The fast route to a deep single-storey rear extension in West Cambridge — up to 6 metres on an attached house or 8 on a detached one — via Cambridge City Council's prior approval scheme rather than a full planning application.
Cambridge City Council granted 90% of the householder planning decisions it made in its latest published year — 3 points above the 87% England-wide householder average. The architectural interest of the Conduit Head Road modernist group closely controls alterations and extensions, which is where a policy-literate drawing pack earns its keep. Its dominant Edwardian (1901–1910) and interwar (1918–1939) housing stock sets the design brief on most streets.
Class A and Class B set the thresholds — a rear dormer to 40m³ on a terrace or 50m³ on a semi or detached, and a single-storey rear extension to 3m on a terrace or 4m on a detached house — beyond which Cambridge City Council needs a full application. West Cambridge carries at least one Article 4 direction, and conservation areas including West Cambridge, Conduit Head Road and Storey's Way remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in West Cambridge is determined against an 8-week statutory target.
Conduit Head Road (a rare cluster of 1930s modernist houses inside its own conservation area), Storey's Way (spacious Arts-and-Crafts villas laid out by St John's College), Adams Road (large academic houses close to the science site), Grange Road (generous college and academic villas) and Madingley Road (detached houses on the western approach to the city) — these are the West Cambridge pockets our drawings cover most. Heritage designations here include West Cambridge, Conduit Head Road and Storey's Way. Cambridge City Council weighs each proposal against the Cambridge Local Plan 2018 and the emerging Greater Cambridge Local Plan, where the generous villa plots and mature planting on Storey's Way and Adams Road are protected from cramped infill. Some of the larger academic villas have been divided into flats for university staff, which hold no householder permitted-development rights.. On roofs the borough is hipped and gabled tile roofs on the Arts-and-Crafts villas and flat roofs on the Conduit Head Road modernist houses, over large detached Arts-and-Crafts and academic villas, 1930s modernist houses on Conduit Head Road and Edwardian and interwar houses.
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 West Cambridge and Conduit Head Road 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.
West Cambridge is largely large detached Arts-and-Crafts and academic villas, 1930s modernist houses on Conduit Head Road and Edwardian and interwar houses. The architectural interest of the Conduit Head Road modernist group closely controls alterations and extensions, which matters here because an objecting neighbour puts amenity squarely in front of a case officer. The west side sits within the West Cambridge, Conduit Head Road and Storey's Way conservation areas — the first two noted for their inter-war modernist and Arts-and-Crafts houses — and Article 4 directions remove permitted-development rights across them.
The scheme is available where all of these hold. Fail any one and it is a full application to Cambridge City Council instead:
We prepare the notification pack Cambridge City 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 Cambridge City Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Cambridge approves around 90% of applications, but on the west side the modernist and Arts-and-Crafts conservation areas and their generous plots are the decisive constraints. 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, England, 1 April 2025 - 31 March 2026). 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 Conduit Head Road, Storey's Way and Adams Road, 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 generous villa plots and mature planting on Storey's Way and Adams Road are protected from cramped infill. 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 West Cambridge. A few of the areas where deep rear extensions come up most often:
Prior approval drawings for Conduit Head Road — a rare cluster of 1930s modernist houses inside its own conservation area — dimensioned to the 6m and 8m limits and prepared for Cambridge City Council's neighbour consultation.
Prior approval drawings for Storey's Way — spacious Arts-and-Crafts villas laid out by St John's College — dimensioned to the 6m and 8m limits and prepared for Cambridge City Council's neighbour consultation.
Prior approval drawings for Adams Road — large academic houses close to the science site — dimensioned to the 6m and 8m limits and prepared for Cambridge City Council's neighbour consultation.
Prior approval drawings for Grange Road — generous college and academic villas — dimensioned to the 6m and 8m limits and prepared for Cambridge City Council's neighbour consultation.
Prior approval drawings for Madingley Road — detached houses on the western approach to the city — dimensioned to the 6m and 8m limits and prepared for Cambridge City 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 West Cambridge 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 Cambridge City 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 Cambridge City Council before starting and the conditions on height, materials and land coverage are met. The scheme is not available on designated land. This applies to your West Cambridge address specifically.
It is a notification, not an application for permission. You tell Cambridge City 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. This applies to your West Cambridge address specifically.
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 West Cambridge address specifically. Cambridge City Council is the decision-maker.
No. The larger home extension scheme is unavailable on designated land, which includes conservation areas such as West Cambridge and Conduit Head Road, 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 Cambridge City 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 West Cambridge address specifically. Cambridge City 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 West Cambridge address specifically. Cambridge City Council is the decision-maker.
We quote each West Cambridge 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 Cambridge City Council determines it. Call 020 7864 7245 to start.
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Same fixed quotes, same fast drawings — wherever your project is.