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.
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.
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
What W4 is actually built of
Measured from 530 classified residential buildings in W4, not from a description of the area.
Chiswick W4 housing mix
Residential building form across the W4 postcode district, from 530 classified buildings.
| Attached on more than one side | 55% |
|---|---|
| Attached on one side | 37% |
| Detached | 8% |
| Median building footprint | 74 m² |
| Addresses per buildingAbove about 2 means flats and maisonettes dominate | 1.68 |
| Buildings classified | 530 |
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.
Rear Extension Drawings for Chiswick (W4) homes: the package and the process
Depth is the number the application turns on, and it has to be measured from the original rear wall of the house rather than from whatever is there now. The drawings carry that dimension, the eaves and ridge heights, the position of any rooflight, and the boundary distances on both sides.
Where the scheme goes beyond the standard allowance and relies on the larger home extension route, the drawings serve a second purpose: they are what the council sends to the neighbours during the consultation. A clear, dimensioned proposed elevation answers the objection about overshadowing before it is made.
Depth is limited by the plot as much as by the rules. A long garden behind a terrace can take the full allowance, while a short one runs out before the rules do — and on a semi or detached house the same depth reads very differently from the boundary.
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.
Designing the kitchen-diner: rooflights, bi-folds and daylight
Most rear extensions exist to create one open-plan kitchen, dining and living space, so the drawing work focuses on getting light and flow right within the depth you are allowed.
- Structural opening sized for bi-fold or sliding doors across most of the rear elevation
- Rooflights or a roof lantern positioned to light the centre of the room, away from the shadow line of the main house
- Open-plan layout tested against the 45-degree rule, which protects daylight to your neighbours' windows and can limit how close a flank wall or roof comes to the boundary
- Floor build-up and threshold detail coordinated so the new floor meets the existing one without a step
| Route | When it applies | Typical fee |
|---|---|---|
| Permitted development (Lawful Development Certificate) | Depth within 3m (terraced/semi) or 4m (detached), height and materials within PD limits | PD/LDC pack ~£950–£1,450 |
| Larger home extension (prior approval) | Depth up to 6m (terraced/semi) or 8m (detached), with neighbour notification | from £1,100 |
| Full householder planning permission | Extension exceeds PD/larger-home limits, or the property is in a conservation area with an Article 4 direction | Full Planning pack ~£1,600–£2,400 |
| Planning + Building Regulations (structural) | Combined planning and construction-ready pack with structural calculations for the opening and roof | Planning + Building Regs pack ~£2,200–£3,850 |
Rear Extension Drawings in Chiswick W4 — FAQs
How much does a rear extension cost to design in London?+
Do I need an architect for a rear extension?+
How long does it take to get rear extension drawings?+
What is the 45-degree rule?+
Will I need a Party Wall Agreement for a rear extension?+
Do I need planning permission for an extension in Hounslow?+
What extra control applies in Bedford Park?+
Does Heathrow or the river affect my Hounslow project?+
How long does Hounslow Council take to decide?+
How much do planning drawings cost in Hounslow?+
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