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Free 2026 London Planning Report — Rear Extension Drawings in Chiswick W4

Side return extension drawings for a Victorian terrace in Chiswick W4, London Borough of Hounslow
Chiswick · W4 · Hounslow

Rear Extension Drawings in Chiswick W4

Fixed-fee, MCIAT-chartered rear extension drawings for Chiswick (W4) homeowners — London Borough of Hounslow validation and local constraints handled from the start.

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Chiswick (W4) sits in Hounslow, and its housing is mostly late-Victorian and Edwardian terraces and semis on the grid between Chiswick High Road and the Thames. These are houses with real rear-garden depth, which is why side-return and wraparound extensions are the recurring project here rather than the basement digs common further into central London.

The designation picture is unusual for a suburban-feeling district. Hounslow operates a borough-wide Article 4 direction removing the right to convert a house to a small HMO, so an HMO scheme anywhere in W4 needs a full application — the direction is not tied to any conservation area. A second direction removes permitted development rights for changes of use creating new dwellings under Class MA/ZA. On top of that, the Chiswick House and Turnham Green conservation areas protect the historic parkland setting and the Victorian frontages respectively. We establish which of those apply to an address before drawing to Hounslow's guidance.

Side return extension drawings for a Victorian terrace in Chiswick W4, London Borough of Hounslow
Isometric illustration of a Chiswick W4 home rear extension drawings design
Proposed floor plan
Chiswick W4

Planning in Chiswick (W4): what to know before you apply

W4 falls under Hounslow's borough-wide Article 4 direction removing the right to convert a dwellinghouse (C3) to a small HMO (C4), so HMO conversions need a full planning application regardless of where in the district they sit. A further direction removes permitted development rights for changes of use that would result in new dwellings (Class MA/ZA). Two conservation areas apply — Chiswick House, protecting the historic parkland setting, and Turnham Green, protecting the Victorian street frontages. The district's deep rear gardens make side-return and wraparound extensions the common project type.

Typical Chiswick housing stock

Late-Victorian and Edwardian terraces and semi-detached houses on the grid of streets between Chiswick High Road and the river, with generous rear gardens and original bay frontages, set around the historic parkland of Chiswick House.

Streets we regularly draw for in Chiswick

Chiswick High Road · Devonshire Road · Grove Park Road · Duke Road

Rear Extension Drawings for Chiswick (W4) homes: the package and the process

Every rear extension drawings we prepare for an Chiswick property is drawn to London Borough of Hounslow’s validation standards and tuned to the W4 constraints above. Here is what the drawing package covers and how the process runs from first survey to approval.

A single-storey rear extension is the most common way London homeowners add space, usually taking the form of an open-plan kitchen-diner that opens onto the garden through bi-fold or sliding doors, with rooflights or a roof lantern bringing daylight deep into the plan. Because depth and height are tightly controlled by permitted development rules and by the 45-degree rule that protects neighbouring windows, the design work sits as much in checking what the council will allow as in drawing what you want.

DrawingsDirect draws rear extensions for permitted development, the larger home extension prior-approval scheme and full householder planning, with structural calculations for the opening and roof produced in-house by our MCIAT-chartered team. If your project also involves widening the kitchen sideways or adding a second storey, see our Side Return, Wraparound and Double Storey Extension pages — many London rear extensions grow into one of those during design.

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

Many single-storey rear extensions qualify as permitted development, meaning no planning application is needed, provided depth, height and materials stay within set limits. That changes if your property sits in a conservation area or is subject to an Article 4 direction, both of which can remove permitted development rights across a street or borough — in that case a full householder planning application is required regardless of size.

Even where an extension qualifies, most homeowners obtain a Lawful Development Certificate to confirm that status in writing before building — useful for mortgage lenders, buyers and Building Control. We check your property against your borough's constraints before recommending a route.

How deep can a single-storey rear extension go?

Depth is the main constraint on a rear extension, and it depends on your house type and whether you use standard permitted development or the larger home extension scheme.

Permitted development

Standard permitted development allows a single-storey rear extension up to 3 metres deep for terraced and semi-detached houses, or 4 metres for detached houses, generally with eaves height limited to match or stay close to the existing house.

Larger home extension scheme

The prior-approval scheme extends this to 6 metres for terraced and semi-detached houses and 8 metres for detached houses. Your council writes to affected neighbours; if none object within the notification period, approval follows without a full planning application. If an objection is raised, the council assesses the impact on neighbouring light and outlook itself, rather than automatically refusing, so a well-considered design still has a good chance of approval.

Rear extension routes at a glance
RouteWhen it appliesTypical fee
Permitted development (Lawful Development Certificate)Depth within 3m (terraced/semi) or 4m (detached), height and materials within PD limitsPD/LDC pack ~£950–£1,450
Larger home extension (prior approval)Depth up to 6m (terraced/semi) or 8m (detached), with neighbour notificationfrom £1,100
Full householder planning permissionExtension exceeds PD/larger-home limits, or the property is in a conservation area with an Article 4 directionFull Planning pack ~£1,600–£2,400
Planning + Building Regulations (structural)Combined planning and construction-ready pack with structural calculations for the opening and roofPlanning + Building Regs pack ~£2,200–£3,850

Also in Chiswick W4

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FAQ

Rear Extension Drawings in Chiswick W4 — FAQs

How much does a rear extension cost to design in London?+
Rear extension drawings start from £1,100, with the final fee set by the route your extension takes — permitted development, prior approval or full planning — and whether you need building regulations and structural calculations bundled in. The fee is fixed and agreed upfront.
Do I need an architect for a rear extension?+
No. DrawingsDirect is an MCIAT-chartered architectural technologist practice, producing the same council-accepted drawings as an architect for a fixed fee typically around 30% lower.
How long does it take to get rear extension drawings?+
Drawings are typically ready around 7 days from survey. Once submitted, councils have a statutory 8-week period to determine a standard householder planning application.
What is the 45-degree rule?+
It is a daylight test many London councils apply to check that a rear extension does not block too much light to a neighbour's nearest window, measured as a line drawn at 45 degrees from that window. We check it before submission, not after a refusal.
Will I need a Party Wall Agreement for a rear extension?+
Only if your foundations or new walls sit on or near the boundary with a neighbouring property. A straightforward rear extension set within your own plot often does not trigger the Party Wall etc. Act 1996, unlike a Side Return or Wraparound extension, which usually does.
Do I need planning permission for an extension in Hounslow?+
It depends on the area. The interwar semis of Osterley, Hounslow and Feltham often retain permitted development rights for rear extensions and lofts, while the Chiswick terraces and Bedford Park sit within conservation areas where those rights are removed. We check your address against the designations first and can confirm permitted development with a Lawful Development Certificate.
What extra control applies in Bedford Park?+
Bedford Park is one of West London's most tightly controlled conservation areas, with detailed control over materials, rooflines, windows and front elevations. A standard permitted-development dormer or cladding change usually won't apply; instead we design to the area's Arts-and-Crafts character and prepare a full householder application with the elevations and materials the council expects.
Does Heathrow or the river affect my Hounslow project?+
They can. Toward the west of the borough, aircraft-noise considerations near Heathrow may influence habitable-room and glazing design, and along the Thames at Strand-on-the-Green and Isleworth the flood zone must be addressed. We evidence these considerations within the application where they apply so the council can validate and approve without repeated revisions.
How long does Hounslow Council take to decide?+
Hounslow determines most householder applications within the statutory eight-week period once validated; Bedford Park, conservation and riverside cases can involve additional consultation. We prepare submissions to the council's validation checklist to avoid the drawing queries that cause most delays.
How much do planning drawings cost in Hounslow?+
We agree a fixed fee before starting, typically around 30% below an architect's fee for the same council-accepted drawings, with free redraws until Hounslow approves. A suburban Osterley extension and a Bedford Park application differ in the evidence required, so we quote once we understand your address and project rather than by the hour.
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