Rear extensions are the bread and butter of UK planning — and one of the most common reasons homeowners face a refusal. Here's what 467 real decisions tell us about rear extension outcomes in Cardiff.
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Rear extensions sit in the middle of the pack nationally. They're common enough that councils have clear precedent — but that cuts both ways. If your neighbours have been refused, that precedent works against you too.
Two houses on the same street can get different outcomes.
Check your postcode to see what actually happens near your address.
Not all applications are treated equally. Here's how rear extensions stack up against other common projects in Cardiff.
| Type | Decisions | Rate |
|---|---|---|
| Flat Conversion | 28 | 89.3% |
| Front Extension | 36 | 86.1% |
| Wraparound Extension | 26 | 84.6% |
| Dormer | 275 | 84.0% |
| Hip-to-Gable Conversion | 81 | 84.0% |
| HMO | 50 | 80.0% |
| Annex | 32 | 78.1% |
| Outbuilding | 96 | 77.1% |
| New Build | 24 | 75.0% |
| Rear Extension | 467 | 72.8% |
| Loft Conversion | 252 | 72.2% |
| Side Extension | 208 | 72.1% |
| Garage / Parking | 332 | 68.7% |
| Extension (General) | 315 | 67.9% |
| Change of Use (Residential) | 118 | 66.9% |
| Conservatory | 187 | 52.4% |
127 rear extension applications in Cardiff have been refused since 2020. Many of those homeowners had already paid for drawings and application fees. A free, property-specific report shows you what gets approved — and what gets refused — near your property.
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