I was recently invited to deliver a guest lecture at Buckinghamshire New University, and the brief was simple enough: talk about innovation in property development. But I didn’t want to give the students another predictable rundown of market cycles and planning applications. I wanted to challenge them. So I asked one question that reframed the entire session:
“What if the most valuable development land in London isn’t land at all?”
The room went quiet. Then I pointed upwards.
The asset nobody sees
Here’s the thing about airspace development that most people outside the industry still don’t grasp: we are surrounded by untapped real estate. Every flat-roofed post-war block, every 1960s housing estate, every low-rise commercial building sitting in a well-connected postcode, there is development potential sitting right on top of it, invisible to almost everyone walking past.
Industry estimates suggest airspace construction could deliver 180,000 new homes across London alone. That’s not a niche, that’s a serious piece of the housing puzzle.
In my lecture, I broke this down into the themes I think matter most, not just for students entering the industry, but for anyone trying to understand where London’s built environment is heading.
Theme 1
The economics are hard to argue with
One of the first slides I put up was a comparison. In prime central London, excavating a basement costs roughly double what it costs to build upwards. When your build costs sit comfortably below achievable sale values per square foot, the numbers speak for themselves.
But the economics go deeper than margins. Airspace development eliminates the single biggest cost in any London scheme: land acquisition. You’re not competing at auction for a brownfield plot. You’re not navigating compulsory purchase. The footprint already exists. The infrastructure is there. The postcode is established. You’re simply unlocking value that has been sitting dormant since the roof was poured.
For local authorities especially, this is significant. In Newham, for instance, there are around 17,000 homes dating from the 1950s through the 1970s, roughly half of them still council-owned. Even where flats have been sold through right-to-buy, the council retains the freehold, and with it, ownership of the roof space. That’s an asset base that doesn’t require a single acre of new land to activate.
Theme 2
The regulatory door is open, but the corridor is narrow
I spent a good portion of the lecture walking through the permitted development rights introduced in 2020 under then housing minister Robert Jenrick. These reforms were genuinely significant. They allow up to two additional storeys on certain residential and commercial buildings without full planning permission, subject to prior approval.
But I was honest with the students: the fine print matters enormously. There are strict eligibility criteria around when the building was constructed, where it sits, and how high it can go. Layer on the fire safety thresholds that kick in at certain heights, and viability can become questionable very quickly.
These aren’t trivial constraints. The Building Safety Act has added further complexity on top. Approvals are running at three times the original target timeframe. And 3 out of 4 applications have been rejected for missing or inadequate information. The regulatory intent is sound, but the execution has created a bottleneck that has stalled projects and shaken investor confidence.
I told the students something I believe strongly: regulation isn’t the enemy of airspace development. Bad regulation is. The industry needs clarity, consistency, and a framework that distinguishes between new-build and regeneration projects. Airspace schemes often improve the fire safety and energy performance of the buildings they sit on, but the current system doesn’t always recognise that nuance.
Theme 3
Construction methodology isn’t a detail, it’s the whole game
This is where the lecture got technical, and I could see the architecture and construction management students lean in. Airspace development lives or dies on how you build, not just what you build.
Modular and offsite construction isn’t a nice-to-have in rooftop projects, it’s practically essential. You’re building above occupied homes. You need lightweight materials. You need speed. You need to minimise disruption to the people living below who didn’t ask for a construction site above their bedroom ceiling.
The best practice I shared, drawn from Populo Living’s design guide for Newham, centres on a few non-negotiable principles: dimensional consistency with the host building’s structural grid, so loads align with existing walls and columns; modular services with integrated heating systems; lightweight external finishes with exemplary fire and insulation performance.
That said, offsite construction comes with its own complexities. Not every lender will fund costs incurred at the factory stage. Where new meets old, fire separation and insulation need careful thought. And however much you standardise, every host building has its own structural conditions that the design has to work around.
Theme 4
Design quality is not optional
I made a deliberate choice in the lecture to spend time on aesthetics and design principles, because this is where airspace development has earned its worst reputation. There are examples, more than the industry would like to admit, of developers slapping cheap extensions on tired buildings and calling it housing delivery.
That’s not what this should be. The best airspace projects treat the extension and the existing building as a single design composition. High-quality materials and considered detailing throughout. Strong sustainability and energy performance credentials built in from the start, not retrofitted as an afterthought. Dual-aspect units wherever feasible.
And crucially, the existing building should benefit too. Improving the energy performance, fire safety, and shared spaces of the existing building, these aren’t add-ons, they’re integral to the proposition. Airspace development should leave the whole building better than it found it. That’s the deal. That’s how you earn resident support, planning consent, and long-term value.
Theme 5
Residents aren’t obstacles, they’re stakeholders
This was probably the part of the lecture I felt most strongly about. The biggest challenge in airspace development isn’t structural engineering or planning policy. It’s people.
Across London, proposals to add new floors above existing housing blocks have drawn significant local opposition. Residents raise legitimate concerns about construction disruption, changes to neighbourhood character, and the fundamental issue of leaseholders having no meaningful control over what happens above their heads. In some cases, projects have stalled entirely before a single crane has arrived.
I understand those concerns. Anyone would. And the industry has to stop treating community opposition as an inconvenience to be managed and start treating it as feedback to be incorporated.
The better approach, and the one I advocate, puts residents at the centre of the process from day one. That means involving them from initial design through to the works programme. It means considering upgrades to the existing building where feasible, whether that’s communal areas, lifts, hallways, or energy performance improvements. It means reviewing and enhancing fire prevention works as part of the overall scheme. It’s not just about adding homes on top, it’s about improving the homes below wherever possible.
Where this goes next
I closed the lecture with a reality check. The pre-pandemic promise of 41,000 new homes through airspace development hasn’t materialised. Only 2,158 private homes began construction in London in the first half of 2025, a historic low. Rising costs, regulatory uncertainty, contractor insolvencies, and investor retreat have created what can only be described as a perfect storm.
But the fundamentals haven’t changed. London has the oldest housing stock in Europe, with around 60% built before World War II. There is virtually no appetite or permission to demolish 200-year-old buildings to build new ones. Land in connected locations is impossibly scarce. And the climate imperative demands that we retrofit and extend existing buildings rather than perpetually building on greenfield sites.
Airspace development isn’t a trend. The case writes itself. The question isn’t whether London will build upwards, it’s whether we’ll do it well.
I left Buckinghamshire New University hopeful that the next generation of developers, architects, and planners will bring the rigour, creativity, and community-mindedness that this sector desperately needs. The opportunities are literally above our heads. We just need to look up.
