Outbuilding approval rate in Hillingdon

Hillingdon approved 81.0% of outbuilding applications, based on 2,670 decisions analysed.

Last updated: August 2026

81.0%

outbuilding approval rate

2,670

Outbuilding decisions

2,162

Approved

508

Refused

80.0%

Hillingdon overall

Outbuilding applications are approved at roughly the same rate as the Hillingdon average (80.0%).

How outbuilding compares in Hillingdon

Outbuilding (2,670 decided)

81.0%

Hillingdon all applications (30,835 decided)

80.0%

Planning a outbuilding in Hillingdon?

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Other project types in Hillingdon

Rear Extension (10,275 decided)

78.4%

Garage / Parking (7,631 decided)

81.9%

Dormer (4,969 decided)

79.3%

Side Extension (4,872 decided)

71.8%

Hip-to-Gable Conversion (2,310 decided)

84.0%

Extension (General) (2,013 decided)

83.8%

New Build (1,672 decided)

81.3%

Change of Use (Residential) (1,484 decided)

74.9%

Front Extension (1,075 decided)

66.2%

Wraparound Extension (1,020 decided)

76.8%

Flat Conversion (917 decided)

73.6%

Conservatory (878 decided)

82.5%

Loft Conversion (498 decided)

74.3%

Basement (477 decided)

85.7%

HMO (347 decided)

58.5%

Annex (130 decided)

42.3%

← All Hillingdon planning statistics

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