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The new Centre for Cities report – Breaking the Bottlenecks – sets out a range of anti-supply measures the Government should reform to reach its target for 1.5 million new homes.
Centre for Cities writes:
The Government has made progress on planning reforms to allow more greenfield development in the shires, but building houses remains a challenge. Construction costs have risen, and many sites have stalled. In our new report Breaking the Bottlenecks we identify five key ‘anti-supply measures’ as policies that fail to meet their aims, create unintended consequences, and are treated differently abroad. Below is a summary of these issues and our proposed reforms.
Minimum Space Standard for One-Bed Flats
Many renters in England, particularly in cities, live in shared housing because living alone is unaffordable. A key reason is that space standards are set too high. The legal minimum size for a flat is 37m², while the average renter in London can only afford 25m² (29m² nationally). Developers often build to the 50m² standard for couples, meaning most one-bed flats are nearly double what single renters can afford. This is akin to setting a minimum wage above the average wage. Rather than improving affordability, it stops homes from being built. Reforming the space standard would not affect overcrowding laws but would make solo living more attainable and free up family homes currently used for flatshares.
- Proposed reforms: Reduce the minimum to either 25m² (the Japanese standard) or 18m² (the Dutch standard). This would enable developers to build more affordable units and support housebuilding by aligning with what people can afford.
Overheating Regulations and Air Conditioning
British cities are getting hotter, and regulations require new buildings to prevent overheating using only passive measures like ventilation. Air conditioning is generally not allowed except in exceptional cases. These rules conflict with each other: they require small windows (to reduce solar gain) while also demanding ‘dual aspect’ layouts with windows on multiple sides, forcing awkward and expensive building designs. Passive cooling fails in extreme heat. Air conditioning, which is becoming more viable as the grid decarbonises, offers a reliable and practical solution. Since air conditioning units are heat pumps, allowing them would also encourage heat pump uptake in flats.
- Proposed reforms: If the Government insists on passive cooling, it must resolve contradictions between national and London standards. Alternatively, air conditioning units should be a possible route for compliance with the overheating rules, as other countries do.
Dual Staircase Requirement at 18 Metres
Following the Grenfell tragedy, new rules require dual staircases in residential buildings over 18 metres. While well-intentioned, the safety benefit is minimal – only a 6 per cent evacuation improvement in 18m buildings – and doesn’t justify the massive cost. An impact assessment estimated that £9 million in benefits from safety would cost society £2.7 billion, disproportionately affecting buildings between 18 and 50 metres. The requirement reduces the size of flats, increases costs, and complicates compliance with other rules like dual aspect.
- Proposed reforms: Raise the threshold to either 30 metres (the original proposal) or 50 metres, as in France. Other countries like Austria, Germany, and Singapore have limits above 50 metres.
Building Safety Regulator (BSR) Delays
At 18 metres, developments must go through the BSR’s ‘Gateway’ approval system. Yet in 2024, only 14 per cent of applications passed Gateway 2, with over 800 projects stuck in limbo. What was meant to be a 12-week process now causes delays of up to two years. Local authorities, who oversee Gateway 1, are incentivised to meet housing targets. The BSR is not. This creates a bottleneck.
- Proposed reforms: In the short term, require the BSR to issue conditional approvals. Longer-term, either embed the BSR within a reformed regulator focused only on higher-risk buildings (above 30 or 50 metres), or abolish it and return control to local planning authorities, as was the case before 2023 and remains typical abroad.
Biodiversity Net Gain (BNG) Costs
The Environment Act 2021 requires most developments to deliver a 10 per cent increase in wildlife habitats, with credits available for off-site mitigation. This system hits brownfield sites hardest, particularly derelict land in cities, which has little space for new greenery. The result is an incentive for suburban sprawl and a disincentive for urban regeneration. BNG’s costs are especially severe in the North and Midlands, where land values are lower and margins tighter. Some industrial sites (like ‘Open Mosaic Habitat’) face extreme penalties. No other country has a biodiversity policy as expansive or costly.
- Proposed reforms: Either reduce BNG credit values for brownfield sites or exempt such land entirely.
The Combined Impact
Each of these anti-supply measures are problematic on their own, but their combined impact is even more restrictive. Take Block 3 in the Cockfosters development: although it had two staircases, the 18m thresholds for staircases and the BSR forced lots of floors to be cut, halving its size from 107 to 47 flats. This kind of ‘chopping’ is becoming more common as developers try to sidestep these rules. If this trend continues, 47 flats could become the new ceiling for city developments. Reforming all five measures could unlock far more housing than initially planned. At Cockfosters, changes to space standards and other rules could enable the original design to include 214 homes, or up to 300 in two towers each of 50 metres. That’s a sixfold increase. Such scale is what is needed if the Government is serious about hitting its 1.5 million homes target. Without reform of the anti-supply measures, that goal will remain out of reach.
