What type of planning application is most likely to be approved in Harrow?

Hip-to-Gable Conversion at 86.4% based on 66 decisions.

What is hardest to get planning permission for in Harrow?

Annex at 43.6% based on 78 decisions.

How do approval rates vary by project type in Harrow?

From 86.4% (Hip-to-Gable Conversion) to 43.6% (Annex). What you build matters as much as where you build it.

Most Common Planning Applications in Harrow

Not all planning applications are created equal. The gap between the highest and lowest approval project type in Harrow is 42.8% — that's the difference between near-certainty and a coin flip. What you build matters as much as where you build it.

22,151 real decisions·17 project types·Updated August 2026

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All 17 project types ranked

#	Type	Decisions	Approved	Refused	Rate
1	Hip-to-Gable Conversion	66	57	9	86.4%
2	Conservatory	588	475	113	80.8%
3	Outbuilding	1,794	1,413	381	78.8%
4	New Build	63	49	14	77.8%
5	Front Extension	1,922	1,486	436	77.3%
6	Extension (General)	923	708	215	76.7%
7	Garage / Parking	3,725	2,846	879	76.4%
8	Wraparound Extension	290	220	70	75.9%
9	Rear Extension	10,671	8,043	2,628	75.4%
10	Dormer	4,314	3,217	1,097	74.6%
11	Side Extension	4,286	3,157	1,129	73.7%
12	Loft Conversion	119	84	35	70.6%
13	Basement	268	187	81	69.8%
14	Flat Conversion	278	176	102	63.3%
15	Change of Use (Residential)	761	476	285	62.5%
16	HMO	304	169	135	55.6%
17	Annex	78	34	44	43.6%

See how this applies to your postcode →

These are council averages. Your property is specific.

A hip-to-gable conversion application has a 86.4% approval rate. Annex? Just 43.6%.
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What the data tells us

The range is massive: 43.6% to 86.4%. Choosing the right project type — or framing your application correctly — can dramatically affect outcomes.

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.

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

5,340 planning applications in Harrow 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 Harrow planning data

Nearby councils project type rankings

Methodology: Classifies 22,151 decisions in Harrow 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 Harrow Council's public planning portal, January 2020 to August 2026. Full methodology →