Supurbia
Ben Derbyshire and Riette Oosthuizen, HTA
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 the 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. The strategy will bring together local authorities and communities to plan appropriate developments, and allow homeowners to release equity in their land for home improvements. It will also reduce reliance on mainstream developers to ease the housing crisis, providing an approach that is more adaptable to communities’ needs.
Transforming Metroland
The main Supurbia idea addresses the streets of semidetached housing behind main roads. With an estimated 24% of London’s land classified as rear gardens, suburban plots consume a disproportionate amount of land. The typical suburban plot, at 8m wide and 40m deep, often accommodates no more than a two storey house with a footprint of 7.5m by 6m. So a mere 15% of the plot is actually built on, which could easily rise to 30%, not only leaving plenty of green space as gardens but potentially without any loss of greenspace - replacing large sheds with new homes and grassing over concrete verges are some obvious examples. These plots and the houses that sit on them also display a remarkable degree of consistency owing to the standardisation of approach adopted by their developers – often Wates and John Laing, the leading housing developers of the inter-war years. This uniformity lends itself to a standardised design lead approach to augment the housing provision that is described in what follows.
The vision for intensifying suburban London with consistent high quality development is for the Local Planning Authorities and the local residents within a neighbourhood to work together with a lead facilitator to draw up suitable and agreeable options for the redevelopment of privately owned properties, and of the public realm in the wider neighbourhood area. These would then be worked into a “Local Development Order”. Local Development Orders (LDOs) are a mechanism by which a range of such standard design solutions can be pre-approved (i.e. granted planning permission) so as to create options from which householders can select their preference, without again having to apply for planning permission at a future date - more or less equivalent to permitted development. LDOs are applied to a defined area such as a neighbourhood or block.
To begin the process, Local Planning Authorities could take a consultative, pro-active, but more hands-on approach in partnering with developers and off-site manufacturers, whilst ensuring that local residents are fully engaged and on board from the initial stages of working on the Local Development Orders. In this way householders would have early input on the materials palette and design options that would be suited to a particular area. These would then be incorporated into Local Plans. Under this route it is important that residents buy into the proposals and are closely involved with them from the beginning.
But actually Neighbourhood Planning might well be the main 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. Again, Local Planning Authorities could proactively encourage the formation of such groups but they could be more hands off in driving the process. Either way, we suggest that the costs of such processes could be met by the promoters of the redevelopment or those of major regeneration schemes seeking to engage with surrounding neighbourhoods.
The process of creating a Local Development Order would bring into being a range of “plot passports” (a form of permitted development) for all homeowners in the neighbourhood. Plot Passports would be a menu of redevelopment options available for all homeowners within the neighbourhood to redevelop their property. They could exercise these options if they wanted to, but equally they could refrain from doing so, if they did not want their property redeveloped. Importantly one homeowner refraining does not prevent another homeowner from going ahead, though it does obviously prevent the collaborative options with their immediate neighbours.
Just as importantly, though, it raises the opportunity for the owner of a single semi-detached house, or a pair of neighbouring or facing owners where there was collaboration between them, to exercise choices by developing their land to suit their needs; new family homes, bungalows or flats over garaging in rear gardens, or the redevelopment of pairs of existing semi-detached homes on existing street frontages. Each passport would also contain a solution that could be adopted to intensifying back garden land, depending on the degree to which householders would like to take up the opportunity on their land alone. We illustrate a possible range of plot passport options for existing semi-detached homeowners in the adjacent diagrams.
The main Supurbia idea addresses the streets of semidetached housing behind main roads. With an estimated 24% of London’s land classified as rear gardens, suburban plots consume a disproportionate amount of land. The typical suburban plot, at 8m wide and 40m deep, often accommodates no more than a two storey house with a footprint of 7.5m by 6m. So a mere 15% of the plot is actually built on, which could easily rise to 30%, not only leaving plenty of green space as gardens but potentially without any loss of greenspace - replacing large sheds with new homes and grassing over concrete verges are some obvious examples. These plots and the houses that sit on them also display a remarkable degree of consistency owing to the standardisation of approach adopted by their developers – often Wates and John Laing, the leading housing developers of the inter-war years. This uniformity lends itself to a standardised design lead approach to augment the housing provision that is described in what follows.
The vision for intensifying suburban London with consistent high quality development is for the Local Planning Authorities and the local residents within a neighbourhood to work together with a lead facilitator to draw up suitable and agreeable options for the redevelopment of privately owned properties, and of the public realm in the wider neighbourhood area. These would then be worked into a “Local Development Order”. Local Development Orders (LDOs) are a mechanism by which a range of such standard design solutions can be pre-approved (i.e. granted planning permission) so as to create options from which householders can select their preference, without again having to apply for planning permission at a future date - more or less equivalent to permitted development. LDOs are applied to a defined area such as a neighbourhood or block.
To begin the process, Local Planning Authorities could take a consultative, pro-active, but more hands-on approach in partnering with developers and off-site manufacturers, whilst ensuring that local residents are fully engaged and on board from the initial stages of working on the Local Development Orders. In this way householders would have early input on the materials palette and design options that would be suited to a particular area. These would then be incorporated into Local Plans. Under this route it is important that residents buy into the proposals and are closely involved with them from the beginning.
But actually Neighbourhood Planning might well be the main 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. Again, Local Planning Authorities could proactively encourage the formation of such groups but they could be more hands off in driving the process. Either way, we suggest that the costs of such processes could be met by the promoters of the redevelopment or those of major regeneration schemes seeking to engage with surrounding neighbourhoods.
The process of creating a Local Development Order would bring into being a range of “plot passports” (a form of permitted development) for all homeowners in the neighbourhood. Plot Passports would be a menu of redevelopment options available for all homeowners within the neighbourhood to redevelop their property. They could exercise these options if they wanted to, but equally they could refrain from doing so, if they did not want their property redeveloped. Importantly one homeowner refraining does not prevent another homeowner from going ahead, though it does obviously prevent the collaborative options with their immediate neighbours.
Just as importantly, though, it raises the opportunity for the owner of a single semi-detached house, or a pair of neighbouring or facing owners where there was collaboration between them, to exercise choices by developing their land to suit their needs; new family homes, bungalows or flats over garaging in rear gardens, or the redevelopment of pairs of existing semi-detached homes on existing street frontages. Each passport would also contain a solution that could be adopted to intensifying back garden land, depending on the degree to which householders would like to take up the opportunity on their land alone. We illustrate a possible range of plot passport options for existing semi-detached homeowners in the adjacent diagrams.
Transforming an existing rear access into a mews design that maximises private amenity space and avoids overlooking
The drawing below shows an area of South London with a typical range of suburban block typologies which would be suitable in principle for this treatment - some with rear access lanes between opposing back gardens, many with plots deep enough to permit rear garden development of the type we envisage. Having analysed such plots, we would have a set of suitable solutions for intensification.
All in all, our illustrative block begins with a density of 33 homes per hectare - a typically low suburban density. If a quarter of all plots added one dwelling, the density would increase to 45 homes per hectare. Logistically we could intensify 10% of outer London boroughs every 10 years.
Initially the Supurbia policy would be about focused, area-based, schemes centred on under-developed transport hubs where urbanisation in a concentric pattern could create outward moving contours of increased value, like the ripples in a pond, triggering the take up of intensification schemes 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 placemaking – the Supurbian vision.
All in all, our illustrative block begins with a density of 33 homes per hectare - a typically low suburban density. If a quarter of all plots added one dwelling, the density would increase to 45 homes per hectare. Logistically we could intensify 10% of outer London boroughs every 10 years.
Initially the Supurbia policy would be about focused, area-based, schemes centred on under-developed transport hubs where urbanisation in a concentric pattern could create outward moving contours of increased value, like the ripples in a pond, triggering the take up of intensification schemes 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 placemaking – the Supurbian vision.
Illustration of a typical low density suburban blocks in outer London
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Supurbia - greening of previously car dominated public realm
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Making it happen
Financial incentives for homeowners
For each of the options illustrated we have evaluated the increase of value achieved as a consequence of development by individual homeowners, netting off development costs, and any value reductions occasioned by the reduction in garden sizes. The results indicate a realistic level of financial incentive for homeowners to exercise their redevelopment options in most cases. Land would thus be intensified while preserving buildings’ individuality, and owner-occupiers could unlock the equity in their unused land and invest it in their home, raising the quality of housing across the neighbourhood and improving the street as front plots are renovated and the neighbourhood area improved (i.e. reinstating tree-lined streets) as part of the redevelopment.
Our preliminary studies reveal that homeowners may stand to benefit from net development profits of between £110,000 and £210,000 per household, depending on the redevelopment option and typology adopted.
Changes to planning
The Treasury’s Productivity Plan published on the 10th of July 2015 made it clear that the Government sees the solution to the country’s housing problem in the development of brownfield land via automatic permission for housing on such sites. But there are good reasons why brownfield land often remains undeveloped: being heavily contaminated and/or cut off from good access to public transport, the creation of well designed, good quality, popular and affordable housing without vast upfront investment and years of costly remediation seems a bit of a leap of faith.
Back garden land is generally protected, but not all London boroughs take an entirely protectionist approach. Back garden land has 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 back garden development would harm local character. We are not advocating a free for all; we believe a carefully considered design lead and consultative approach could 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 up to 50% of the curtilage of the original house, back/side extensions up to 6 metres in the case of semidetached and terraced homes from the closest back wall to the house (8 metres in the case of detached homes), loft extensions up to 40 cubic metres in the case of terraced homes and 50 cubic metres in the case of detached homes.
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Plot Passport
The plot passport concept is drawn from our experience of the emerging custom build market, applicable because of the generic standardisation of the 1930s semi-detached type. |
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Example 1
Self Build Single Plot Intensification This single plot intensification retains the main house garden up to 10m or 12m. Options show a new 2-storey, 2 bedroom mews house averaging 72sqm. Depending on the context and relationship to the main house, the design of the new mews houses are sited to the rear or front of the new plot with their private amenity space taking up the remainder. The range of options illustrated create one additional home and a typical profit of £140,000 for the homeowner. |
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Example 2
Self Build Double/Facing Plot Intensification The double plot intensification of facing homes, which share a driveway, enables the creation of a third plot at the back that utilises a portion of garden space from each of the two main homes. The illustrated options show a double storey mews house, a flat above garages (one for each of the existing and new dwellings) and a single storey accessible dwelling. The options range in size from 72 to 90 sqm. The range of options create one additional home and a typical profit of £110,000 for the homeowners. |
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Example 3
Self Build Double/Paired Plot Intensification The double plot intensification of paired homes enables the replacement of the two existing dwellings with an entirely new development that can provide a new block of flats or townhouses fronting the streets, with new garden houses to the rear overlooking the amenity spaces. The options present a range of shared or private amenity space arrangements and parking solutions. These example illustrate either 4 or 5 new homes (with a net gain of 2 to 3 homes) and a typical profit of £210,000 for the homeowners. |
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The Supurbia concept envisages suburban improvement areas where a cocktail of policy initiatives including area based local development orders (and possibly local referenda, through neighbourhood planning). Plot Passports enable the gradual take-up of development opportunities as household circumstances permit. Public realm improvements further enhance the neighbourhood environment.
However, the current permitted planning rules do not allow for buildings to be constructed within the 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).
New measures announced in the Productivity Plan will include permitted development rights to extend up to the height of neighbouring buildings - if neighbours do not object. A lot of these measures do not necessarily allow for a well-considered approach to achieving high quality design; resulting in a widely eclectic, piecemeal and at times not ideal intensification of suburban areas.
Back gardens are widely valued because of their contribution to biodiversity. However, the development of back gardens does not mean that equal or increased amounts of biodiverse rich landscaping could not be put back on site – particularly with the use of living roof coverings such as the increasingly popular sedum. So the permitted development rules should be changed to allow self-contained homes to be built on the land surrounding an existing house, where the design specification has been agreed with the neighbourhood, most probably through the neighbourhood plan. Funding the creation of Plot Passports in a neighbourhood
Outer London is now peppered with an increasing array of housing zones, opportunity areas, local authority estate redevelopments and major bownfield developments, particularly around new transport infrastructure investment. Many, if not most of these can seem like incongrous islands of high density threatening to overbear on the surrounding suburban neighbourhoods. It’s not uncommon for the density of such projects to rise to 350 homes per hectare - so called ‘superdensities’ that exceed the density of surrounding neighbourhoods by ten times or more.
We envisage that the joint venture partnerships of local authorities, developers and housing providers that have to come together to deliver these gargantuan projects may see the virtue of engaging with the populations of the surrounding suburban hinterland of their developments, many of whom can otherwise be in entrenched opposition to what may seem to them to be interloping alien developments. In our experience opposition and support are opposite sides of the same coin and one can turn to the other if only there is the appropriate incentive.
So these consortia may well be willing to sponsor neighbourhood planning in the interests not only quelling potential opposition, but also because participation in urban intensification around their projects would be a way of adding value to their investment. If so, we foresee the identification of suitable pilot areas, the collaboration of local authorities and sponsorship of community advocates to undertake Neighbourhood Planning exercises designed to nest suburban improvement areas within Local Plans.
New measures announced in the Productivity Plan will include permitted development rights to extend up to the height of neighbouring buildings - if neighbours do not object. A lot of these measures do not necessarily allow for a well-considered approach to achieving high quality design; resulting in a widely eclectic, piecemeal and at times not ideal intensification of suburban areas.
Back gardens are widely valued because of their contribution to biodiversity. However, the development of back gardens does not mean that equal or increased amounts of biodiverse rich landscaping could not be put back on site – particularly with the use of living roof coverings such as the increasingly popular sedum. So the permitted development rules should be changed to allow self-contained homes to be built on the land surrounding an existing house, where the design specification has been agreed with the neighbourhood, most probably through the neighbourhood plan. Funding the creation of Plot Passports in a neighbourhood
Outer London is now peppered with an increasing array of housing zones, opportunity areas, local authority estate redevelopments and major bownfield developments, particularly around new transport infrastructure investment. Many, if not most of these can seem like incongrous islands of high density threatening to overbear on the surrounding suburban neighbourhoods. It’s not uncommon for the density of such projects to rise to 350 homes per hectare - so called ‘superdensities’ that exceed the density of surrounding neighbourhoods by ten times or more.
We envisage that the joint venture partnerships of local authorities, developers and housing providers that have to come together to deliver these gargantuan projects may see the virtue of engaging with the populations of the surrounding suburban hinterland of their developments, many of whom can otherwise be in entrenched opposition to what may seem to them to be interloping alien developments. In our experience opposition and support are opposite sides of the same coin and one can turn to the other if only there is the appropriate incentive.
So these consortia may well be willing to sponsor neighbourhood planning in the interests not only quelling potential opposition, but also because participation in urban intensification around their projects would be a way of adding value to their investment. If so, we foresee the identification of suitable pilot areas, the collaboration of local authorities and sponsorship of community advocates to undertake Neighbourhood Planning exercises designed to nest suburban improvement areas within Local Plans.
Before
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After
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Many two storey shopping parades have the capacity for redevelopment suitable for both millennials and empty nesters, liberating the suburban
hinterland for family accommodation.
hinterland for family accommodation.
The design-led approach
The next stage is the development and testing of designs for the range of typologies we have illustrated in more detail. This is a design-lead and technical process in which the procurement and constructional issues would be flushed out. The premise is that the standardised nature of semi-detached suburbia is such that this exercise will produce a range of standard solutions capable of meeting the regulatory challenge in most of the circumstances that can be foreseen. These solutions would therefore become standard templates suitable for adoption within the framework of Local Development Orders - enabling the rapid adoption of pre-approved typologies in a wide range of settings.
Analysis of plots would produce sets of suitable solutions for intensification of back garden land and redevelopment of existing buildings, indicated on plot passports comparable to outline planning permissions. These would incorporate planning considerations such as sunlight/daylight, back-to-back distances, retention of valuable trees and suitable amounts of open space, and could give guidelines on how to reinvest a portion of gain from development into improving the environmental efficiency of main houses. Each passport would contain a range of parameters and solutions for intensifying back garden land and redeveloping existing buildings.
Property owners could select a pre-approved option or customise one within the set parameters, either developing their land alone or in collaboration with neighbours where this was an option. This concept builds on the current approach of both permitted development rights and forthcoming zoning for brownfield land; local authorities would provide additional amenities as intensification reached agreed thresholds. Each improvement will have been agreed through the Local Development Orders and tied to income generated through the development process and additional council tax revenue.
Tax Increment Financing might become the method for funding improvements to neighbourhood energy systems and area improvements to public realm that we envisage as part of the process of achieving a significant improvement to neighbourhood quality to accompany the investment in individual and groups of private homes.
This process enriches 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 will include family homes with gardens, investor PRS schemes, accessible ground floor older people’s accommodation (bungalows) and affordable starter houses for young households. Plot passports will enable local authorities to agree parameters on the range of sites within a neighbourhood, optimising quantum and mix of development. This provides opportunities to speed investment from custom build to small investors and builders.
The next stage is the development and testing of designs for the range of typologies we have illustrated in more detail. This is a design-lead and technical process in which the procurement and constructional issues would be flushed out. The premise is that the standardised nature of semi-detached suburbia is such that this exercise will produce a range of standard solutions capable of meeting the regulatory challenge in most of the circumstances that can be foreseen. These solutions would therefore become standard templates suitable for adoption within the framework of Local Development Orders - enabling the rapid adoption of pre-approved typologies in a wide range of settings.
Analysis of plots would produce sets of suitable solutions for intensification of back garden land and redevelopment of existing buildings, indicated on plot passports comparable to outline planning permissions. These would incorporate planning considerations such as sunlight/daylight, back-to-back distances, retention of valuable trees and suitable amounts of open space, and could give guidelines on how to reinvest a portion of gain from development into improving the environmental efficiency of main houses. Each passport would contain a range of parameters and solutions for intensifying back garden land and redeveloping existing buildings.
Property owners could select a pre-approved option or customise one within the set parameters, either developing their land alone or in collaboration with neighbours where this was an option. This concept builds on the current approach of both permitted development rights and forthcoming zoning for brownfield land; local authorities would provide additional amenities as intensification reached agreed thresholds. Each improvement will have been agreed through the Local Development Orders and tied to income generated through the development process and additional council tax revenue.
Tax Increment Financing might become the method for funding improvements to neighbourhood energy systems and area improvements to public realm that we envisage as part of the process of achieving a significant improvement to neighbourhood quality to accompany the investment in individual and groups of private homes.
This process enriches 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 will include family homes with gardens, investor PRS schemes, accessible ground floor older people’s accommodation (bungalows) and affordable starter houses for young households. Plot passports will enable local authorities to agree parameters on the range of sites within a neighbourhood, optimising quantum and mix of development. This provides opportunities to speed investment from custom build to small investors and builders.
New family homes accessed from existing frontages designed to maximise the private amenity, and eliminate overlooking
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Supurbia will be a more socially inclusive and convivial environment
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A new breed of SME in high quality offsite
manufactured homes
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 pre-manufactured structural insulated panels (SIPS) is that disruption is minimal. These techniques would maximise speed and minimise inconvenience of construction, helping to preserve existing communities and taking full advantage of the preexistence of all necessary infrastructure.
This makes room for niche developers that already specialise in custom built or pre-manufactured houses to grow into the market and work with local authorities and communities to continue the development of the different house types. This takes the onus of easing the housing crisis off large-scale speculative development, which often faces huge obstacles in terms of funding and community opposition, introducing a steadier stream of housing supply into the market. In addition, it champions the needs and characters of local communities and preserves the qualities that make London’s suburbs so popular, while combining them with the vibrancy and convenience of the city centre.
manufactured homes
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 pre-manufactured structural insulated panels (SIPS) is that disruption is minimal. These techniques would maximise speed and minimise inconvenience of construction, helping to preserve existing communities and taking full advantage of the preexistence of all necessary infrastructure.
This makes room for niche developers that already specialise in custom built or pre-manufactured houses to grow into the market and work with local authorities and communities to continue the development of the different house types. This takes the onus of easing the housing crisis off large-scale speculative development, which often faces huge obstacles in terms of funding and community opposition, introducing a steadier stream of housing supply into the market. In addition, it champions the needs and characters of local communities and preserves the qualities that make London’s suburbs so popular, while combining them with the vibrancy and convenience of the city centre.
Conclusion
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-lead approach, based on Local Development Orders and prior approval of plot passports would guarantee a high quality outcome.
We recommend pilot studies, located in the hinterland of large scale urban regeneration schemes in London that 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 NIMBY’s into YIMBY’s (Yes – in my back yard!)
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-lead approach, based on Local Development Orders and prior approval of plot passports would guarantee a high quality outcome.
We recommend pilot studies, located in the hinterland of large scale urban regeneration schemes in London that 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 NIMBY’s into YIMBY’s (Yes – in my back yard!)
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