The fast route to a deep single-storey rear extension in Hounslow — up to 6 metres on an attached house or 8 on a detached one — via Hounslow Council's prior approval scheme rather than a full planning application.
Hounslow Council granted 86% of the householder planning decisions it made in its latest published year — 1 point below the 87% England-wide householder average. Side-return and mansard schemes dominate in Chiswick, where officers weigh roof bulk against a strongly uniform terrace roofscape, which is where a policy-literate drawing pack earns its keep. Its dominant Georgian (1714–1837), Victorian (1837–1901), Edwardian (1901–1910), interwar (1918–1939) and postwar (1945–1970) housing stock sets the design brief on most streets.
The permitted-development ceilings are fixed: 40m³ of new roof volume for a terraced loft and 50m³ for a semi or detached house under Class B, plus a 3m single-storey rear extension on a terrace or 4m on a detached house under Class A. Hounslow carries at least one Article 4 direction, and conservation areas including Bedford Park, Old Chiswick and Strand-on-the-Green remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in Hounslow is determined against an 8-week statutory target.
Chiswick (Victorian and Edwardian terraces wrapped around the Bedford Park garden suburb), Brentford (older riverside terraces alongside recent waterfront redevelopment), Isleworth (the Old Isleworth riverside conservation area and Georgian frontages), Osterley (interwar semis on the fringe of Osterley Park), Feltham (postwar and interwar suburban estates to the south-west) and Hounslow (the town centre with mixed terraces and converted flats) — these are the Hounslow pockets our drawings cover most. Heritage designations here include Bedford Park, Old Chiswick, Strand-on-the-Green, Wellesley Road and Old Isleworth. Hounslow Council weighs each proposal against Hounslow Local Plan and the Residential Extension Guidelines SPD, where the borough's western edge sits under Heathrow flight paths, so glazing, ventilation and noise mitigation surface on larger schemes. Converted terraces are common through central Chiswick and Brentford, and flats and maisonettes carry no householder permitted-development rights.. On roofs the borough is London butterfly and valley roofs on the Chiswick terraces and hipped roofs on the interwar semis, over Victorian and Edwardian terraces across Chiswick, interwar semi-detached houses around Osterley and Hounslow and converted period flats and maisonettes.
The ordinary Class A limits stop a single-storey rear extension at 3 metres on an attached house and 4 on a detached one. The larger home extension scheme doubles both, on condition that the council is told first. That notification is not an application for permission — the council cannot refuse on design, materials or policy grounds. It can only consider the effect on the amenity of adjoining premises, and only if a neighbour actually objects during the 21-day consultation.
The other conditions still apply and are strict: single storey only, no higher than 4 metres, eaves no higher than the existing eaves, and no more than half the land around the original house covered. It is not available on designated land, so a house in a conservation area such as Bedford Park and Old Chiswick cannot use it at all. Materials must be similar to the existing house, and the extension must not include a veranda, balcony or raised platform.
Hounslow is largely Victorian and Edwardian terraces across Chiswick, interwar semi-detached houses around Osterley and Hounslow and converted period flats and maisonettes. Side-return and mansard schemes dominate in Chiswick, where officers weigh roof bulk against a strongly uniform terrace roofscape, which matters here because an objecting neighbour puts amenity squarely in front of a case officer. Bedford Park — the pioneering garden suburb shared with Ealing — carries a long-standing Article 4 direction, and the Chiswick and Old Isleworth conservation areas remove permitted-development rights on many of their period streets.
The scheme is available where all of these hold. Fail any one and it is a full application to Hounslow Council instead:
We prepare the notification pack Hounslow Council needs — plans, elevations, a site plan with the adjoining owners identified — and manage the 21-day neighbour consultation so the 42-day clock is not restarted by an incomplete submission.
Below is Hounslow Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Hounslow grants a fair share of householder applications, with terrace roofscape in the Chiswick conservation areas the dominant constraint on loft and rear schemes. Prior approval turns on neighbour amenity alone, so the drawings that matter are the ones showing the relationship to the boundary.
Source: MHCLG planning application statistics (householder decisions, rolling year). Compare every borough on our London approval-rate league table.
Tell us about your project and get a fixed, no-obligation quote back within one working day. If you don't need planning permission at all, we'll tell you that too — for free.
Across Chiswick, Brentford and Isleworth, the notifications that clear without objection are the ones that treat the neighbour as the audience. We show the extension in section against the boundary, demonstrate the 45-degree daylight relationship to the nearest habitable window, and where the plot is tight we taper the depth away from the boundary rather than running the full 6 metres to the fence.
The borough's western edge sits under Heathrow flight paths, so glazing, ventilation and noise mitigation surface on larger schemes. Where an objection does arrive, the council's assessment is narrow: loss of light, outlook and overbearing effect on the adjoining property, nothing else. A pack that has already answered those three points on the drawings usually survives an objection, whereas one that leaves them to the officer's imagination usually does not.
We prepare prior-approval notifications across Hounslow. A few of the areas where deep rear extensions come up most often:
Prior approval drawings for Chiswick — Victorian and Edwardian terraces wrapped around the Bedford Park garden suburb — dimensioned to the 6m and 8m limits and prepared for Hounslow Council's neighbour consultation.
Prior approval drawings for Brentford — older riverside terraces alongside recent waterfront redevelopment — dimensioned to the 6m and 8m limits and prepared for Hounslow Council's neighbour consultation.
Prior approval drawings for Isleworth — the Old Isleworth riverside conservation area and Georgian frontages — dimensioned to the 6m and 8m limits and prepared for Hounslow Council's neighbour consultation.
Prior approval drawings for Osterley — interwar semis on the fringe of Osterley Park — dimensioned to the 6m and 8m limits and prepared for Hounslow Council's neighbour consultation.
Prior approval drawings for Feltham — postwar and interwar suburban estates to the south-west — dimensioned to the 6m and 8m limits and prepared for Hounslow Council's neighbour consultation.
Prior approval drawings for Hounslow — the town centre with mixed terraces and converted flats — dimensioned to the 6m and 8m limits and prepared for Hounslow Council's neighbour consultation.
Same extension, two routes, very different tests.
| Route | Depth allowed | What the council may consider | Timescale |
|---|---|---|---|
| Ordinary Class A permitted development | 3m attached / 4m detached | Nothing — no application needed | Immediate |
| Larger home extension prior approval | 6m attached / 8m detached | Amenity of adjoining premises, only if a neighbour objects | 21-day consultation, 42-day determination |
| Full householder application | No fixed limit | Design, materials, policy, amenity, everything | 8-week target |
| Any of these on designated land | 3m / 4m only | Prior approval scheme unavailable | Full application beyond the limits |
Limits and procedure from the GPDO 2015, Schedule 2, Part 1, Class A and paragraph A.4, made permanent by amendment in 2019.
A process built around the 21-day consultation, which is where these schemes are won or lost.
Send us your Hounslow postcode and house type. We confirm whether the property is on designated land, whether the scheme is available, and what depth you can realistically take.
We measure the original rear wall, eaves height, boundary distances and the neighbouring windows that the amenity assessment will turn on.
We draw the extension to the 6m or 8m limit with the boundary relationship shown in section, and prepare the written description and adjoining-owner details Hounslow Council needs to start the consultation.
We submit, track the 21-day consultation and the 42-day determination, respond to any objection on amenity grounds, and revise free until the decision.
Three metres on a terraced or semi-detached house and four on a detached one under ordinary permitted development. Under the larger home extension prior approval scheme those double to six and eight metres, provided you notify Hounslow Council before starting and the conditions on height, materials and land coverage are met. The scheme is not available on designated land.
It is a notification, not an application for permission. You tell Hounslow Council what you intend to build, it writes to the adjoining owners, and they have 21 days to object. If nobody objects, you may build. If someone does, the council assesses the effect on the amenity of adjoining premises and must decide within 42 days. Design and policy are not in scope.
The council then considers the impact on the amenity of the adjoining property — loss of light, loss of outlook, and overbearing effect — and nothing else. It cannot refuse because it dislikes the design or the materials. We prepare the drawings so those three questions are already answered in section and on the site plan, which is what usually carries an objected scheme through. This applies to your Hounslow address specifically. Hounslow Council is the decision-maker.
No. The larger home extension scheme is unavailable on designated land, which includes conservation areas such as Bedford Park and Old Chiswick, national landscapes, national parks and world heritage sites. On those properties the ordinary 3-metre and 4-metre limits apply, and anything deeper needs a full householder application to Hounslow Council.
Twenty-one days for the neighbour consultation, and a maximum of 42 days from a valid submission for the council to determine it. If the council does not respond within 42 days you may proceed as notified. That deadline is the scheme's real advantage over a full application, and it is why validation completeness matters so much. This applies to your Hounslow address specifically. Hounslow Council is the decision-maker.
Yes — always. Prior approval deals only with the planning position. A 6-metre rear extension still needs building control approval for foundations, structure, drainage, thermal performance and fire safety, and the beam over the opening into the existing house needs designing and calculating. We prepare both sets so the notified scheme is the buildable one. This applies to your Hounslow address specifically. Hounslow Council is the decision-maker.
We quote each Hounslow scheme individually, because plot shape and the boundary relationship drive the work, and send a fixed, no-obligation quote within one working day. It covers the notification pack and free revisions until Hounslow Council determines it. Call 020 7864 7245 to start.
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Same fixed quotes, same fast drawings — wherever your project is.