Nicholas Boys Smith is the founder and chairman of Create Streets.
When it comes to building sufficient homes in London, the only thing people can agree upon is that it’s not working. Everything else is up for debate.
It is no secret that London and the South East does not have enough homes. The ratio of average house prices to income has doubled since 1998. This reduces disposable income as wages are squandered in rent or mortgages; it gums up the labour market as people are unable to move; it even hinders marriage and childbirth as the right homes with sufficient bedrooms are just not available. The consequences for our standard of living and economic prosperity are catastrophic.
However, conventional brownfield and greenfield sites can be slow and pricey. They need new infrastructure, new streets and a complex mesh of utility connections and pipelines. With high imposed taxes in cash and kind, right now many developments end up requiring financial assistance from Homes England. This creates an absurd paradox: paying suppliers to create homes in a supply constrained market.
Historically, one important way that towns increased their supply was by ‘growing up’, with their streets evolving over the decades and centuries from two to three to five or to even more storeys as demand increased. Well into the Eighteenth Century, for example, the north side of the Strand was two-storey cottages; it is now towers at nine or ten storeys.
This ‘growing up’ on existing streets has the huge advantage of not requiring new infrastructure or, at worst, only modest improvements to existing infrastructure. The pipes are already there.
We need to escape from our near total reliance on large, complex sites by making it much easier once more for streets to ‘grow up’ and intensify in ways that local residents find acceptable.
Here’s one example of how to do it using existing legislation which the next London mayor should promulgate and which any council in high demand parts of the country could and should adopt tomorrow. It allows us to create new bedrooms for almost no public cost whilst improving existing streets and generating value for homeowners.
Sound too good to be true? Well, Create Streets’s latest report, Lessons from London: how legalising housing can give birth to a bedroom bonanza, shows that this is not theory. It is actually happening on the ground.
Mansard roof extensions offer a modest but useful low-cost, way to increase living space on some streets. They can add around a quarter to a third more floorspace to Victorian and Georgian houses, often in central, well-connected locations, without harming neighbourhood character. Most create two new bedrooms and can be tucked elegantly and unobtrusively behind the parapet, with the construction cost being a fraction of the value of the space created.
In 2017, Tower Hamlets Council encouraged carefully design-coded mansard extensions in one neighbourhood just south of Victoria Park as part of updated Conservation Area character appraisal and management guidelines. The revised guidelines strongly encouraged mansard uplift and included a short visual design code setting out how to execute them well.
Planning permission is still required, though it is hard for the council to say no as long as the design code is followed. The success is dramatic. Average annual applications rose by 688 per cent and success rates at planning leapt from 27 per cent to 93 per cent. There are now in consequence around 300 extra bedrooms in Tower Hamlets which would not otherwise exist. And never forget, bedrooms matter as well as new ‘units’. More bedrooms in cities are associated with reduced homelessness.
Then in 2023, thanks to Create Streets, the last government amended national policy to back upward extensions where appearance harmonises with the original. It said that authorities should not require simultaneous development across a terrace. This has not yet a huge effect on applications. Not many people know about it.
But it has had a significant effect on success rates at appeal. Successful appeal to the Planning Inspectorate increased from 17 per cent in period before the policy change to 42 per cent afterwards. This will surely start to feed through to applications over time.
But councils can speed it up if they wish and ensure that new mansards fit in. Local councils can set clearer local policy in the spirit of the national guidance. The first of these of which I am aware is the Redcliffe Road Local Development Order (so-called LDO) in Kensington and Chelsea. This pre-grants planning approval as long as the mansard follows a set pattern thus totally eliminating planning risk. Literally nothing stops you as long as you follow the code.
Remarkably, within 18 months, five of the twelve eligible homes on Redcliffe Road have begun building mansards, confirming high latent demand when planning risk is removed. A sixth, I understand, is starting imminently. This LDO could, and I believe should, be extended much more widely across thousands of terraces in London and high demand areas of the country.
Policy implications are wide-ranging: London boroughs, the GLA, and national government could unlock tens of thousands of new bedrooms by adopting LDOs (as in RBKC) or Supplementary Planning Documents (as in Tower Hamlets) linked to template design codes for mansards. Counting additional bedrooms, not just new homes, would help us focus on the quickest ways to make a measurable, resilient contribution to tackling the housing crisis.
I don’t pretend for a moment that we can ‘solve’ our housing crisis by building more mansards. Set against the scale of the challenge the potential from new mansards is modest. But these examples do show how de-risking development in ways that are locally acceptable can rapidly diversify supply and create bedrooms. This, I would judge, is good Conservative policy as it re-empowers local homeowners and reduces the harm done by planning and regulation.
All boroughs in high demand areas should write this type of policy into their local plan. Based on the evidence Create Streets sets out in our report I predict with high confidence that were they do so, they would increase the supply of bedrooms at zero political risk, to the enrichment of individual homeowners and at almost no cost to the public purse.
There are no real ‘easy wins’ in life but this is as near as you can reasonably expect.
