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Does planning permission actually add value?
19,179 properties in England and Wales sold, then got permission, then sold again. Comparing what happened to those prices against what happened to prices generally in the same postcode district over the same years.
| Work | Properties | Their sale rose | Their district rose | Net difference | Beat the district |
|---|---|---|---|---|---|
| Extension | 17,182 | +62% | +34.4% | +14.1% middle half -4.4% to +37.3% | 69.2% |
| Loft conversion | 1,469 | +54.4% | +30.9% | +9.8% middle half -7.9% to +33.3% | 64.3% |
| Outbuilding or annexe | 528 | +58.9% | +32.4% | +9.7% middle half -5.1% to +29.1% | 66.7% |
What this does and does not show
The net difference is calculated per property — each sale's growth divided by its own district's growth over the same two years — and then the median of those. It is not the difference between the two column averages, which would be a much cruder number.
This is association, not proof. People extend houses they were already improving; the register records neither the works nor what they cost, so some of this gap is the extension and some is everything else done at the same time. The spread matters as much as the middle: for extensions the middle half of properties land between -4.4% and +37.3%, and roughly three in ten did worse than their district despite having permission.
Permission is matched to an address by full postcode plus house number — the same conservative key used everywhere on this site — so a neighbour's permission is never credited to your sale. Bulk and nominal transfers are excluded. Coverage follows the planning data: London in full plus the councils that publish openly.