Data-backed planning intelligence · 3,290,000+ decisions analysed across England

Most Common Planning Applications in Cardiff

Not all planning applications are created equal. The gap between the highest and lowest approval project type in Cardiff is 39.1% — that's the difference between near-certainty and a coin flip. What you build matters as much as where you build it.

4,803 real decisions·15 project types·Updated June 2026
88.5%
Safest: Flat Conversion
49.4%
Lowest: Conservatory
39.1%
Spread
15
Types ranked

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All 15 project types ranked

#TypeDecisionsApprovedRefusedRate
1Flat Conversion26233
88.5%
2Dormer21618531
85.6%
3Hip-to-Gable Conversion635310
84.1%
4Front Extension24204
83.3%
5HMO29245
82.8%
6Annex28226
78.6%
7Outbuilding816318
77.8%
8New Build21156
71.4%
9Loft Conversion20514461
70.2%
10Rear Extension364247117
67.9%
11Garage / Parking29319697
66.9%
12Extension (General)29319598
66.6%
13Side Extension15410153
65.6%
14Change of Use (Residential)895336
59.6%
15Conservatory1768789
49.4%
See how this applies to your postcode →

These are council averages. Your property is specific.

A flat conversion application has a 88.5% approval rate. Conservatory? Just 49.4%.
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What the data tells us

1
The range is massive: 49.4% to 88.5%. Choosing the right project type — or framing your application correctly — can dramatically affect outcomes.
2
Visibility drives scrutiny. Project types that change the external appearance — dormers, loft conversions, hip-to-gable — face more resistance than those that don't. The more visible your proposal, the more carefully it needs designing.
3
These are council-wide averages. Your ward, your street and your immediate neighbours all shift the odds. The comparable decisions near your property are the best indicator of outcome.

Before you spend £5,000+ on architects and drawings

877 planning 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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More Cardiff planning data

Methodology: Classifies 4,803 decisions in Cardiff into residential project types using keyword matching against proposal descriptions (matching generate_site_data.py subtype rules). A single application may appear in multiple categories. Data from Cardiff Council's public planning portal, January 2020 to present. Full methodology →
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