Loft conversion with skylights in an inter-war semi in North Harrow HA2, London Borough of Harrow

North Harrow and Rayners Lane · HA2 · Harrow

House Extension Drawings in North Harrow and Rayners Lane HA2

Fixed-fee, MCIAT-chartered house extension drawings for North Harrow and Rayners Lane (HA2) homeowners — London Borough of Harrow validation and local constraints handled from the start.

HA2 covers North Harrow, Rayners Lane, West Harrow and Roxeth — largely a Metro-land suburb of 1920s and 1930s semis where rear extensions, loft conversions and side infills are the everyday projects. The uniform inter-war house type means Harrow's design expectations for extensions are well understood across most of the district.

Two genuine conservation areas sit inside HA2: Roxeth Hill (designated 1969), a historic village pocket at the foot of Harrow Hill, and Rayners Lane (designated 2002), which protects the Charles Holden station and the Art Deco parades on Alexandra Avenue. We confirm which side of those boundaries a property falls on before advising.

Proposed floor plan

North Harrow and Rayners Lane HA2

North Harrow and Rayners Lane (HA2) — planning at a glance

Council: London Borough of Harrow
Postcode district: HA2
Planning portal: View the Harrow planning portal
Housing stock: Mostly 1920s-30s Metro-land semis and terraces around North Harrow and Rayners Lane, with an older, tighter grain of historic buildings surviving on Roxeth Hill at the foot of the hill.
Article 4: London Borough of Harrow does not publish its Article 4 directions to the national planning register, so permitted development rights in North Harrow and Rayners Lane (HA2) can’t be confirmed from open data alone — we check the direction schedule with the council before recommending a route, as part of the fixed fee. Harrow does not publish its Article 4 boundaries to the national planning.data.gov.uk dataset, so no machine-readable row confirms coverage in HA2; conservation-area control over the Roxeth Hill and Rayners Lane areas is the main additional constraint here, per the council's own conservation-area maps.
Conservation: Roxeth HillRayners Lane
Sample streets: Roxeth Hill · West Hill · Alexandra Avenue · Rayners Lane · Imperial Drive
Local constraints: Roxeth Hill conservation area (designated 1969) protecting the historic village character and its listed and locally listed buildingsRayners Lane conservation area (designated October 2002) covering the station and the Art Deco shopping parades on Alexandra AvenueConsistent inter-war semi-detached house type with well-established rear and side-extension expectations across the district

Planning in North Harrow and Rayners Lane (HA2): what to know before you apply

Most inter-war semis in HA2 retain permitted-development rights for rear and loft work, so many projects avoid a full application. The exceptions are the Roxeth Hill and Rayners Lane conservation areas, where roofline, front-elevation and material changes face tighter control and a householder application is usually needed.

Typical North Harrow and Rayners Lane housing stock

Mostly 1920s-30s Metro-land semis and terraces around North Harrow and Rayners Lane, with an older, tighter grain of historic buildings surviving on Roxeth Hill at the foot of the hill.

Streets we regularly draw for in North Harrow and Rayners Lane

Roxeth Hill · West Hill · Alexandra Avenue · Rayners Lane · Imperial Drive

What HA2 is actually built of

Measured from 295 classified residential buildings in HA2, not from a description of the area.

North Harrow and Rayners Lane HA2 housing mix

Residential building form across the HA2 postcode district, from 295 classified buildings.

Attached on more than one side	44%
Attached on one side	49%
Detached	6%
Median building footprint	66 m²
Addresses per buildingAbove about 2 means flats and maisonettes dominate	1.15
Buildings classified	295

Source: Ordnance Survey National Geographic Database (derived statistics). Contains OS data © Crown copyright and database right 2026. Contains Royal Mail data © Royal Mail copyright and database right 2026. Extracted 2026-08-17.

House Extension Drawings for North Harrow and Rayners Lane (HA2) homes: the package and the process

Extension drawings are read for their dimensions. The proposed plan needs depth measured from the original rear wall — not from a previous extension — eaves and ridge heights taken from existing ground level, and the distance to each boundary marked. A site plan showing how much garden remains is what an officer reaches for when the amenity question comes up.

We draw the existing building accurately first, because everything else is measured from it. Where the original footprint has already been added to, that history goes on the drawing: it decides which allowances are still available and it is the first thing an officer checks against the council's own records.

The plot decides the extension type long before taste does. A mid-terrace has depth to work with and an alley if it is lucky; a semi has one clear flank; a detached house can go wide. Reading the building form first is what stops a design being drawn that the plot cannot take.

Which extension types do you draw?

Every London extension is shaped by the plot, the neighbours and the borough's design guidance. We draw them all.

Rear extension

A single-storey rear extension is often permitted development within depth limits — ideal for an open-plan kitchen-diner.

Side-return

Fills the alley beside a Victorian terrace, widening the ground floor without losing garden.

Wraparound

Combines a rear and side-return extension for a transformative ground floor, usually needing planning permission.

Double-storey

Adds space above and below, subject to tighter scale and neighbour-impact scrutiny.

Basement

Creates space downward where footprint is limited, with structural and party-wall care.

Do I need planning permission for a house extension in London?

Single-storey rear extensions within permitted development limits (up to 6m for terraced/semi-detached homes under the larger-home scheme, subject to neighbour consultation) may not need a full application. Wraparounds, double-storeys and anything in a conservation area usually do. We assess your plot and recommend the right route before drawing. The current depth, height and eaves limits are set out in full in the guide to planning permission for a rear extension, and where you would rather one practice ran the design, the application and the building-regulations stage together, Architectural Drawings covers that full scope.

How do you maximise the footprint the council will approve?

We know each borough's depth, height and daylight standards, so we design to the edge of what will be approved rather than guessing — and we check the 45-degree neighbour daylight rule and any rear building line before submission. Where a plot is tight we test a permitted-development scheme against a slightly larger householder application and show you the trade-off in space, cost and timescale, so the drawn scheme is the one that actually maximises value rather than just floor area.

Typical London extension drawing packages
Extension	Typical route	Package	Fee from
Single-storey rear	Permitted development / householder	Planning + building regs	£1,100
Side-return	Householder planning	Planning + building regs + structural	£1,600
Wraparound	Householder planning	Full package + structural	£2,200
Double-storey	Householder planning	Full package + structural	£2,400

Sheet from a house extension drawings package drawn for a North Harrow and Rayners Lane property in HA2, showing the existing and proposed arrangement at scale — A sheet from the house extension drawings package we submit to London Borough of Harrow for North Harrow and Rayners Lane (HA2) properties.

Also in North Harrow and Rayners Lane HA2

Planning Permission Planning Drawings Architectural Drawings Building Regulations Drawings Loft Conversion Drawings House Extension Drawings across Harrow House Extension Drawings across London

FAQ

House Extension Drawings in North Harrow and Rayners Lane HA2 — FAQs

How far can I extend without planning permission in London?+

Under permitted development, single-storey rear extensions can reach 3m (terraced/semi) or 4m (detached), or up to 6–8m under the prior-approval larger-home scheme — but conservation areas and Article 4 directions can remove these rights. We check your property first.

Do extension drawings include structural calculations?+

Our full package includes structural drawings and calculations coordinated in-house, so your builder can price and build without waiting on an engineer.

How long do extension drawings take?+

Typically about 7 days from survey to a full drawing set delivered to your online portal.

Will my rear extension need a party wall agreement?+

If you build up to or on a shared boundary, excavate near a neighbour's foundations, or cut into a party wall for a steel, the Party Wall etc. Act 1996 usually applies. Our drawings show the works clearly so a party wall surveyor — or your neighbour — can see exactly what is proposed, which keeps that process quick.

Can I extend a house in a conservation area?+

Yes, but conservation areas and Article 4 directions commonly remove permitted development for rear and side extensions, so the work needs a full householder application designed to the council's heritage guidance. We confirm your property's designation before recommending a route.

Do I need planning permission for a loft conversion in Harrow?+

Harrow's Metro-land semis and detached houses in Rayners Lane, Kenton and Stanmore suit hip-to-gable and dormer lofts, which frequently qualify as permitted development within the volume limits. The exceptions are the conservation areas — Harrow on the Hill and Pinner's historic core — and the Article 4 wards. We check your address and can confirm permitted development with a Lawful Development Certificate.

What does Harrow expect for a rear extension on a 1930s semi?+

The council pays close attention to preserving the rhythm and building line of its interwar suburban streets, so extensions are expected to respect the established line and roof form. Many single-storey rear extensions still fall within permitted development; where a full application is needed, we design to the borough's residential guidance so it validates and approves without repeated revisions.

Can I extend a home in Harrow on the Hill or Pinner?+

Yes, but these historic conservation areas carry a heritage setting and long views the council protects closely, so permitted development is often restricted and a full, context-led application is required. We design to the character of the area — materials, proportions and rooflines — and evidence the heritage considerations so the submission stands up.

How long does Harrow Council take to decide?+

Harrow determines most householder applications within the statutory eight-week period once validated. The commonest delay is a validation query, so we prepare Harrow submissions to the council's checklist with correctly scaled existing and proposed drawings and a location plan to keep the application on track.

How much do planning drawings cost in Harrow?+

We work to a fixed fee agreed upfront, usually around 30% below an architect's charge for the same council-accepted drawings, with free redraws until Harrow approves. The figure depends on the scheme — a dormer loft differs from a double-storey extension — so we confirm it once we understand your project rather than billing by the hour.

Free Fixed Quote

Get your free North Harrow and Rayners Lane planning assessment

Tell us your North Harrow and Rayners Lane (HA2) address and ambition — we'll confirm feasibility, local constraints and a fixed fee within one working day.