Planning permission in Harrow
Constraints: planning.data.gov.uk (ingested 2026-06-15) · Prices: HM Land Registry UK House Price Index, October 2025 · 150 sales in October 2025 · Open Government Licence
Planning in Harrow — the detail
Harrow is an outer-London borough defined by the contrast between its historic hilltop core and its Metro-land suburbs. Harrow on the Hill — the village, Harrow School and Roxeth — sits at the centre of a cluster of conservation areas, and across the borough's 27 conservation areas the protected set pieces run from Pinner High Street and the Pinnerwood and Waxwell estates to Canons Park, Stanmore Hill, Roxborough Park and the Grimsdyke Estate. Inside these areas, design control on rooflines, materials and frontages is close, and permitted development is curtailed.
Harrow applies Article 4 directions within its conservation areas, removing permitted development rights so that even minor external alterations there need a planning application. The borough's detailed design rules for householder work live in its Residential Design Guide SPD, which incorporates the council's “Extensions: A Householder's Guide” and sets expectations on scale, materials, daylight and neighbour impact for extensions, alterations and conversions; the council also publishes prior-approval guidance for larger single-storey rear extensions.
Outside the conservation areas, Harrow's interwar semi-detached and Edwardian stock — on generous plots with side access — is strong territory for rear extensions, side extensions and loft conversions, much of it under permitted development or prior approval. As ever, the address-level check is what separates a permitted-development project from a full application in one of the conservation areas.
Policy detail lives in the Harrow local plan and applications are submitted via the Harrow planning portal.
Conservation areas in Harrow
Real · planning.data.gov.ukEvery designated conservation area in Harrow from the official dataset — inside one, permitted development narrows and design scrutiny rises.
- Canons Park Estate Conservation Area
- East End Farm Conservation Area Pinner
- Harrow on the Hill Village Conservation Area
- Harrow Park Conservation Area
- Harrow School Conservation Area Harrow on the Hill
- Kerry Avenue Conservation Area
- Little Common Conservation Area, Stanmore
- Moss Lane Conservation Area Pinner
- Mount Park Estate Conservation Area Harrow on the
- Old Church Lane Conservation Area Stanmore
- Pinner High Street Conservation Area Pinner
- Pinner Hill Estate Conservation Area
- Pinnerwood Farm Conservation Area Pinner
- Pinnerwood Park Estate Conservation Area PART 1
- Pinnerwood Park Estate Conservation Area PART 2
- RAYNERS LANE
- Roxborough Park and The Grove Conservation Area
- Roxeth Hill Conservation Area Harrow on the Hill
- South Hill Avenue Conservation Area Harrow on the
- Stanmore Hill Conservation Area
- Sudbury Hill Conservation Area Harrow on the Hill
- The Grimsdyke Estate and Brookshill Conservation A
- Tookes Green Conservation Area Pinner
- Waxwell Close Conservation Area Pinner
- Waxwell Lane Conservation Area Pinner
- West Drive Conservation Area
- West Towers Conservation Area Pinner
Source: planning.data.gov.uk · Open Government Licence. Boundaries are checked at address level by the area report.
Article 4 directions in Harrow
Real · planning.data.gov.ukNo Article 4 geometry for Harrow appears in the national planning.data.gov.uk dataset, but the borough operates householder Article 4 directions within its conservation areas — removing permitted development rights so that even minor external alterations there need planning permission. Outside the conservation areas, normal PD rights generally apply; the borough's Residential Design Guide SPD sets the design expectations. Check the council's Article 4 register for the position at a specific address.
Source: planning.data.gov.uk · Open Government Licence. Checked at address level by the area report.
What gets built in Harrow
Interwar semis in Pinner, Stanmore and Kenton extend routinely under PD; the Harrow on the Hill and Pinner conservation areas need a full application.
Costs & planning route →Workable on the Edwardian terraces of Harrow and Wealdstone; the hilltop and Pinner conservation areas need a full application.
Costs & planning route →Strong on the interwar semis of Pinner, Stanmore and Kenton under PD; the Harrow on the Hill and Pinner conservation areas scrutinise dormer design.
Costs & planning route →Uncommon on the borough's generous-plot stock; a full application with structural and ground-condition evidence is expected, more so in the conservation areas.
Costs & planning route →Large suburban gardens in Pinner, Stanmore and Harrow Weald suit garden rooms under PD; the conservation areas can remove outbuilding rights — check the address.
Costs & planning route →Harrow postcode by postcode
HA1 centres on Harrow on the Hill — the Village, Harrow School and Harrow Park conservation areas, with Roxborough Park nearby. In…
Area report →HA5 is Pinner — the Pinner High Street, Moss Lane, Waxwell Lane and Pinnerwood Park Estate conservation areas, a remarkably intact…
Area report →HA7 is Stanmore — the Stanmore Hill, Old Church Lane and Little Common conservation areas and the Grimsdyke Estate on the wooded r…
Area report →HA2 covers South Harrow, Roxeth and the Rayners Lane conservation area — Metro-land suburbia at its most characteristic. Much of t…
Area report →HA3 runs from Wealdstone and Kenton up to Harrow Weald and the Grimsdyke ridge. Conservation coverage is lighter here than the hil…
Area report →Harrow planning, asked straight
Is my Harrow home in a conservation area?
Do Harrow's Article 4 directions affect my extension?
Do I need planning permission for a rear extension or loft in Harrow?
What does Harrow's Residential Design Guide SPD cover?
How do I check constraints for a Harrow address?
Related reading
Designated land edits the rulebook — here's the exact redline.
Read the guide →Four roof forms, four budgets — and one big conservation premium.
Read the guide →The size limits, the exceptions, and the postcode-level traps.
Read the guide →What applies at your address?
Borough-level rules only narrow it down. Enter a Harrow postcode for the live constraint check — conservation area, Article 4 and sold-price comparables, cited to source.
Planning Permission Checker provides planning and cost intelligence for early feasibility only. It is not legal, planning, valuation, architectural, structural, or surveying advice. All estimates are indicative and must be verified by qualified professionals before purchase, design, planning submission, or construction.
Cost estimates are indicative only — not a quotation. Final price depends on survey, specification, structure, access, party wall matters, VAT, professional fees, and contractor availability.
Planning outcomes are not guaranteed. Local planning authorities make final decisions.