Rear dormer drawings for Hillingdon roofs — the box across the back slope that turns a low attic into a full-height room, drawn to Hillingdon Council's guidance and the volume 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 box dormer is the workhorse loft, and most of Hillingdon is built for it — the borough runs to interwar Metro-land semi-detached houses, Edwardian terraces around Uxbridge and West Drayton and detached houses and cottages in the rural western villages under hipped roofs on the 1930s semis and gabled roofs on the older village cottages, and a flat-roofed box across the rear slope is the cheapest cubic metre of full-height space those roofs give up. Hillingdon Council tests the dormer against Hillingdon Local Plan and the HDAS: Residential Extensions SPD, and because permitted development turns on a number, the volume you propose against the volume you have left is the first thing an officer or a certificate checks.
That is why the arithmetic goes on the drawings. We calculate the box against the 40- or 50-cubic-metre allowance, count any earlier roof enlargement into the total, hold the flat roof below the ridge and set the face back off the eaves so the dormer reads as subordinate. 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 cheeks, the window line and the material are drawn to answer it rather than invite a query.
Where Hillingdon's streets are protected — Old Uxbridge, Harefield Village, Ickenham Village, Ruislip Village and Eastcote among them — the Class B dormer right is switched off and even a modest rear box 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 box is sized.
Many rear dormers in Hillingdon are permitted development, but the volume and position decide it. You will normally need a full application to Hillingdon Council if any of these apply:
We draw the box within its volume allowance, the flat roof below the ridge and the face set back off the eaves — the three things a dormer stands or falls on — and submit a validation-complete pack, whether that is a lawful development certificate or a full householder application.
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. A dormer is decided on volume and set-back, so a pack that shows the calculation and the eaves detail is cleared 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 dormer that goes through is the subordinate rear box: flat roof kept low, cheeks clad to recede, side windows obscure-glazed against overlooking, and the whole thing set back so the original eaves line still reads from the garden. On hipped roofs on the 1930s semis, this returns a full-height double and en-suite from what was standing-room-only, usually inside the permitted-development volume.
The design guidance polices the spacing and building line of Metro-land semis so paired houses keep their rhythm. We keep the box off the ridge, match the cheek material to the roof, and where the volume is already spent — or the street is designated — draw the dormer as a householder application composed to Hillingdon Council's roof-alteration guidance rather than push a certificate that would be refused.
We draw rear dormers on the terraced and semi-detached streets across the borough. A few of the neighbourhoods where Hillingdon dormers come up most often:
Dormer loft drawings for Uxbridge's the town centre with its Old Uxbridge conservation area and Edwardian terraces — volume-checked, set-back-detailed and drawn to Hillingdon Council's guidance.
Dormer loft drawings for Ruislip's Metro-land semis around the Ruislip Village conservation area — volume-checked, set-back-detailed and drawn to Hillingdon Council's guidance.
Dormer loft drawings for Ickenham's a village green surrounded by interwar suburban housing — volume-checked, set-back-detailed and drawn to Hillingdon Council's guidance.
Dormer loft drawings for Harefield's a rural Green Belt village of cottages and detached homes — volume-checked, set-back-detailed and drawn to Hillingdon Council's guidance.
Dormer loft drawings for Northwood's affluent detached and semi-detached houses on leafy plots — volume-checked, set-back-detailed and drawn to Hillingdon Council's guidance.
Dormer loft drawings for Hayes's mixed interwar and postwar estates near the former industrial belt — volume-checked, set-back-detailed and drawn to Hillingdon Council's guidance.
Whether a dormer in Hillingdon needs permission comes down to where it sits and how big the box is. This is how the cases compare.
| Dormer type | Permitted development? | What it gains | What Hillingdon Council checks |
|---|---|---|---|
| Rear box, within volume | Usually yes | Full-height room across the back | Volume total, 20cm eaves set-back |
| Rear box, over volume limit | No — full application | A larger room | How far over the allowance, bulk |
| Front or side dormer | No — full application | Light to the front rooms | Visibility from the street, character |
| Dormer in a conservation area | No — full application | Same space, extra scrutiny | Roof form and street appearance |
In conservation areas such as Old Uxbridge and Harefield Village, Class B dormer rights are removed and every dormer needs a full application.
A fixed process built around how Hillingdon Council validates and decides dormer applications — most drawings are submission-ready within seven days of survey.
Send us your Hillingdon postcode and roof type. We confirm your conservation and Article 4 status, work out how much permitted-development volume you have left, and score your odds against live Hillingdon Council decisions.
We measure ridge and eaves heights, roof pitch and the existing loft floor — the numbers the volume calculation, the set-back and the head heights depend on.
Chartered designers develop the box to your brief, drawn inside the Class B volume limits or, where those are exhausted or removed, to Hillingdon Council's roof-alteration guidance.
We submit the certificate or application, manage validation and case-officer queries, and revise the drawings free until Hillingdon Council issues its decision.
Often not. A rear box dormer within 40 cubic metres on a terrace, or 50 on a semi or detached house, set back at least 20 centimetres from the eaves and kept below the ridge, is usually permitted development. In Hillingdon you will need a full application to Hillingdon Council for a front or side dormer, a box that exceeds the volume, and any dormer in a conservation area such as Old Uxbridge and Harefield Village, where those rights are removed.
The permitted-development limit is a volume, not a footprint: 40 cubic metres of added roof space on a terraced house and 50 on a semi-detached or detached one, and any earlier loft enlargement counts against that total. In Hillingdon the box must also sit below the ridge and back from the eaves. We measure your roof and calculate the exact volume you have left before drawing. Hillingdon Council is the decision-maker.
Not under permitted development. A dormer on the front roof slope, or one facing a highway, always needs a full application to Hillingdon Council, because it changes how the house reads from the street. Rear box dormers are far more likely to be approved — or to be permitted development outright — which is why almost every Hillingdon dormer we draw sits on the back slope.
Often, on a terrace or semi. If the dormer or the loft steelwork meets the party wall with your neighbour, the Party Wall etc. Act applies and notice must be served before work starts — separately from Hillingdon Council's planning decision. We flag the party-wall junction on the drawings so a surveyor can be appointed early and the build is not held up.
If your dormer is permitted development, a lawful development certificate from Hillingdon Council is council-stamped proof of it — worth holding, because a buyer's solicitor will ask for it when you sell. We prepare and submit the certificate with the same measured drawing pack that shows the box within its volume allowance.
We price each Hillingdon dormer individually, because the roof pitch and the volume left vary house to house, 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 box is permitted development or needs an application. Call 020 7864 7245 to start.
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