The impact of the Building Safety Act in reducing structures heights

The news recently has been rife with ways on how to improve buildings’ fire safety. However, Carter Jonas’ James Staveley, examines how the development of tall buildings will be affected by such changes. 

Following the 2017 Grenfell fire, the issue of fire safety within high-rise residential blocks has come into sharp focus. It had become abundantly clear that the UK needed to update regulations to prevent such a tragedy happening again. In Summer 2023 the government announced that the threshold for the introduction of second staircases into new residential buildings would be reduced to 18 metres, effectively in the region of seven storeys in height. This was an update on announced plans in late 2022 that second staircases would be required in buildings of over 30 metres. Although the government have published and confirmed its building safety guidance for second staircases to be implemented, in October last year it was revealed that there will be a 30-month transitional period from when they will be introduced. 

So how will the new regulations impact the development of tall buildings?

The new policy will reduce the sales areas within schemes: traditionally, developers of residential towers in urban areas aim for at least 80% of a floor plate as ‘saleable’ (individual apartments for sale, as opposed to circulation spaces). With the requirement for a second staircase and the additional corridor area that this necessitates, the ratio of saleable area to circulation space would reduce by approximately 5-10%.

In parts of London, on an eight-storey development, this could result in a reduction in gross development value by maybe £1-2m per floor and a total reduction of possibly £15m or more. Clearly, this has a significant impact on the land values anticipated by landowners and could even lead to challenging viability when coupled with other factors such as escalating build and finance costs and affordable housing.

In instances where land has been purchased at a premium, developers may then look to use the requirement for an additional staircase to argue for reductions in the levels of affordable housing from policy-compliant levels.

Alternatively, developers may look at options to reduce the height of developments to below the 18m threshold, maintaining the strong relationship between a building’s footprint and saleable area. Whilst this would result in fewer units, it could be that for landowners promoting such schemes through the planning process, a ‘less is more’ approach is sought instead, to maximise the land value. Certainly, there would appear to be limited commercial value in pushing to promote for a development with a single additional storey – which could result in more units but may introduce a requirement for a second staircase. As such, it is likely that future schemes will either be below 18m or will be considerably higher.

This would then have a knock-on effect on urban councils, which need more housing to support a growing population. Sites which have previously been consented for eight, nine or ten storeys may no longer be viable. This would especially impact parts of Zones 3-6 in Greater London. With limited land supply for new residential schemes, there is a preference for taller developments in these locations, where sales values in the region of £650-£800 per sq ft may be anticipated. Councils in such areas may potentially be forced to look at additional or alternative sites for housing.

Developers who chose to submit a planning application for a lower height development than previously consented may be criticised for under-development, even if such a scheme is demonstrated to be the optimum financially and delivers policy-compliant levels of affordable housing. And whilst some councils may accept a reduction in scale, this will lead to a decrease in CIL revenues, which could impact investment in local services. There would also be fewer affordable housing units delivered overall as the number of such units is based on a percentage of total units constructed.

The alternative may be for even taller developments than had previously been considered appropriate. This will greatly increase density, which apart from being very controversial, may, in some circumstances exacerbate social problems.

There is a strong possibility that the design and density of buildings will change: the days of eight-storey development could be limited with a preference for either developments to be reduced to seven storeys or below. The impact on tight development sites is likely to be greatest. Having once exceeded the height threshold to enable a second staircase to be included as a part of a scheme a developer will likely push the height as much as possible to maintain a gross development value to compensate a reduced gross-to-net ratio. For a scheme on the cusp of the requirement for a second staircase, the developer’s preference would probably be for a decreased height, unless they can secure reductions in the levels of affordable housing. The alternative might be for developers to absolutely maximise building footprints and minimise the impact on the saleable area.

Either way, this very significant legislation will change both developers’ approaches to tall buildings and city skylines too.

Images: João Barbosa and Sean Pollock

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