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 42.1% based on 76 decisions.

How do approval rates vary by project type in Harrow?

From 86.4% (Hip-to-Gable Conversion) to 42.1% (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 44.3% — that's the difference between near-certainty and a coin flip. What you build matters as much as where you build it.

21,804 real decisions·17 project types·Updated June 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	582	472	110	81.1%
3	Outbuilding	1,769	1,397	372	79.0%
4	New Build	61	48	13	78.7%
5	Front Extension	1,890	1,462	428	77.4%
6	Extension (General)	908	700	208	77.1%
7	Garage / Parking	3,654	2,789	865	76.3%
8	Wraparound Extension	286	216	70	75.5%
9	Rear Extension	10,512	7,911	2,601	75.3%
10	Dormer	4,257	3,175	1,082	74.6%
11	Side Extension	4,224	3,110	1,114	73.6%
12	Loft Conversion	117	82	35	70.1%
13	Basement	267	186	81	69.7%
14	Change of Use (Residential)	739	469	270	63.5%
15	Flat Conversion	274	173	101	63.1%
16	HMO	287	162	125	56.4%
17	Annex	76	32	44	42.1%

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 42.1%.
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What the data tells us

The range is massive: 42.1% 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

5,255 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 21,804 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 present. Full methodology →