Nicholas Boys Smith sets out how Create Streets’ latest report presents an opportunity to London’s councils
Nicholas Boys Smith sets out how Create Streets’ latest report presents an opportunity to London’s councils
Can we create new bedrooms for almost no public cost whilst improving existing streets, generating value for homeowners and supporting sustainable development patterns?
Yes, we can. Does it sound too good to be true? Well, Create Street’s latest report, Lessons from London: how legalising housing can give birth to a bedroom bonanza, shows it actually happening on the ground. There’s a real and actionable opportunity here for London’s councils if there are prepared to ‘bring the democracy forward’ and pre-define and de-risk mansard extensions following a pre-approved design code which local people will accept.
Mansard roof extensions offer a modest but useful low-cost, low-carbon 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.
Evidence from Tower Hamlets shows the impact of clear design codes: after the council introduced guidance supporting mansards, applications rose nearly sevenfold and success rates leapt from 27% to 93%, leading to around 300 extra bedrooms. Bedrooms matter as well as new ‘units’. More bedrooms are correlated with reduced homelessness.
Then In 2023, thanks to Create Streets, national policy was amended 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% in period before the policy change to 42% afterwards.
It also provides an opportunity for local councils to set ever clearer local policy in the spirit of the national guidance. The first that we are aware of is the Redcliffe Road Local Development Order (a so-called LDO) in Kensington & Chelsea. This demonstrates the power of pre-approved design frameworks using an existing legal mechanism, the LDO. For remarkably, within 18 months, five of the twelve eligible homes on Redcliffe Road had begun building mansards, confirming high latent demand when planning risk is removed. A sixth we, understand, is starting imminently. This LDO could, and we believe should, be extended much more widely.
Policy implications are wide-ranging: London boroughs, the GLA, and national government could unlock tens of thousands of new bedrooms by adopting LDOs or SPDs 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, energy-efficient contribution to tackling the housing crisis.
We 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 they do show how de-risking development in ways that are locally politically acceptable can rapidly diversify supply and create bedrooms.
All London boroughs should write this type of policy into their local plan or associated SPDs. Based on the evidence we set out in our report I think we can predict with high confidence that were they do so that would increase the supply of bedrooms in London at no political cost, to the enrichment of individual homeowners (not the aim but no bad thing) and at almost no cost to the public purse.
I am not a believer in ‘easy wins’ but this is as near as you get to one.
Nicholas Boys Smith sets out how Create Streets’ latest report presents an opportunity to London’s councils