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Free 2026 London Planning Report — Isleworth TW7

Computer-generated image of a red-brick house with a hipped tiled roof, two small dormers, a pale green front door, a white garage door and a block-paved drive, with part of a white weatherboarded wing on the right
TW7 · Isleworth · Hounslow

Planning and building regulation drawings in Isleworth (TW7)

TW7 gives a homeowner two quite different jobs to think about. Isleworth starts at the Thames, where the old core around the church and Church Street keeps Georgian and early-Victorian terraces and cottages, and Lower Square, Mill Plat and North Street are among Isleworth's streets. In Spring Grove and the wider streets the housing changes to substantial Victorian and Edwardian semi-detached and detached villas. The riverside end brings its own questions: the setting beside the water, listed buildings near All Saints Church and the waterfront, and low-lying ground close to the tideway that can raise flood-zone points before a design is even sketched.

  • MCIAT chartered technologists
  • London Borough of Hounslow granted 75% of 704 householder applications
  • Drawings in about 7 days

Free Isleworth planning assessment

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Osterley is a separate story. It is an interwar suburb of substantial semis and detached houses on generous plots around Osterley Park, on roads such as Ellington Road, Jersey Road, Alderney Avenue and Addison Avenue. Houses of that size suit a full-width rear extension, a two-storey side addition or a carefully designed loft, and the plots are big enough that an ambitious scheme can run past what permitted development allows and need a full householder application. The park setting, the Osterley Park and Spring Grove conservation areas and the street trees all feed into how scale, materials and foundations are judged.

Spring Grove appears in both neighbourhoods, which is a reminder that a postcode district is a poor guide to what applies on a given road. Two houses a few doors apart can sit on either side of a conservation boundary. Before we draw anything we look up the designations, listing and any tree protection against your exact address, so the drawings answer the questions the council will actually ask.

Planning in Isleworth: what to know before you apply

Hounslow validates householder applications against its local checklist and then decides them on the character of the street and the setting. The borough controls design closely in its conservation areas, and TW7 includes Isleworth Riverside, Spring Grove and Osterley Park. In a conservation area, roof enlargements, side extensions and rear extensions of more than one storey are not permitted development, so those need a planning application. Old Isleworth carries no householder Article 4 direction, and none is published for Osterley, though the council does apply Article 4 controls to HMO conversions in parts of the borough, which matter if you plan to let to three to six unrelated sharers. Flats have no householder permitted development rights at all. Aircraft noise toward Heathrow and Thames flood-zone considerations can also shape a proposal.

Applications are decided by London Borough of Hounslow — its planning pages.

Check your route

Does your Isleworth project need planning permission?

Route check · Isleworth (TW7)

Listed building?
Conservation area?
Likely permitted development — no planning applicationNeeds checking
  • A single-storey rear extension up to 4 m deep on a detached house, or 3 m on any other house, is Class A permitted development subject to the height and materials conditions.
  • An Article 4 direction applies here and may withdraw this freedom — the schedule must be checked before relying on it.
  • One or more constraints are unknown — we check the council's registers as part of the free appraisal.
  • Where permitted development applies, a lawful development certificate proves it for lenders and buyers.

Sources: GPDO 2015, Schedule 2, Part 1 · Planning Portal — common projects · Building Regulations 2010 — when approval is needed

This is a first-pass indication from the national rules, not planning advice for your property. Your council's registers, any Article 4 schedule and the exact dimensions decide it — the free appraisal checks all three before we recommend a route.

Confirm it with a free appraisal

Isleworth (TW7) in numbers

What London Borough of Hounslow has decided, and what TW7 is built of — the two facts that shape every job here.

Householder planning decisions — London Borough of Hounslow

Isleworth (TW7) applications are decided by London Borough of Hounslow; these are its published householder figures for the last four quarters.

Householder applications decided2025 Q2 to 2026 Q1704
Granted526
Refused178
Grantedof 704 decisions · England 90%75%
Decided within 8 weeksof 404, excluding prior approvals97%

Source: Ministry of Housing, Communities and Local Government (PS2 district planning application statistics). Open Government Licence v3.0 Extracted 2026-09-22.

Permitted development prior approvals — London Borough of Hounslow

How the larger-home-extension route has fared with London Borough of Hounslow, which decides TW7 notifications.

Larger home extension prior approvals — not required2024 Q2 to 2026 Q1263
Prior approval granted54
Prior approval refused138
Grantedof 192 determined28%

Source: Ministry of Housing, Communities and Local Government (PS1 district planning application statistics). Open Government Licence v3.0 Extracted 2026-09-22.

Planning appeals — London Borough of Hounslow

Refusals in TW7 can be appealed to the Planning Inspectorate; this is London Borough of Hounslow's householder appeal record.

Householder appeals determined2021–2026352
Allowed175
Allowedof 352 · England 36%50%

Source: Planning Inspectorate appeals casework. Open Government Licence v3.0 Extracted 2026-09-22.

Conservation areas and Article 4 directions — London Borough of Hounslow

Register counts for London Borough of Hounslow. A count describes what the council has published, never a rank against another council.

Conservation areas in the register28 dated, 1968–201443
Article 4 directions in the register3
Areas covered by an Article 4 direction3

Source: MHCLG Planning Data Platform. Open Government Licence v3.0 Extracted 2026-09-22.

What TW7 is built of

Residential building form across Isleworth (TW7), from 412 classified buildings — the fact that decides party walls, side returns and loft headroom before any policy does.

Attached on more than one side41%
Attached on one side52%
Detached7%
Median building footprint66 m²
Addresses per buildingAbove about 2 means flats and maisonettes dominate2.02
Buildings classified412

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 2026-09-22.

  1. Day 0Measured survey of your Isleworth property — or your existing plans if you have them.
  2. About 7 daysDrawings issued for your approval. Free redraws until you are happy.
  3. SubmissionWe validate against London Borough of Hounslow’s checklist and submit on your behalf.
  4. Council: 8-week targetHouseholder applications carry an 8-week statutory target. London Borough of Hounslow decided 97% of 404 recent householder applications inside it.

Source: Ministry of Housing, Communities and Local Government (PS2 district planning application statistics). Open Government Licence v3.0 Extracted 2026-09-22.

Neighbourhoods

Streets and neighbourhoods in TW7

IsleworthGeorgian riverside core with Victorian and Edwardian villa streetsOsterleypredominantly interwar
Nearby

Nearby postcode districts

Cranford TW5Brentford TW8Hounslow TW3Richmond TW9Twickenham TW2Ham & Petersham TW10Twickenham TW1Teddington TW11
FAQ

Isleworth (TW7) — FAQs

Is my Isleworth house inside a conservation area?+
It depends on the street. Isleworth Riverside covers the old waterside core and Spring Grove covers the villa streets inland, and Osterley Park is a third, but not every TW7 address sits inside one. We check the boundary for your address first, because it decides whether a roof extension or side extension can go ahead without a planning application.
Will the trees on my Osterley road affect an extension?+
They can. Mature street trees on the interwar avenues are often protected, and root zones can restrict where foundations go. We check for protection and allow for it in the design, so the footprint and structure are drawn with the trees in mind from the start.
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