Building work in Harrow: area guide

Harrow Council is the planning and building control authority for Harrow, which covers HA1, HA2, HA3, HA5, HA7 and HA8 and takes in Pinner and Stanmore. This is our area guide to building work in the borough; for whole-house refurbishment go to Home renovation in Harrow.

Harrow counts roughly 96,870 homes for Council Tax; 10% are older than 1919, 52% interwar and 38% post-war, with 38% flats and 62% houses. VOA Council Tax stock of properties, March 2025, for all 30 statistical areas in Harrow. Counts rounded by the VOA.

Planning and building control in Harrow

What Harrow Council publishes about building work in the borough, with each point linked to the council page it comes from:

• Harrow Council's conservation page states that Harrow has 30 Conservation Areas. harrow.gov.uk
• Harrow's immediate Article 4 Direction on small HMOs means any new small HMO created on or after 12 June 2026 requires planning permission. harrow.gov.uk
• Harrow's Conservation Areas Residential Planning Guidelines say Article 4 Directions can mean planning permission is needed to replace doors and windows, for any hardsurfacing, and for boundary walls and fences. harrow.gov.uk
• Harrow Council states that there are around 372,905 listed building entries in England, over 300 of which are in Harrow. harrow.gov.uk
• Harrow's householder pre-application advice costs £530.80 including VAT for a meeting and written response, or £324.40 for a written response only. harrow.gov.uk
• Harrow Council runs its own building control service, and says you might need Building Control approval from the council if you want to build in Harrow. harrow.gov.uk
• Harrow Building Control publishes separate application forms for full plans, building notice and regularisation applications. harrow.gov.uk
• On Harrow full plans, building notice and regularisation applications the applicant must submit a completion notice under Regulation 16(4a), or the completion certificate is withheld. harrow.gov.uk
• Harrow Local Plan Policy GR4A supports basements for ancillary accommodation only where they do not extend into the rear garden more than 50% of the depth of the host dwelling. harrow.gov.uk

62% of Harrow's homes are houses, which keep householder permitted development: a single-storey rear extension within the size limits can usually go ahead without an application, in a conservation area too unless an Article 4 direction removes it. The 38% that are flats have no householder permitted development, so their extensions and most external changes need planning permission from Harrow Council. Taking out a wall or a chimney breast is building regulations work, not planning, unless the building is listed.

Harrow is Metroland at its most complete. Pinner, Stanmore, Rayners Lane and the streets across HA1, HA2, HA3, HA5, HA7 and HA8 were built out between the wars along the railway: mock-Tudor semis with applied timbering, gabled fronts, tile hanging, leaded lights and rendered upper storeys. That style decides most jobs here, because matching it is what separates a sympathetic house extension scheme from one that makes a whole street look wrong.

Mock-Tudor detailing comes before the extension

The decorative elements on these houses are not structural, but they are what the street looks like: applied timber boards on a rendered background, plain clay tile hanging to the first floor, leaded casement windows and a projecting front gable. Matching them on an extension matters more than on a plain brick terrace, while opening the kitchen through the back wall is RSJ installation work that leaves the front untouched.

That means sourcing tiles that weather in alongside the originals, reproducing timber and render detail on new gables, and keeping window proportions consistent where glazing is upgraded. Harrow Council has designated conservation areas including parts of Pinner and Harrow on the Hill. Inside those, side and roof additions need planning permission and materials face direct scrutiny.

Interwar semis and post-war homes: the spine wall and the roof above it

Behind the mock-Tudor front, the typical Harrow semi is a cavity-walled house with a hipped cut roof, a spine wall between the front and back rooms and often a garage to one side. Joining the back rooms means taking out a wall that carries the first floor and sometimes a roof strut landing on the wall above, so it is load-bearing wall removal: the structural engineer we appoint checks the loft before sizing the beam, and the cavity is closed and both leaves supported at the bearings.

Nearly two in five Harrow homes were built after 1945, many of them flats. A post-war house may have a trussed roof and a concrete ground floor, which makes an opening simpler to design but a floor harder to chase, and a flat routes first through the freeholder's licence rather than planning. Harrow Council building control, or a registered building control approver, inspects the steel, the foundations of any extension and the drainage before they are covered.

Popular starting points in Harrow: kitchen renovation in Harrow, house extensions across Harrow, builders in London and Renovation Mistakes to Avoid.