The Building Safety Act is not the only barrier to building upwards,’ Chris Hemmings of Carter Jonas explains, so what needs to change to unlock delivery?
The word ‘density’ is increasingly used in the context of planning and development. In places with the greatest need for new homes, land is scarce, boundaries are tight and opportunities to expand outwards are limited. In those circumstances, building more homes almost inevitably means building more densely.
Unpacking the density gap
And yet the UK is failing to do so. Centre for Cities’ report Flat Britain: The urban density gap and how to close it shows that if British cities were built at the density of their French or Japanese peers, they would contain at least 2.3 million additional homes across their urban cores. Furthermore, if the density of London’s urban core (Zones 1 – 3) matched that of Paris, the capital would have at least 500,000 more homes. The problem is not limited to London: the report also states that the density gap is greatest in Britain’s big cities outside of London – these 12 alone comprise over half of the total gap.
Recent data from the Greater London Authority (GLA) shows that the number of flats and houses being built has declined in each of the past three years, from 38,987 in 2021-22 to 28,756 in 2024-25. In the first half of 2025 , fewer than 2,200 homes began construction in London, according to data from Molior, compared with 8,500 in the first six months of 2022 and more than 13,500 in the first half of 2018.
Additionally, GLA data shows that London’s housebuilding has fallen to its lowest level in more than a decade and cites the difficulty in getting official approval to build flats from the building safety regulator after the cladding crisis.
That logic for higher density is well understood by planners and policymakers: it is acknowledged that higher-density development supports sustainable transport, makes better use of existing infrastructure and helps to underpin town centres and local services. In theory, it is an efficient response to constrained urban conditions. In practice, delivering density has become increasingly difficult, due to market and regulatory factors.
Now more than ever, there is a substantial gap between the political ambition for density (which will be fundamental to housing targets being met) and delivery on the ground. This is most evident in London, though the issues are increasingly apparent across other urban areas too.
New bottlenecks emerge
The Building Safety Act 2022 was introduced with the important objective of tightening the regime and restoring confidence in higher-risk buildings following the Grenfell Tower fire. Few in the industry would dispute the need for a stronger safety regime and more effective oversight. However, its implementation has brought with it approval bottlenecks with knock-on effects for how and where developers are prepared to build.
The requirement for Building Safety Regulator sign-off at Gateway 2, before works can begin on higher risk buildings, has introduced a new layer of uncertainty into development programmes. Target timescales are frequently exceeded, and in the absence of settled precedent, developers are often unable to predict how long approvals will take. For schemes that rely on height to achieve viability, this uncertainty quickly becomes a material risk.
Cost pressures mount
The problem is compounded by cost pressures. The requirement for second staircases in buildings over 18 metres reduces net internal area and efficiency. Furthermore, compliance costs add up across design, procurement and construction and taken together, these factors have encouraged a shift away from taller buildings towards mid-rise.
The forthcoming Building Safety Levy (proposed for October 2026) adds another layer to an already complex viability picture. Although the levy is modest when viewed in isolation, it does not operate in isolation – sitting alongside high affordable housing requirements, biodiversity net gain, energy performance standards and Community Infrastructure Levy (CIL) charges, all at a time when the government’s Help to Buy scheme was phased out and registered providers focused investment on their existing stock.
On marginal urban sites, where density is often the only route to making schemes stack up, these cumulative burdens matter. The levy is payable early in a scheme’s life and in full, which has implications for cashflow as well as headline viability. For larger developers this may be absorbed, albeit reluctantly. For SME developers who lack the same economies of scale, the impact is proportionally greater.
Policy responses
Due to the rapid slowdown in completions in London as a result of recent regulatory changes and general market conditions, the GLA is consulting on changes to its affordable housing policies for a temporary short period to help stimulate the development market, most notably a reduction in the fast-track affordable housing planning route threshold from 35% to 20% on privately owned sites. The government is also consulting on providing CIL relief for residential schemes in London, also for a short-term period. Whether the short period of time for implementation makes a real difference to market activity, remains to be seen.
Moreover, these changes may call into question the introduction of the Building Safety Levy , or provide justification for greater relief for residential schemes where viability is already problematic.
Alongside safety and cost, potential leasehold reform adds another layer of uncertainty. The government has stated its ambition to move towards commonhold for new flats and is currently consulting on a Draft Commonhold and Leasehold Reform Bill. However, the timing and practical transition could significantly impact development output.
Commonhold remains largely untested at scale in England and Wales. The majority of developers are cautious about being early adopters, lenders remain unconvinced about risk and security, and buyers are wary of a step into the unknown.
The outlook
From my perspective, a balanced approach is essential. Reforming leasehold to address its shortcomings while building confidence in commonhold over time would allow the market to adjust. Moving too quickly risks undermining the apartment market on which higher-density delivery depends.
There are ways to reconcile density with safety and deliverability. Mid-rise buildings, typically between six and ten storeys, can achieve high densities without triggering the most onerous aspects of the higher-risk regime (although any residential scheme of 7 storeys or at least 18 metres high requires approval from the Building Safety Regulator). Mansion blocks and perimeter blocks deliver efficient layouts and good amenity while sitting comfortably within established urban fabric.
Construction methods also matter. Robust structural systems, simple geometries and repeatable design solutions are easier to verify and less prone to delay. Early engagement with the regulator, particularly where modern methods of construction are proposed, can reduce risk later in the process.
Crucially, the regulatory system itself could evolve. A more proportionate approach for simpler or mid-rise schemes, clearer guidance on gateway submissions and better integration between planning and building control would all improve predictability without compromising safety.
The need for density is not going away. If anything, it will intensify as housing targets remain under pressure and urban land becomes scarcer. The question is whether the current framework allows that density to be delivered at scale.
This article was written by Chris Hemmings, partner at Carter Jonas.
Images: Anthony Fomin/Unsplash and Chris Hemmings
Other features:
Leave a Reply