Two-storey extension drawings for Hillingdon homes — bedroom above, living space below, drawn against the 3-metre projection and 7-metre boundary rules and to Hillingdon Council's design guidance, delivered in days and revised free until your decision.
Hillingdon Council granted 84% of the householder planning decisions it made in its latest published year — 3 points below the 87% England-wide householder average. A large slice of the borough sits in Green Belt to the west, where extensions face the openness test rather than ordinary householder policy, which is where a policy-literate drawing pack earns its keep. Its dominant Edwardian (1901–1910), interwar (1918–1939) and postwar (1945–1970) 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 Hillingdon Council needs a full application. Hillingdon carries at least one Article 4 direction, and conservation areas including Old Uxbridge, Harefield Village and Ickenham Village remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in Hillingdon is determined against an 8-week statutory target.
Uxbridge (the town centre with its Old Uxbridge conservation area and Edwardian terraces), Ruislip (Metro-land semis around the Ruislip Village conservation area), Ickenham (a village green surrounded by interwar suburban housing), Harefield (a rural Green Belt village of cottages and detached homes), Northwood (affluent detached and semi-detached houses on leafy plots) and Hayes (mixed interwar and postwar estates near the former industrial belt) — these are the Hillingdon pockets our drawings cover most. Heritage designations here include Old Uxbridge, Harefield Village, Ickenham Village, Ruislip Village and Eastcote. Hillingdon Council weighs each proposal against Hillingdon Local Plan and the HDAS: Residential Extensions SPD, where the design guidance polices the spacing and building line of Metro-land semis so paired houses keep their rhythm. On roofs the borough is hipped roofs on the 1930s semis and gabled roofs on the older village cottages, over interwar Metro-land semi-detached houses, Edwardian terraces around Uxbridge and West Drayton and detached houses and cottages in the rural western villages.
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. Hillingdon is largely interwar Metro-land semi-detached houses, Edwardian terraces around Uxbridge and West Drayton and detached houses and cottages in the rural western villages, and hipped roofs on the 1930s semis and gabled roofs on the older village cottages 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.
A large slice of the borough sits in Green Belt to the west, where extensions face the openness test rather than ordinary householder policy. Ruislip Village and the Harefield and Ickenham conservation areas carry tight controls, and Article 4 directions on some of these older village streets strip out the permitted-development rights suburban owners otherwise assume.
Some two-storey rear extensions are permitted development. You will need a full application to Hillingdon 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 Hillingdon Council checks first — then submit a validation-complete pack.
Below is Hillingdon Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Hillingdon grants a fair share of householder applications, with Green Belt openness in the western villages and roof and spacing changes to interwar semis the recurring pinch points. 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, rolling year). Compare every borough on our London approval-rate league table.
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Across Uxbridge, Ruislip and Ickenham, 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 interwar metro-land semi-detached houses, 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 design guidance polices the spacing and building line of Metro-land semis so paired houses keep their rhythm. 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 Hillingdon. A few of the areas where they come up most often:
Two storey extension drawings for Uxbridge — the town centre with its Old Uxbridge conservation area and Edwardian terraces — dimensioned against the 3m and 7m limits and drawn to Hillingdon Council's guidance.
Two storey extension drawings for Ruislip — Metro-land semis around the Ruislip Village conservation area — dimensioned against the 3m and 7m limits and drawn to Hillingdon Council's guidance.
Two storey extension drawings for Ickenham — a village green surrounded by interwar suburban housing — dimensioned against the 3m and 7m limits and drawn to Hillingdon Council's guidance.
Two storey extension drawings for Harefield — a rural Green Belt village of cottages and detached homes — dimensioned against the 3m and 7m limits and drawn to Hillingdon Council's guidance.
Two storey extension drawings for Northwood — affluent detached and semi-detached houses on leafy plots — dimensioned against the 3m and 7m limits and drawn to Hillingdon Council's guidance.
Two storey extension drawings for Hayes — mixed interwar and postwar estates near the former industrial belt — dimensioned against the 3m and 7m limits and drawn to Hillingdon 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 Hillingdon 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 Hillingdon Council validates and decides two-storey applications.
Send us your Hillingdon postcode and garden depth. We measure the 7-metre boundary rule against your plot, confirm designation status, and score your odds against live Hillingdon 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 Hillingdon 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 Hillingdon, the 7-metre rule is what most commonly forces a full application to Hillingdon 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 Hillingdon gardens this is decisive, and we measure it on survey before any design work rather than discovering it at validation. Hillingdon Council is the decision-maker.
Not under permitted development — two-storey side extensions always need a full application to Hillingdon 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.
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 Hillingdon address specifically. Hillingdon 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 Hillingdon Council's planning decision, so we flag the notice period early and detail the junction on the drawings.
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 Hillingdon address specifically. Hillingdon Council is the decision-maker.
We quote each Hillingdon 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 Hillingdon Council approves. Call 020 7864 7245 to start.
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