Back-of-house extension drawings for Hillingdon homes — the glazed kitchen-diner across the rear, drawn to Hillingdon Council's depth and daylight limits, delivered in days and revised free until your decision, with a free approval-odds check first.
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.
The rear extension is the workhorse of Hillingdon home improvement — it is how a dark back kitchen becomes an open family room facing the garden. Because the borough is built largely from interwar Metro-land semi-detached houses, Edwardian terraces around Uxbridge and West Drayton and detached houses and cottages in the rural western villages, most back walls sit close to a neighbour on at least one side, and that proximity, not the design, is what Hillingdon Council scrutinises. The council reads the proposal against Hillingdon Local Plan and the HDAS: Residential Extensions SPD, and the first line an officer draws is the 45-degree splay from the neighbour's nearest window.
So the drawings live or die on geometry. We set the depth against the exact permitted-development figure, hold the eaves and the flat-roof or lantern build-up under the 4-metre height ceiling, and show the projection tested against both the 45-degree plan angle and the 25-degree section angle to the neighbouring windows. A large slice of the borough sits in Green Belt to the west, where extensions face the openness test rather than ordinary householder policy, so the rear elevation is composed around it rather than corrected after an objection.
Where the property sits in a conservation area — Old Uxbridge, Harefield Village, Ickenham Village, Ruislip Village and Eastcote among Hillingdon's — the larger-home extension route is switched off and even a modest rear addition needs consent. 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. We confirm the designation before the survey.
Many single-storey rear extensions in Hillingdon are permitted development and need no application. You will normally need to apply to Hillingdon Council, or use the larger-home prior-approval route, if any of these apply:
We draw the depth, the roof build-up and the daylight splays to each neighbour on the page — the tests Hillingdon Council's officers apply first — and submit a validation-complete pack, whether that is a lawful development certificate, a larger-home prior-approval notice or a full householder application.
Below is Hillingdon Council's real householder decision record, taken 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. Rear extensions turn most often on neighbour daylight and depth, so a drawing pack that proves those tests upfront is decided faster and refused less often than a DIY submission.
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 Uxbridge, Ruislip and Ickenham, the approved rear extension is typically a single-storey glazed box within the depth limit, roofed either flat with a lantern or in a shallow mono-pitch, and finished in brick or render to match the host wall. On the borough's interwar metro-land semi-detached houses, keeping the projection to the permitted-development figure often avoids an application entirely; where owners want the full 6 metres, the larger-home route succeeds when the neighbour-consultation period passes without a sustained objection.
The design guidance polices the spacing and building line of Metro-land semis so paired houses keep their rhythm. We keep the extension inside the daylight splays, set any glazed roof below the first-floor cill, and retain the garden depth Hillingdon Council expects — so the back elevation answers the amenity case before a neighbour can lodge one. Two-storey rear extensions we draw with the 7-metre boundary gap and privacy screening resolved on the plan.
We draw rear extensions on every street in the borough. A few of the neighbourhoods where Hillingdon back-of-house projects come up most often:
Rear extension drawings for Uxbridge's the town centre with its Old Uxbridge conservation area and Edwardian terraces — depth-checked, daylight-tested and drawn to Hillingdon Council's guidance.
Rear extension drawings for Ruislip's Metro-land semis around the Ruislip Village conservation area — depth-checked, daylight-tested and drawn to Hillingdon Council's guidance.
Rear extension drawings for Ickenham's a village green surrounded by interwar suburban housing — depth-checked, daylight-tested and drawn to Hillingdon Council's guidance.
Rear extension drawings for Harefield's a rural Green Belt village of cottages and detached homes — depth-checked, daylight-tested and drawn to Hillingdon Council's guidance.
Rear extension drawings for Northwood's affluent detached and semi-detached houses on leafy plots — depth-checked, daylight-tested and drawn to Hillingdon Council's guidance.
Rear extension drawings for Hayes's mixed interwar and postwar estates near the former industrial belt — depth-checked, daylight-tested and drawn to Hillingdon Council's guidance.
How far you can extend at the back in Hillingdon depends on your house type and the route you take. This is how the options compare.
| Route | Depth allowed | Consent needed | What Hillingdon Council checks |
|---|---|---|---|
| Standard permitted development | 3m terrace/semi · 4m detached | Lawful development certificate (optional) | Depth, 4m height, materials |
| Larger-home prior approval | 6m terrace/semi · 8m detached | Prior-approval notice + neighbour consultation | Neighbour objections on amenity |
| Full householder application | Beyond the above, or two-storey | Full planning permission | Daylight (45°/25°), bulk, garden retained |
| Conservation area | Case by case | Full planning permission | Character, roof form, boundary treatment |
The larger-home route is switched off on designated land — conservation areas such as Old Uxbridge and Harefield Village and Article 4 streets need a full application.
A fixed process built around how Hillingdon Council validates and decides rear-extension applications — most drawings are submission-ready within seven days of survey.
Send us your Hillingdon postcode and house type. We confirm your conservation and Article 4 status, how much rear-extension depth you have under permitted development, and score your odds against live Hillingdon Council decisions.
We measure the original rear wall, floor and eaves levels, side and rear boundary distances and the neighbours' window positions — the numbers the depth limit and daylight splays depend on.
Chartered designers develop the single or two-storey rear extension to your brief, drawn inside the permitted-development limits or to Hillingdon Council's extension design guidance, with the daylight angles shown.
We submit the certificate, prior-approval notice or application, handle validation and case-officer queries, and revise the drawings free until Hillingdon Council issues its decision.
Often not. A single-storey rear extension up to 3 metres deep on a terrace or semi, or 4 metres on a detached house, and no higher than 4 metres, is usually permitted development in Hillingdon. You will need to involve Hillingdon Council for anything deeper via the larger-home route, for two-storey rear extensions, and for any rear extension in a conservation area such as Old Uxbridge and Harefield Village, where those permitted-development rights fall away.
The larger-home extension scheme lets a single-storey rear extension reach 6 metres on a terrace or semi, or 8 metres on a detached house — double the standard allowance. It is not automatic: you submit a prior-approval notification to Hillingdon Council, neighbours are consulted, and if one objects on amenity grounds the council rules on it. It also does not apply on designated land such as Hillingdon's conservation areas.
It is the daylight test Hillingdon Council applies to protect neighbours. Drawn on plan, a line at 45 degrees from the midpoint of the neighbour's nearest ground-floor window should not be crossed by your extension; a companion 25-degree line is checked in section. If the projection breaches it, the extension is likely to be shortened or refused, so we test and prove it on the drawings before submission.
A two-storey rear extension almost always needs a full householder application to Hillingdon Council, as it sits outside permitted development on most homes. The council checks that it stays at least 7 metres from the rear boundary, does not overbear the neighbours and avoids new overlooking. We resolve the boundary gap, privacy and daylight on the plans so the application is decided on its merits.
Frequently, yes. If the rear extension involves work to a shared wall, building up to the boundary, or excavating foundations near a neighbour's structure, the Party Wall etc. Act applies and you must serve notice — this is separate from Hillingdon Council's planning decision. We flag it early and can prepare the drawings a party-wall surveyor needs alongside the planning set.
We price each Hillingdon rear extension on its own footprint and send a fixed, no-obligation quote within one working day. It covers the full drawing pack with free revisions until Hillingdon Council approves, and we confirm at the outset whether your extension is permitted development, needs prior approval, or a full application. Call 020 7864 7245 to begin.
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