House Extensions · HA1 Harrow
Fixed-fee house extension drawings for Harrow, Harrow on the Hill, West Harrow, Greenhill in the HA1 postcode, drawn by an MCIAT-chartered architectural technologist and submitted to Harrow Council. Harrow protects the Harrow on the Hill conservation area, dominated by Harrow School and the historic hilltop village, alongside standard suburban householder control across the rest of HA1.
MCIAT chartered drawings for planning, building regs, lofts and extensions — fixed fees 30% below typical London architects. Tell us what you need and we’ll reply the same working day.
House extensions in Harrow are dominated by single-storey rear and side-return additions on HA1's victorian and edwardian houses around harrow on, with double-storey and wrap-around schemes where the plot allows. Harrow Council weighs depth, height and neighbour daylight; many extensions across Harrow, Harrow on the Hill, West Harrow, Greenhill are Permitted Development, which we confirm with a Lawful Development Certificate before you build.
The whole spectrum — rear extensions, side returns, wraparounds, double-storey, basement digs. Planning-led design with detailed technical phase, ideal for victorian and edwardian houses around harrow on typical of Harrow.
Across Harrow, Harrow on the Hill, West Harrow, Greenhill in HA1, the dominant property is victorian and edwardian houses around harrow on the hill, with inter-war semis toward west harrow and town-centre flats. That stock shapes what house extension drawings looks like here: the right approach for a period terrace differs from a mansion-block flat or a new-build, and Harrow Council judges each on design quality and neighbour impact. We survey the specific Harrow property, confirm the planning route — Permitted Development, a Lawful Development Certificate, or full planning — and draw a council-ready set tailored to the HA1 streetscape.
Housing stock in HA1: Victorian and Edwardian houses around Harrow on the Hill, with inter-war semis toward West Harrow and town-centre flats.
Within the district: Harrow, Harrow on the Hill, West Harrow, Greenhill.
Streets we know in HA1: the streets around Harrow on the Hill and Harrow School, the West Harrow estate roads and the terraces near Harrow-on-the-Hill station. Each road has its own building line, boundary treatment and precedent that Harrow Council weighs when assessing a house extension drawings scheme.
Conservation areas: Harrow on the Hill, West Harrow / Roxborough fringe. Inside these, most external work needs full planning and a Heritage Statement.
Getting around HA1: Harrow-on-the-Hill (Metropolitan line and Chiltern Railways) and Harrow & Wealdstone serve HA1.
Regeneration: Harrow falls within or beside the Harrow town centre, which shapes local planning policy and design expectations.
Property values: around £325,000 for a flat and £550,000-£950,000 for a house — a useful gauge of the build value an extension or loft adds in HA1.
Borough character: Outer north-west London suburban; Harrow on the Hill has exceptionally strict heritage controls; rest of borough permissive.
Measured existing survey, photographic record, Article 4 and conservation check specific to Harrow before we quote.
2–3 design options at concept stage — alternative layouts, glazing, roof forms.
Site location plan, existing and proposed plans, elevations, sections, D&AS where required.
Part L thermal, Part B fire, Part M accessibility, structural strategy.
Steel beam, foundation, lintel design. Chartered engineer sign-off.
Party Wall notices where needed; Thames Water Build Over Agreement where within 3m of a public sewer.
Single planning or building-regs submission.
Planning + building regs + structural.
Listed, conservation or complex sites.
Yes, but the historic hilltop village sits in the Harrow on the Hill conservation area, dominated by Harrow School, where rear and side extensions and roof changes need full planning with a Heritage Statement. We design to match the period and submit to Harrow. Toward West Harrow and Greenhill, Permitted Development often applies.
Very — the conservation area protects the School buildings, the historic streets and the prominent hilltop skyline, so extensions are assessed for their effect on that setting and on long views. We produce a careful Heritage Statement and design within those constraints for a realistic chance of consent.
Usually yes on the inter-war semis around West Harrow and Greenhill — a hip-to-gable plus rear dormer within the volume allowance, confirmed by a Lawful Development Certificate. Inside the Harrow on the Hill conservation area, roof changes need full planning. We confirm which applies to your HA1 road.
From inter-war semis around £550,000 to Harrow on the Hill houses near £950,000, a well-designed extension or loft adds family space and value. The hilltop conservation area raises the bar, so professional drawings matter — and our fixed fee keeps the cost predictable.
Our fixed fee for house extension drawings in Harrow starts at £1,225 — no hourly billing. With Harrow property at around £325,000 for a flat and £550,000-£950,000 for a house, the professional drawing fee is a small fraction of the value the work adds to HA1's victorian and edwardian houses around harrow on. Harrow Council charges its own statutory application fee on top (currently £258 for a householder planning application, £578 for a full application). We quote the drawings as one fixed price and the free site survey covers every HA1 address.
For a HA1 project across Harrow, Harrow on the Hill, West Harrow, Greenhill, expect roughly 3–4 weeks from instruction to submission: week 1 the measured survey, weeks 2–3 the drawings and your revisions, then validation and the statutory determination by Harrow Council (8 weeks for a householder application). We carry the Harrow application through every officer query to the decision.
Harrow (HA1) sits primarily in Harrow, so applications are decided by Harrow Council. Article 4 in force in the borough: No. Conservation areas within HA1 include Harrow on the Hill, West Harrow / Roxborough fringe, where full planning and a Heritage Statement are required. We confirm the planning route for your exact address before quoting.
Almost always. Any structural work behind house extension drawings in Harrow — new openings, steel beams, loft floors, foundations — needs Building Regulations approval covering structure (Part A), fire escape (Part B) and insulation (Part L), submitted to Harrow Council Building Control or an approved inspector. On HA1's typically terraced and semi-detached stock, a Party Wall notice to adjoining neighbours is normally required before the steelwork. We coordinate both as part of the Complete package.
In value terms, yes. With Harrow (HA1) property at around £325,000 for a flat and £550,000-£950,000 for a house, a well-designed extension or loft typically returns more than it costs in added floor area and sale value, while our fixed drawing fee from £1,225 keeps the professional cost predictable. The bigger risk is an unapproved or non-compliant scheme — which is why council-ready drawings and a clean Building Control sign-off matter on HA1 homes.
From £840.
From £840.
From £1,225.
From £1,575.
From £995.
From £1,950.
From £350.
From £540.
From £450.
From £1,225.
Pick a slot that suits you. No obligation and no sales pressure — just straight answers on your planning route, fixed fee and timescale.
Every HA1 postcode district we draw in, the stock that dominates it and the authority that validates a house extension there. HA1 fees below are the statutory England rates for 2026, not house extension estimates.
| Postcode | Area | Dominant stock | What it means for a house extension |
|---|---|---|---|
| HA1 | Harrow / Harrow on the Hill | Georgian and Victorian houses, listed buildings | A house extension at an HA1 address in Harrow / Harrow on the Hill is determined by Harrow Council under its own Local Plan policies for Harrow / Harrow on the Hill. |
| HA1 | Harrow on the Hill | Georgian and Victorian houses, listed buildings | Harrow on the Hill sits inside HA1; house extension proposals here are determined by Harrow Council. |
| HA2 | North Harrow / South Harrow | 1930s semi-detached | Adjoining district to HA1, also inside Harrow for house extension purposes. |
| HA3 | Harrow Weald / Kenton / Wealdstone | 1930s semi-detached | Adjoining district to HA1, also inside Harrow for house extension purposes. |
| HA7 | Stanmore | 1930s semi-detached, Edwardian villas | Adjoining district to HA1, also inside Harrow for house extension purposes. |
Roof pitch, wall build-up and plot depth change every few HA1 streets, and each one changes what a house extension can achieve at that address.
Conservation areas covering HA1 (Harrow / Harrow on the Hill): Harrow Council runs 29, and Harrow Weald, Harrow on the Hill, Pinner Village are the ones HA1 (Harrow / Harrow on the Hill) owners meet most. A house extension inside a HA1 (Harrow / Harrow on the Hill) conservation area loses permitted development, so the HA1 (Harrow / Harrow on the Hill) submission is a householder application at £258 decided in 8 weeks — not a £120 prior approval decided in 6 weeks. In Stanmore a house extension is judged on the street elevation first.
Article 4 and your HA1 (Harrow / Harrow on the Hill) house extension: Harrow Council has made no borough-wide direction, so permitted development for a house extension in HA1 (Harrow / Harrow on the Hill) generally survives outside HA1 (Harrow / Harrow on the Hill) conservation areas and listed curtilages. A Lawful Development Certificate at £129 is how a HA1 owner records that a house extension was lawful.
What HA1 (Harrow / Harrow on the Hill) is built from: 1930s semi-detached dominates; Edwardian villas in Harrow on the Hill and Pinner; Metropolitan Green Belt in Stanmore and Harrow Weald; post-war flats around Harrow Central. Outer north-west London suburban; Harrow on the Hill has exceptionally strict heritage controls; rest of borough permissive. That mix decides the house extension route in HA1 (Harrow / Harrow on the Hill) more than the postcode does. Our fixed fee for house extensions in HA1 (Harrow / Harrow on the Hill) starts at £1,225, against £1,750 for the Complete package that carries a HA1 (Harrow / Harrow on the Hill) scheme through Harrow Council planning and building regulations together.
Sources for this HA1 house extension page: borough policies maps and conservation-area registers (2025–26), Royal Mail postcode district boundaries, the Town and Country Planning (Fees for Applications) (England) Regulations, the Town and Country Planning (General Permitted Development) (England) Order 2015 as amended, and the Party Wall etc. Act 1996.
Free fixed quote in 60 seconds. From £1,225. MCIAT chartered.
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