Ben Derbyshire and Riette Oosthuizen outline a strategy for making better use of land
Supurbia is a strategy for intensifying London's suburbs that balances their inherent advantages with higher density and amenity value. Its approach is twofold: redeveloping local main streets and parades as mixed-use places with increased housing, improved service and amenity provision; and, enabling owner-occupiers to develop their land, creating rich diversities of housing.
This vision for intensifying suburban London with high quality development is about local planning authorities and local residents within a neighbourhood working together, with a facilitator, to draw up suitable options for the redevelopment of privately owned properties, and for the public realm in the wider neighbourhood area. These would then be adopted as a Local Development Order (LDO). LDOs are a mechanism by which this range of standard design solutions can be pre-approved (i.e. granted planning permission) and from which householders can select their preference, without having to apply for planning permission at a future date – more or less equivalent to permitted development. LDOs are typically applied to a defined area such as a neighbourhood or block. Neighbourhood plans themselves could also be the route to the designation of such areas within Local Plans. For neighbourhood planning a group would have to be formally established and the neighbourhood boundaries approved by the local authority. Aside from the potential cost of extensive consultation, the neighbourhood plan would have to be approved via a neighbourhood referendum. Local planning authorities could proactively encourage the formation of such groups. Nevertheless the costs of these processes could be met by the promoters of redevelopment or by those with major regeneration schemes seeking to engage with the surrounding neighbourhoods.
The process of creating a Local Development Order would create a range of 'plot passports' (a form of permitted development) for all homeowners within the neighbourhood. Plot passports would be a menu of redevelopment options available to all homeowners within the neighbourhood to redevelop their property or land. They could choose to exercise these options, or opt out entirely. One homeowner opting out would not prevent another homeowner from going ahead, although this would prevent collaborative options with immediate neighbours.
Initially the Supurbia policy would be about focused area-based schemes near under-developed transport hubs where urbanisation could create increased values, like ripples in a pond, triggering intensification in a variety of typologies. This could transform the poorer, often subtopian areas of London's heavily concreted and low density suburbia into a vision of thriving, vibrant and sustainable place-making – the Supurbian vision.
Financial incentives for homeowners
We have evaluated the likely increase in value as a consequence of development by individual homeowners, after development costs, and any value reductions due to reduced garden sizes. The results indicate a realistic level of financial incentive for homeowners to exercise their redevelopment options in most cases. Our preliminary studies show that homeowners may benefit from net development profits of £110,000-210,000 per household, depending on the redevelopment option and typology adopted.
Changes to planning
Back garden land is generally protected, but not all London boroughs take an entirely protectionist approach. Backlands have been given added protection in the National Planning Policy Framework (NPPF) when it was reclassified from brownfield to formerly undeveloped land. However, the NPPF makes it clear that the key consideration should be whether new development would harm local character. We believe that a carefully considered design-led and consultative approach would improve the character of certain suburban areas.
Householders already have a wide range of permitted development rights, such as the ability to extend their homes by up to 50 per cent of the curtilage of the original house; back or side extensions of up to 6 metres in the case of semi-detached and terraced homes (or 8 metres in the case of detached homes); and, loft extensions by up to 40 cubic metres for terraced homes and 50 cubic metres for detached homes. However, the current permitted planning rules do not allow for buildings to be constructed within land that surrounds a house for the purpose of being lived in (i.e. having a plumbed-in and self-contained bathroom and/or kitchen).
Back gardens are widely valued because of their contribution to biodiversity. The development of back gardens does preclude equal or increased amounts of biodiverse rich landscaping being put back – particularly with the use of living roofs. So permitted development rules could be changed to allow self-contained homes to be built on land surrounding an existing house, where the design specification has been agreed with the neighbourhood, most probably through a neighbourhood plan.
Funding plot passports
Outer London is now peppered with an increasing array of housing zones, opportunity areas, local authority estate redevelopments and major brownfield developments, particularly around new transport infrastructure investment. Many, if not most of these appear to be incongruous islands of high-density housing threatening to overbear the surrounding suburban neighbourhoods. It is not uncommon for densities in such projects to rise to 350 homes per hectare – i.e. superdensities which exceed the density of surrounding neighbourhoods by ten times or more.
We envisage that the joint venture partnerships formed by local authorities, developers and housing providers to deliver these gargantuan projects may see the virtue in engaging with residents of the surrounding suburban hinterland, and many of whom might otherwise be in entrenched opposition to what are seen as interloping alien developments. In our experience opposition and support are opposite sides of the same coin, and one can turn to the other if there is appropriate incentive.
Therefore these development consortia may be willing to sponsor neighbourhood planning in the interests not only of quelling potential opposition, but also because participation in urban intensification around their projects would add value to their investments. If so, we foresee that suitable pilot areas could be identified, and local authorities could collaborate with residents and sponsor community advocates to undertake neighbourhood planning exercises designed to nest suburban improvement areas within Local Plans.
The design-led approach
The next stage is the development and testing of the designs for the range of typologies in more detail. This is a design-led and technical process in which procurement and construction issues would be worked through. The premise is that the standardised nature of semi-detached suburbia is such that this exercise will produce a range of solutions capable of meeting the regulatory challenge in most circumstances. These solutions would therefore become standard templates within the framework of Local Development Orders – enabling the rapid adoption of pre-approved typologies in a wide range of settings.
An analysis of plots would produce sets of suitable solutions for the intensification of back garden land and the redevelopment of existing buildings, as indicated on plot passports and comparable to outline planning permissions. These would incorporate planning considerations such as sunlight, daylight, back-to-back distances, the retention of valuable trees and suitable amounts of open space, and could give guidelines on how to reinvest some of the home owner's new financial gain into improving the environmental efficiency of their own home. Tax Increment Financing could become a method for funding improvements to neighbourhood energy systems and area improvements to the public realm to accompany the investment in individual and groups of private homes.
Overall this process enriches our limited suburban housing stock with a spectrum of options. Instead of the undifferentiated one and two bedroom homes that dominate many large scale developments, this would include family homes with gardens, investor Private Rented Sector schemes, accessible ground floor older people's accommodation (bungalows), and affordable starter houses for new households. Plot passports would enable local authorities to agree parameters on the range of sites within a neighbourhood, optimising the quantum and mix of development, and promoting investment by custom builders, small investors and builders.
High quality offsite manufacturing
The plot passport menu of options would comprise online design catalogues for homeowners to choose high quality, pre-manufactured yet durable housing options exceeding London standards. Groundwork can be minimised through the use of lightweight prefabricated structures and the experience of construction using premanufactured structural insulated panels (SIPS) is that disruption is minimal. These techniques would maximise speed and minimise inconvenience, helping to preserve existing communities and taking full advantage of existing infrastructure.
As well as increasing housing supply and improving London's suburbs, the Supurbia concept has the capacity to liberate equity locked up in relatively poor quality private housing stock by facilitating home owners to participate in profitable development, which will also increase supply and improve neighbourhoods. The design-led approach, based on Local Development Orders and approved plot passports would guarantee a high quality outcome.
Starting with pilot studies in the hinterland of large scale urban regeneration schemes in London would enable local people to participate in the betterment of their neighbourhoods and thus become advocates for, rather than opponents of, urban intensification and new housing development, turning NIMBYism on its head or turning NIMBYs into YIMBYs (Yes – in my back yard!).
This article first appeared in the Urban Design Group Journal, Spring 2016 edition.