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Most Common Planning Applications in Hillingdon

Not all planning applications are created equal. The gap between the highest and lowest approval project type in Hillingdon is 43.3% — that's the difference between near-certainty and a coin flip. What you build matters as much as where you build it.

30,009 real decisions·17 project types·Updated March 2026
84.1%
Safest: Basement
40.8%
Lowest: Annex
43.3%
Spread
17
Types ranked

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All 17 project types ranked

#TypeDecisionsApprovedRefusedRate
1Basement47840276
84.1%
2Hip-to-Gable Conversion2,2381,870368
83.6%
3Extension (General)1,9571,624333
83.0%
4Conservatory832681151
81.9%
5Garage / Parking7,5476,1051,442
80.9%
6New Build1,6441,315329
80.0%
7Outbuilding2,5722,058514
80.0%
8Dormer4,8303,7861,044
78.4%
9Rear Extension9,9307,7012,229
77.6%
10Wraparound Extension947718229
75.8%
11Change of Use (Residential)1,4391,077362
74.8%
12Loft Conversion475350125
73.7%
13Flat Conversion914667247
73.0%
14Side Extension4,7673,3781,389
70.9%
15Front Extension1,057692365
65.5%
16HMO319190129
59.6%
17Annex1255174
40.8%
See how this applies to your postcode →

These are council averages. Your property is specific.

A basement application has a 84.1% approval rate. Annex? Just 40.8%.
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What the data tells us

1
The range is massive: 40.8% to 84.1%. 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

6,346 planning applications in Hillingdon have been refused since 2020. Many of those homeowners had already paid for drawings and application fees. A £79 report shows you what gets approved — and what gets refused — near your property.

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More Hillingdon planning data

Nearby councils project type rankings

Methodology: Classifies 30,009 decisions in Hillingdon 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 Hillingdon Council's public planning portal, January 2020 to present. Full methodology →
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