
Table of Contents
Summary
Homebuilding is critical to the new government’s mission for growth. Every 100,000 additional homes will add a total of around 1% to GDP over the period they are built.
However, some of the most ambitious initiatives like New Towns, and fundamental reform of the planning system, will take more time to start delivering homes.
This briefing describes three ‘fast wins’ on housing which can be delivered in the first 100 days of government and boost housing supply in the short-medium term, without requiring more resourcing from central government.
The three proposals could create approximately 30,000 new homes per year through ‘infill’ development, building more homes at gentle densities of terraced houses and mansion blocks.
Building up: learning from Haringey to set policy for sympathetic upward extensions, adding more living space and new homes.
Street votes: completing the implementation of street votes would allow communities to bring forward development through local decision making.
Estate renewal: amending national policy to catalyse estate renewal. This will make it easier for social landlords to deliver better homes for tenants. Cross-subsidy from new market homes could pay for new council homes for existing tenants and also net new council homes.
To increase growth, we need to enable the full potential of people living and working near each other, allowing the most productive firms to grow and create more good jobs. That means it is critical to build more homes in the places with the highest productivity.
Another benefit is that infill sites provide valuable opportunities for small and medium sized builders, creating jobs and economic activity.
If done without care, infill can be controversial. Developer-led schemes that produce incongruous buildings can be highly unpopular. These three proposals are careful and impactful, sensitive to the needs and preferences of local areas.
The new government’s intention to build with high-quality ‘gentle density’ has proven highly popular. Labour’s manifesto also committed to prioritising the development of previously used (‘brownfield’) land, including in urban areas.
Because infill focuses on areas of high land values and greater housing shortage, it will deliver a greater economic impact than the average new home. In every year that they are sustained, these policies should generate an additional 0.5% of GDP in every year and an additional £1 billion of revenues to HM Treasury.
The Challenge
Ambitious measures like New Towns can be highly successful, as shown by Milton Keynes. But site selection, planning, Environmental Impact Assessments, and building infrastructure generally mean it will take considerable time before any new homes can be built.
Targeted planning for more homes on greenfield sites is likely to be a faster way to enable more development, although many of those come with infrastructure requirements of their own, which will also take time.
The homebuilding sector is in crisis. If output collapses – as on current trends it will – skills and capacity will atrophy, making it much harder to deliver a housing boom later on. The Government needs measures that can ramp up housebuilding immediately, without having to wait for new infrastructure.
As well as helping with speed of delivery, infill can also help with the problem of delivering enough new homes per year. Even 300,000 homes a year are unlikely to be sufficient to keep up with demand and boost growth, unless considerably more homes are built in the highest demand areas. At the per capita rates achieved in the 1930s, the UK would be building 750,00 homes per year. Bidwells estimates that the UK needs to build 550,000 homes a year for ten years to catch up.
Infill can deliver this. We can add homes around existing public transport infrastructure and high streets much faster than we can build new transport systems to new sites.
The challenge is to ensure new homes are popular and supported by local communities. Otherwise, there may be a backlash. Over time, various proposals for densification in existing settlements have met with energetic resistance. For this reason, smart planning is needed to ensure the support of local communities for new homes near them.
The Opportunity
Infill: speed and growth
Around the world, affordable housing campaigners are focused on ‘infill’ development in existing urban areas near to public transport because it has a proven ability to deliver large additional numbers of new homes, quickly. Enabling new homes from many different builders on smaller sites will deliver faster than relying solely on developers of large sites who will build only at their local ‘absorption rate’.
Infill also generates the largest ‘agglomeration effects’ because it means the new residents have to travel less far to other people and amenities. Labour’s 2023 housing announcement showed its understanding of the need to prioritise homes in the areas of very high housing need and close to transport hubs.
Infill is most likely to be viable in areas with high land values and severe housing shortages. Land values are generally high because those places offer access to the best-paid jobs at the most productive firms. Building more homes near those firms allows them to grow rapidly by creating more high wage jobs. That means they, and their workers, in turn earn more and pay more tax, allowing improvements in public services. Homes generated through infill in productive urban areas will generate the most growth and fiscal benefits.
Economists Gilles Duranton and Diego Puga estimated that adding more homes in just seven of the most productive US cities would raise U.S. output per person by 7.95%. An Institute for Fiscal Studies report found that the average UK worker moving from the least to the most productive area sees a wage increase of 17%. President Biden’s administration made clear the importance of supplying homes in high productivity cities to enable higher wages.
A wave of progressive governments around the world have passed reforms to enable more homes in existing settlements.
In the US, various states including California have had substantial success with highly popular reforms to allow homeowners to add auxiliary dwelling units – ‘granny flats’ or ‘granny cottages’. Such reforms have probably been the most impactful reform in California to increase the supply of new homes: permissions for ADUs soared from roughly 1000 a year in 2016 to roughly 25,000 a year in 2022. As of 2022, 19% of all new homes produced in California were ADUs. And the effect has been most pronounced in less affordable cities like Los Angeles, where the number of permits issued went from 80 in 2016 to 7,160 in 2022.
In New Zealand, Auckland planning rules were amended to allow more new homes through infill development. Permits for new housing roughly doubled within five years.
Similar benefits from rules to allow more gentle density have been seen in Minneapolis and Houston. Houston’s Democrat local government changed the rules to permit more homes per acre, but allowed smaller areas to ‘opt out’ to ensure that the rules were not contentious. Western Australia’s Labor government recently changed the rules to permit ‘granny flats’ of up to 70 square metres. In Canada, Justin Trudeau’s government has offered additional federal funding to cities which remove their ban on four-apartment buildings in suburban areas.
Infill can make better use of existing infrastructure, which can be upgraded organically over time. Additional passengers for local public transport can make better and more frequent services viable and help struggling high streets. Because such infill generally only needs small upgrades to existing utilities, it should pay for itself, while boosting tax revenues by permitting high-productivity firms to expand by hiring the new workers who move into those homes.
Providing access to good jobs and training in the UK’s towns and cities is key for national economic growth. Urban areas are 21% more productive than other areas and are home to 72% of the UK’s highly skilled jobs. The lack of affordable homes in cities is a key barrier to opportunity, reducing overall wages and leaving less income after housing costs.
Many towns and cities are incubators of high-growth firms, keen to hire and train more workers. To unlock the potential of people and communities around the country, we need to let those firms grow, training up workers who can then start businesses of their own.
TUC research on commuting times shows Britain’s workers have the longest commutes in Western Europe and that these are longest in the metro areas of the most unaffordable cities. Many homes are currently underserved by public transport. The low housing densities of English cities have made the situation even more challenging by limiting the viability of good public transport. Long commutes have severe human, economic and environmental costs.
As well as improving quality of life for workers, infill also has enormous environmental benefits compared to additional sprawl. First, infill requires much less additional infrastructure, with all the accompanying embedded carbon. People living outside cities emit 50% more carbon emissions than those in cities. This is because they are content with more compact homes with less embedded carbon, in return for the greater range of amenities in cities; because they are more likely to use public transport than rely on cars; and because they are more likely to live in terraced housing or flats, which are better insulated than detached houses.
Adding more homes in existing urban neighbourhoods also makes it viable to improve the frequency of existing public transport in a ‘virtuous circle’. This helps to reduce carbon emissions further.
Infill can be popular
Many UK cities have large areas of lower housing density. Many of the residents would be keen to do more with their properties. Ballots for estate renewal in London show that many social tenants are keen for better living conditions and happy to support careful estate renewal if it will give them and their families a better life. With the right policies, there is plenty of scope to add more housing in those places. But those policies must ensure the maximum possible local support. In particular, they must take care to enhance, not harm, historic areas.
There was broad popular support for the design-led ‘gentle density’ set out in the new government’s vision for New Towns and other housing. Infill is a key part of development on brownfield, which is defined as previously used land, including urban areas. The new government has committed to taking a ‘brownfield first’ approach and to fast-tracking approval of urban brownfield sites.
Figure 1: Impressions of the new Government’s proposed ‘gentle density’ provoked great popular interest.

Source: Create Streets
There are three things in particular that the Government could do to enable popular infill development.
1. Learn from Haringey
The Labour-led local authority in South Tottenham, Haringey, successfully worked with the community to write a Supplementary Planning Document to allow harmonious upward extension of Victorian and Edwardian houses. Both the initial and follow-up consultations showed strong support for the policy. In 2017, Tower Hamlets introduced a policy to allow sympathetic upward extensions in the form of mansard roofs.
A Written Ministerial Statement could create the basis for such policy nationwide within the first 100 days of the next government. That could be followed with an NDMP to give the policy additional strength. To ensure popular support, such policy should only apply where there is strong support in the local area.
Figure 2: Houses harmoniously expanded using the Haringey policy.

Upward extensions can deliver over 100,000 homes in the right places for British workers, and improve family homes with additional living space and bedrooms. The additional bedrooms can also help to mitigate the housing problem in unaffordable places. Many families are stuck in overcrowded conditions and desperately need more room. Uptake on upward extensions in Tottenham has been high. Over 200 of the around 1,000 homes eligible have already chosen to extend their property.
2. Street votes
The ‘opt-out’ system in Houston, described above, has allowed substantial intensification without backlash. Street votes are designed to achieve the same benefits, building on the Greater London Authority’s Supurbia proposals for sensitive suburban intensification. The proposal has won widespread support from centre-left figures including Nicky Gavron, Toby Lloyd, Jamie Ratcliff, Geeta Nanda, Russell Curtis of RCKa, Dan Wilson Craw of Generation Rent; from Sally Copley of Sustrans, Peter Eversden MBE, the Chair of the London Forum of Amenity and Civic Societies, Nicholas Boys Smith, and Richard Blyth of the Royal Town Planning Institute; and from respected advocates of pro-growth policy including Tony Travers, ESRC Chair Stian Westlake, and John Fingleton CBE.
Street votes would let small local communities set out additional forms of additional housing that may be permitted, with extensive safeguards to protect historic properties and residents on other streets.
Schemes in Vancouver, Seoul and Tel Aviv, together with the high majorities in support of tenant ballots in London, demonstrate that some residents will support more local development when they see strong benefits for them and their families.
Street votes may just permit extensions or ‘granny flats’ . But the lessons of other countries is that a small fraction of streets may have sufficient ambition to replace run-down semi-detached houses with terraced housing or mansion blocks, which can offer up to ten times as many homes on the original site. Indeed, one building designed by Peter Barber on Hafer Road in London gives an example of ambitious replacement, albeit without the protections for other residents that street votes would offer. Most residents may not be interested. But it will only require takeup by a few percent of streets to deliver 25,000 new homes per year in the highest demand areas like London or Cambridge.
The Department has already consulted and done extensive further work on the implementation of street votes, which could be brought into force within 100 days.
Unlike the normal community infrastructure levy (CIL) regime, councils will be able to use CIL revenues from street vote development to build new council homes.
International examples in South Korea, Israel, Vancouver and Houston show that street votes could deliver over 20,000 homes per year within the first three years, in addition to the homes that would come through regular planning processes. Those homes will be driven by communities themselves. Critically, this would be mainly in places like London where the housing shortage is greatest.
Figure 3: Before and after potential infill through street votes

It will take longer to boost estate renewal. Where projects go beyond simple conversion of garages into new homes and seek to replace existing homes, they can take a decade to complete. But creating a better framework to make renewal easier for social landlords will give them the confidence to start working on it now and accelerate current renewal proposals. Over time, careful estate renewal could deliver over 300,000 additional homes, including new council homes, where they are most needed.
3. Estate renewal
Estate renewal, where done carefully and well, has also proved popular. Since the Labour Mayor of London imposed a requirement for tenants ballots to approve estate renewal, 31 ballots have passed – all but one of them on the first proposal. Tenants generally welcome better insulated and bigger homes to replace buildings that are past their design life.
In some of the most unaffordable areas, the prices of market homes vastly exceed economic construction costs. That means that sufficiently ambitious renewal proposals can fund new council homes for every existing resident through cross-subsidies from building market homes, and even deliver additional council homes to help tackle long waiting lists. By their nature, those sites are in the areas of highest demand, where building more homes will do the most for growth. In other areas, such cross-subsidy will allow retrofitting with better insulation and more efficient heating and ventilation.
But social landlords face enormous challenges in delivering estate renewal. Grants often must be spent within a few years, making them ill-suited for renewal projects which may last more than a decade. Utilities and transport providers can be uncooperative. Most councils no longer have the in-house expertise to plan and manage regeneration. And national policies and building regulations can change every year, so a proposal which was viable at the beginning may become unviable after those changes.
Figure 4: Estate renewal - before and after in South Kilburn. In the ballot, 84% were in favour.

The Potential
These three infill policies alone have the potential to enable 30,000 new homes a year.
Building new homes through these processes will be most viable in areas with high land prices. That means it will add much needed supply in the most unaffordable areas, which means it will do the most to drive growth and improve the fiscal position.
Plan of Action
Upward extensions of older properties
The Government should create national policy stating that the new local design codes being adopted by every local authority should set out how harmonious upward house extensions may be permitted. The policy should include a presumption in favour of a proposed upward extension that is harmonious with the existing building, if the application is made or supported by a majority of nearby residents, wherever a joint application is made by or supported by a majority of the nearby residents.
The policy should include requirements to improve energy efficiency by adding insulation to roofs and retrofitting other parts of the building, helping with the climate crisis.
Street votes
The Government should instruct the Department to proceed at pace with the implementation of the street votes proposals that it has worked up. A milder version of the policy for areas with older housing can be prepared in due course, but it is important to ensure that there are no negative effects and to monitor the initial phase with those areas excluded. For that reason, the proposal in the Department’s consultation that street votes would be permitted in conservation areas should be postponed for a later time.
Estate renewal
The Government should instruct the Department to create a new, stronger policy presumption via Written Ministerial Statement or through the NPPF, and reinforced through a subsequent National Development Management Policy. The presumption should apply in favour of estate renewal where that renewal will not have significant overall adverse effects on the communities surrounding the estate.
FAQs
What will this cost?
None of the above proposals should have any net cost to the Treasury. Amending national policy in favour of estate renewal will not incur any new fiscal commitments. Estate renewal without additional funding should be possible in many places by reprofiling the existing grants, and in parts of central London it may be possible for it to be entirely self-funding. By enabling additional development where it will create the most value, these proposals should boost growth and help the overall fiscal position. Apart from the additional officer time to process the applications, community-driven processes like upward extensions and street votes have no additional cost, even in the short term.
Are there any international comparisons?
Infill has a strong track record of success in a range of places including Auckland, Houston, California, and Minneapolis. Community-led development has been successful in many places including London, Vancouver, Tel Aviv and South Korea.
Will any of these proposals cause negative effects?
Design codes for upward extension and a requirement that they be harmonious, like those in South Tottenham, should ensure that the development does not harm the street. Similarly, street votes are designed to ensure that there are no significant negative effects on neighbours on other streets, while the additional CIL revenues will allow local authorities to build more infrastructure and council homes. The ballots have shown that estate renewal is often overwhelmingly welcomed by tenants because of the better living conditions that it will bring for them and their families.
Will any of these proposals interfere with current planning practices?
Design codes for upward extension are a simple extension of current planning practices. Those codes should provide clarity to make it easy for officers to decide upon them under delegated powers. Street votes are designed purely as a supplementary route to allow development that will not interfere in any way with existing planning applications, and cannot reduce the volume of housing built. Providing clearer rules for estate renewal should also reduce the overall planning burden.
Won't upward extensions and street votes just help existing homeowners?
International examples, including ADUs in California and the rule changes in Auckland, show that infill can create new homes as well as just larger homes. But even extensions of overcrowded homes can help the rest of the community. For example, it can let elderly relatives or adult children stay in the family home, leaving another home free for others. And sometimes larger homes can be subdivided to create two or more new homes, as seen in much of the Victorian stock in high demand cities like London.
Kane Emerson is Head of Housing Research at YIMBY Alliance, founder of Labour YIMBY and a former aide to Emily Thornberry MP. Kane is also Vice-Chair of Islington South CLP and Treasurer of Labour Party Irish Society.
John Myers is Director of YIMBY Alliance and longstanding campaigner for an end to the housing crisis. He is a former competition lawyer and analyst.