Two-storey extension drawings for West Cambridge homes — bedroom above, living space below, drawn against the 3-metre projection and 7-metre boundary rules and to Cambridge City Council's design guidance, delivered in days and revised free until your decision.
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.
Adding at first floor changes the question the case officer asks. A single-storey extension is judged mostly on daylight and garden loss; a two-storey extension is judged on overlooking, bulk against the neighbouring roofline, and whether it reads as part of the house or bolted onto it. West Cambridge is largely large detached Arts-and-Crafts and academic villas, 1930s modernist houses on Conduit Head Road and Edwardian and interwar houses, and hipped and gabled tile roofs on the Arts-and-Crafts villas and flat roofs on the Conduit Head Road modernist houses set what a matching roof actually means here.
The permitted-development route exists but is narrow: 3 metres of rear projection, a 7-metre stand-off from the rear boundary, eaves and ridge no higher than the original, and side-facing upper windows obscure-glazed and non-opening below 1.7 metres above floor level. Most two-storey schemes fail one of those, usually the 7-metre boundary rule on a shorter garden, and go in as a full application instead. We establish which route applies before designing, because it changes the drawing set.
The architectural interest of the Conduit Head Road modernist group closely controls alterations and extensions. 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.
Some two-storey rear extensions are permitted development. You will need a full application to Cambridge City Council if any of these apply:
We set the projection and boundary distance on the site plan, prove the roof-pitch match on the elevations, and specify obscure glazing on the side windows — the three things Cambridge City Council checks first — then submit a validation-complete pack.
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. Two-storey schemes attract more neighbour comment than any other householder work, so the overlooking and daylight case has to be made on the drawings.
Source: MHCLG planning application statistics (householder decisions, England, 1 April 2025 - 31 March 2026). Compare every borough on our London approval-rate league table.
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Across Conduit Head Road, Storey's Way and Adams Road, the schemes that succeed set the first floor back from the ground floor, keep the ridge below the original, and treat the flank wall as blank or obscure-glazed. On large detached arts-and-crafts and academic villas, matching the eaves line matters more than matching the brick: an extension that carries the existing eaves through reads as original even in a different material.
The generous villa plots and mature planting on Storey's Way and Adams Road are protected from cramped infill. We draw the 45-degree daylight test from the neighbour's nearest habitable window, show the window positions in section, and set out the steel and foundation implications early — a two-storey extension changes the load path, so the structural design and the planning design have to be developed together rather than in sequence.
We draw two-storey extensions across West Cambridge. A few of the areas where they come up most often:
Two storey extension drawings for Conduit Head Road — a rare cluster of 1930s modernist houses inside its own conservation area — dimensioned against the 3m and 7m limits and drawn to Cambridge City Council's guidance.
Two storey extension drawings for Storey's Way — spacious Arts-and-Crafts villas laid out by St John's College — dimensioned against the 3m and 7m limits and drawn to Cambridge City Council's guidance.
Two storey extension drawings for Adams Road — large academic houses close to the science site — dimensioned against the 3m and 7m limits and drawn to Cambridge City Council's guidance.
Two storey extension drawings for Grange Road — generous college and academic villas — dimensioned against the 3m and 7m limits and drawn to Cambridge City Council's guidance.
Two storey extension drawings for Madingley Road — detached houses on the western approach to the city — dimensioned against the 3m and 7m limits and drawn to Cambridge City Council's guidance.
The first-floor limits are tighter than the ground-floor ones. This is how the common cases compare.
| Scheme | Permitted development? | Deciding limit | What Cambridge City Council checks |
|---|---|---|---|
| Two-storey rear, 3m projection, 7m+ to boundary | Often yes | 3m projection / 7m boundary | Roof match, side-window glazing |
| Two-storey rear, under 7m to boundary | No — full application | Rear-boundary distance | Overlooking, daylight, garden loss |
| Two-storey side extension | No — full application | Side elevation | Gap to boundary, street rhythm |
| Two-storey wraparound | No — full application | Combined footprint | Bulk, massing, neighbour amenity |
| Any two-storey on designated land | No — full application | Designation | Character and appearance |
Limits from the GPDO 2015, Schedule 2, Part 1, Class A — two-storey rear extension conditions.
A fixed process built around how Cambridge City Council validates and decides two-storey applications.
Send us your West Cambridge postcode and garden depth. We measure the 7-metre boundary rule against your plot, confirm designation status, and score your odds against live Cambridge City Council decisions.
We measure the original rear wall, eaves and ridge heights, garden depth and every neighbouring window that faces the site — the inputs the daylight and overlooking case is built from.
Chartered designers develop the two-storey addition to your brief with the roof and eaves resolved, and we coordinate the load path so the structural scheme and the planning scheme are the same building.
We submit the application, manage validation and case-officer queries, and revise the drawings free until Cambridge City Council issues its decision.
Often, but not always. A two-storey rear extension can be permitted development if it projects no more than 3 metres, sits at least 7 metres from the rear boundary, does not exceed the existing eaves and ridge, and has obscure-glazed non-opening side windows below 1.7 metres. In West Cambridge, the 7-metre rule is what most commonly forces a full application to Cambridge City Council.
No part of a permitted-development two-storey rear extension may come within 7 metres of the boundary opposite the rear wall of the house. It exists to protect the neighbour behind you from being overlooked at first floor. On shorter West Cambridge gardens this is decisive, and we measure it on survey before any design work rather than discovering it at validation. Cambridge City Council is the decision-maker.
Not under permitted development — two-storey side extensions always need a full application to Cambridge City Council. They are assessed on the gap to the boundary, whether the street's rhythm of spaces between houses survives, and whether the extension is subordinate to the original. Setting the first floor back from the front building line and down from the ridge is what usually makes the difference. This applies to your West Cambridge address specifically.
Overlooking is the most common objection, and it is answerable on the drawings. We position habitable-room windows away from neighbouring gardens, obscure-glaze and fix shut anything on the flank below 1.7 metres, and show the sight lines in section. Where the geometry is tight, a rooflight or a high-level window gives the same daylight without the mutual overlooking that draws objections. This applies to your West Cambridge address specifically. Cambridge City Council is the decision-maker.
Almost certainly. Excavating within 3 metres of a neighbouring structure and building on or up to the boundary both trigger the Party Wall etc. Act 1996, and a two-storey extension usually does both. It is entirely separate from Cambridge City Council's planning decision, so we flag the notice period early and detail the junction on the drawings. This applies to your West Cambridge address specifically.
Yes. Adding a floor changes the load path from roof to foundation, so beams, padstones and foundation depths all need designing and calculating for building control. Planning and building regulations are separate consents, and the structural set is what building control assesses — we prepare both so the approved 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 two-storey extension individually, because plot depth, roof form and structural complexity vary house to house, and send a fixed, no-obligation quote within one working day. It covers the drawing pack with free revisions until Cambridge City Council approves. Call 020 7864 7245 to start.
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