Conversion approval rates range from 93.6% in Kensington and Chelsea to 22.2% in Barking and Dagenham; a 71 percentage point spread. The same building type in the same condition faces fundamentally different odds depending on borough. Inner West boroughs approve; outer East boroughs refuse.
How much does borough choice affect conversion approval?
Conversions are the most common small site development type in London — 5,498 decided applications over three years, 45.8% of all small site activity. Yet approval rates vary so widely between boroughs that the same scheme in a different postcode might as well be a different application entirely. What is driving this?
A 71 percentage point spread across London boroughs
The London-wide conversion approval rate sits at 54.0%. That number is meaningless.
Across 32 boroughs with 20 or more decided conversion applications, approval ranges from 93.6% in Kensington & Chelsea (n=78) to 22.2% in Barking & Dagenham (n=45). A standard deviation of 18.3 percentage points. For the same development type.
| Borough | Approval Rate | Applications |
|---|---|---|
| Kensington & Chelsea | 93.6% | 78 |
| Camden | 88.9% | 90 |
| Richmond | 84.2% | 57 |
| Westminster | 79.4% | 165 |
| Hackney | 75.0% | 48 |
| ... | ||
| Waltham Forest | 33.3% | 99 |
| Hounslow | 32.1% | 84 |
| Newham | 29.9% | 137 |
| Havering | 26.5% | 155 |
| Barking & Dagenham | 22.2% | 45 |
The top five boroughs paint a clear geographic picture. K&C at 93.6%. Camden at 88.9% (n=90). Richmond at 84.2% (n=57). Westminster at 79.4% (n=165). Hackney at 75.0% (n=48). All inner London, all west or central, all boroughs where the existing housing stock was built for conversion — Victorian and Edwardian terraces with established precedent for subdivision.
The bottom five are equally instructive. Barking & Dagenham at 22.2% (n=45). Havering at 26.5% (n=155). Newham at 29.9% (n=137). Hounslow at 32.1% (n=84). Waltham Forest at 33.3% (n=99). Outer boroughs, predominantly east, with housing stock that was never designed for flat conversion and planning cultures that actively resist it.
This is a 71 percentage point spread. Not between different development types. Not between conservation areas and open land. Between boroughs, for the same category of work.
The geographic gradient is remarkably clean. Inner West approves conversions. Outer East refuses them. There are exceptions — Hackney sits east of centre but approves at 75%, likely reflecting its Victorian stock and established conversion market — but the broad pattern holds across three years of data.
What it does not reflect, at least not straightforwardly, is design quality or density. Conversion schemes are architecturally constrained by the existing envelope. You are subdividing a building, not designing one from scratch. The scope for design failure is narrower than for new-build. Yet the approval spread is wider than for any other site type. Something else is operating.
The most plausible explanation is planning culture. Boroughs with decades of conversion precedent treat subdivision as a normal part of the housing market. Boroughs without that history treat it as a loss — of family housing, of streetscene character, of a building type they would rather preserve intact. Policy language often supports this: several outer boroughs have explicit protections against the loss of family-sized dwellings through conversion. But even where policy is similar, enforcement varies enormously.
Check the approval rate before you check the guide price
Consider a developer with £500,000 to deploy on a conversion opportunity. They are looking at two properties: a three-storey Victorian terrace in Richmond and a similar building in Hounslow. Both are in the same property market corridor. Both would yield 3-4 flats. Both require planning permission.
In Richmond, the baseline approval rate for conversions is 84.2%. In Hounslow, it is 32.1%. The buildings are functionally identical. The planning outcome is not.
The Richmond scheme, at 84%, is close to a formality. Invest in a competent architect, follow the permitted development parameters where available, and you are overwhelmingly likely to get consent. The risk premium on acquisition should be low.
The Hounslow scheme, at 32%, is a speculative bet. Two in three applications fail. Even with strong design and pre-application engagement, you are fighting a planning culture that views conversion as undesirable. The risk premium on acquisition should be high — and for most developers, it should price the opportunity out entirely.
This is not an argument to avoid outer boroughs. It is an argument to check the conversion approval rate before you check the guide price. A developer who buys a conversion opportunity in a 30% borough at a 5% discount has made a worse bet than one who pays full price in an 80% borough. The planning risk dwarfs the acquisition saving.
What borough-level rates cannot tell you
Approval rates are not predictions. A 94% borough rate does not mean your scheme has a 94% chance — it means historically, the typical conversion application in that borough has been approved at that rate. Individual schemes vary with design quality, unit count, policy compliance, and the specific officer assigned. This analysis also cannot distinguish between full conversions and partial conversions, or between change-of-use applications and those proposing physical works. Some boroughs may have higher refusal rates partly because they attract weaker applications.
Borough-level conversion approval rates, area profiles, officer patterns, and viability modelling for all 33 boroughs are available in the full intelligence reports.