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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 36.9% — that's the difference between near-certainty and a coin flip. What you build matters as much as where you build it.

5,184 real decisions·16 project types·Updated August 2026
89.3%
Safest: Flat Conversion
52.4%
Lowest: Conservatory
36.9%
Spread
16
Types ranked

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All 16 project types ranked

#TypeDecisionsApprovedRefusedRate
1Flat Conversion28253
89.3%
2Front Extension36315
86.1%
3Wraparound Extension26224
84.6%
4Dormer27523144
84.0%
5Hip-to-Gable Conversion816813
84.0%
6HMO504010
80.0%
7Annex32257
78.1%
8Outbuilding967422
77.1%
9New Build24186
75.0%
10Rear Extension467340127
72.8%
11Loft Conversion25218270
72.2%
12Side Extension20815058
72.1%
13Garage / Parking332228104
68.7%
14Extension (General)315214101
67.9%
15Change of Use (Residential)1187939
66.9%
16Conservatory1879889
52.4%
See how this applies to your postcode →

These are council averages. Your property is specific.

A flat conversion application has a 89.3% approval rate. Conservatory? Just 52.4%.
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What the data tells us

1
The range is massive: 52.4% to 89.3%. 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

910 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 5,184 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 August 2026. Full methodology →
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