Watch this space: In-filling London’s roofline

29 Aug 18

What if I told you that in London we could build 40,000 new homes in Zones 1 and 2 without releasing another centimetre of land? I suspect you would look at me with a mixture of awe and pity at the scale of my delusion.

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What if I told you that in London we could build 40,000 new homes in Zones 1 and 2 without releasing another centimetre of land? I suspect you would look at me with a mixture of awe and pity at the scale of my delusion.

Yet, recent studies have exposed the potential to do just that; by utilising the gaps that appear in the roofline when streets are formed from a mix of low and mid-rise buildings.

Knight Frank’s comprehensive ‘SKYWARD’ modelling cross-references the Ordinance Survey and Land Registry data to create a 3D model of empty spaces in the skyline, predicting that in Zones 1 and 2 there is space in London’s roofline for 40,000 new homes. While Apex Airspace put this figure at 140,000 across Greater London.

With brownfield land becoming increasingly scarce in London and land values surging, it is an opportune time to start considering more innovative approaches to increasing density. Building tall, slender towers is not always the most efficient way to achieve this; elevators and stairs can take up a sizeable proportion of the overall floor space and reception areas can negatively impact street life. The idea of extending on top of existing buildings also supports the use of less disruptive construction techniques such as modular construction, which offers faster delivery and a shorter time on site.

Inevitably, such an ambitious proposal would not be without its challenges. Convincing existing occupants will be difficult, especially considering that a 2016 MHCLG consultation showed fewer than half of respondents to be supportive of the idea – with many naturally concerned about the impact on sunlight and the potential for overshadowing.

But we should not be too quick to dismiss the idea, the revised NPPF demonstrates Government recognition for the opportunity these spaces present; with policy 118(e) stating its support for the use of airspace above existing residential and commercial premises for new homes.

Through attentive engagement with existing residents, intelligent design and considerate construction the idea could have a viable future. For example, setting the additional floors back from the edge of the existing building could mitigate the issue of sunlight, as well as helping to shorten the length and disruption of the building process.

If planners, developers and residents can be brought on board, this ‘blue sky’ thinking could present an alternative way of reducing London’s housing pressures.

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