (NCC). Certifiers, rather than overloaded council planners, could sign off on compliant, high-quality schemes, significantly reducing approval times. Meanwhile, nationally consistent weight limits of no more than 3 kilonewtons per square metre would nudge proponents toward low-carbon timber and steel.
3. Proof of concept on public assets first
   State-owned commercial buildings and car parks offer the perfect laboratory for rooftop housing. By approving planning for just twenty suitable sites and tendering them exclusively to modular builders, governments could potentially inject 1,000-2,000 dwellings into the pipeline.
4. Align the money with the mission
   Half of any air-rights proceeds should be earmarked for lifts, solar arrays and façade upgrades, turning existing owners into passionate advocates rather than objectors. Housing Australia could add a $500 million concessional debt window for rooftop projects that cut embodied carbon by at least 40 per cent and reserve one-fifth of apartments for key workers or sub-market rents. Clear GST and stamp-duty guidance would remove the final fiscal grey areas.
5. Build the skills and the factories
   TAFEs need to develop microcredentials in adaptive-reuse design and volumetric installation before demand surges. Advance-purchase agreements for CLT and light-steel frames would give manufacturers the certainty to expand production lines, smoothing the boom-bust cycle that plagues conventional residential construction.

Managing risks

Structural safety can be addressed through a federally endorsed checklist that confirms column capacity, vibration and wind limits with a generous 30 per cent buffer. Neighbour amenity concerns can be defused by mandatory setbacks, green roofs and glare-reducing façades. Construction staging plans should guarantee no more than five days’ utility interruption for existing tenants. Extensive off-site fabrication makes that target realistic.

Stringent fire-rating requirements (AS 1530 compliance with AS 5113 façade tests) mirror standards have already been applied to mass-timber mid-rise buildings. Because pioneers often face steep insurance premiums, a federal re-insurance pool similar to North Queensland’s cyclone scheme could cap the cost until actuarial data mature.

Governance: who does what

Coordinated action would be needed between all three levels of government. At the Commonwealth level, Canberra would need to amend the NCC, seed the Green Rooftop Housing Fund through Housing Australia and bankroll the national scan. States would need to fast-track pilots on their own assets, harmonise strata legislation so air-rights deals can proceed with minimised legal risk and publish structural assessment guides through their building commissioners. Local governments would have to update environment plans to recognise compliant rooftop work as code-assessed development and could offer rate rebates where projects deliver community benefits such as solar, stormwater retention or public terraces.

Industry consortia could standardise “airspace kits” that integrate design, manufacture and installation, while super funds could structure long-lease debt products targeting rooftop rental blocks.

Measuring and envisioning success

By 2029, Australia should aim for at least 50,000 completed rooftop dwellings, saving 3 million tonnes of embodied CO2 and shrinking approval times for compliant schemes to less than two months. A fifth of those homes would be reserved for teachers, nurses and other essential workers. Modular construction’s share of multi-residential projects could climb from today’s single digits to 20 per cent, underpinned by a steady workflow for factories and predictable labour demand.

So, what would this mean for our cities? Envision a revitalised Brisbane where student studios crown 1970s car-park decks, their façades wrapped in lush solar-shading greenery. Picture Perth office blocks sporting setback duplexes whose sale proceeds have paid for new lifts, electric-vehicle chargers and rooftop childcare centres for existing tenants. In Sydney, timber penthouses rest lightly atop sandstone heritage warehouses, capturing harbour breezes while locking away carbon. Residents walk or cycle to work, councils collect fresh rate revenue, and builders enjoy year-round factory shifts untroubled by rainy days.

Look up, build up, move forward

Rooftop housing offers a rare policy “unicorn” that aligns the interests of the public purse, environmentalists, the construction sector, landlords and tenants. Every module craned onto a CBD roof refreshes stamp-duty revenue without bulldozing a paddock on the urban fringe.

Australia’s housing debate has spent decades staring at ever greater distances in search of developable land. The cheapest block in the country, however, is the one we already own: the thin slice of air above every flat roof from Perth to Parramatta. By mapping that resource, recoding approvals and piloting on government buildings, we can convert idle rooftops into our fastest, greenest housing pipeline. The sky is no longer the limit; with a determined shift in policy and practice, it can become the launchpad for 150,000 much-needed homes.

Dr Ehsan Noroozinejad is a Senior Researcher at the Urban Transformations Research Centre, Western Sydney University, where he specialises in Smart, Resilient & Affordable Housing. He is also the Global Challenge Lead at WSU on Sustainable Futures. He has recently received a Policy Challenge Grant from the Australian Public Policy Institute on affordable and Net Zero housing.

The following experts also contributed to this article.

Barrie Harrop is an Australian placemaker and entrepreneur with over 40 years’ experience in large-scale premium housing and building developments nationwide. He serves as the Executive Chairman of Thrive Construct, a company dedicated to innovative, sustainable and affordable housing solutions.

Warren Livesey is the Founder of the Association of Rooftop & Airspace Development, the Executive Director of Strata Council, and the Founder of Buy Airspace, with over 28 years of experience across London, New York and Sydney. He helps transform unused rooftops into new homes, modernising ageing buildings, easing housing pressure and extending urban sustainability.

Professor Greg Morrison is the Lang Walker Endowed Chair in Urban Transformation and the Co-Director of the Urban Transformations Research Centre at Western Sydney University. Greg is a leader in sustainable and thriving cities who has made a demonstrable impact in the circular economy, Net Zero, living labs and climate adaptation and innovation.

Image credit: Michal Collection