Rear dormer drawings for Westminster roofs — the box across the back slope that turns a low attic into a full-height room, drawn to Westminster City Council's guidance and the volume limits, delivered in days and revised free until your decision, with a free approval-odds check first.
Westminster City Council granted 87% of the householder planning decisions it made in its latest published year — level with the 87% England-wide householder average. Basement excavation is tightly policed on depth, garden coverage and construction impact given the density of listed and stucco stock, which is where a policy-literate drawing pack earns its keep. Its dominant Georgian (1714–1837) and Victorian (1837–1901) housing stock sets the design brief on most streets.
The permitted-development ceilings are fixed: 40m³ of new roof volume for a terraced loft and 50m³ for a semi or detached house under Class B, plus a 3m single-storey rear extension on a terrace or 4m on a detached house under Class A. Westminster carries at least one Article 4 direction, and conservation areas including Bayswater, Maida Vale and Pimlico remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in Westminster is determined against an 8-week statutory target.
Bayswater (stucco terraces around leafy garden squares), Maida Vale (red-brick and stucco mansion blocks along wide avenues), Pimlico (Thomas Cubitt's uniform white stucco terraces), Marylebone (Georgian and Victorian terraces mixed with mansion flats), Belgravia (grand stucco terraces served by their own mews) and Queen's Park (the model-cottage streets of the Queen's Park Estate on the Westminster side) — these are the Westminster pockets our drawings cover most. Heritage designations here include Bayswater, Maida Vale, Pimlico, Marylebone and Queen's Park. Westminster City Council weighs each proposal against the Westminster City Plan and the Basements SPD, where mansard and roof extensions are steered by the roof-extension policy to sit within an unbroken terrace profile. Larger stucco houses in Bayswater and Marylebone are widely converted into flats, which carry no householder permitted-development rights.. On roofs the borough is mansard roofs to the stucco terraces and concealed butterfly roofs behind parapets, over stucco-fronted Georgian and Victorian terraces, purpose-built mansion flats and mews houses to the rear of the grand streets.
The box dormer is the workhorse loft, and most of Westminster is built for it — the borough runs to stucco-fronted Georgian and Victorian terraces, purpose-built mansion flats and mews houses to the rear of the grand streets under mansard roofs to the stucco terraces and concealed butterfly roofs behind parapets, and a flat-roofed box across the rear slope is the cheapest cubic metre of full-height space those roofs give up. Westminster City Council tests the dormer against the Westminster City Plan and the Basements 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. Basement excavation is tightly policed on depth, garden coverage and construction impact given the density of listed and stucco stock, so the cheeks, the window line and the material are drawn to answer it rather than invite a query.
Where Westminster's streets are protected — Bayswater, Maida Vale, Pimlico, Marylebone and Queen's Park among them — the Class B dormer right is switched off and even a modest rear box needs consent. The overwhelming majority of Westminster lies within a conservation area, and Article 4 directions across districts like Bayswater and Pimlico remove permitted-development rights on facades, roofs and windows. We confirm the designation before the box is sized.
Many rear dormers in Westminster are permitted development, but the volume and position decide it. You will normally need a full application to Westminster City 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 Westminster City Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Westminster grants a high share of householder applications, though near-total conservation-area coverage and a restrictive basement regime are the constraints behind most refusals. 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 Bayswater, Maida Vale and Pimlico, 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 mansard roofs to the stucco terraces, this returns a full-height double and en-suite from what was standing-room-only, usually inside the permitted-development volume.
Mansard and roof extensions are steered by the roof-extension policy to sit within an unbroken terrace profile. 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 Westminster City 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 Westminster dormers come up most often:
Dormer loft drawings for Bayswater's stucco terraces around leafy garden squares — volume-checked, set-back-detailed and drawn to Westminster City Council's guidance.
Dormer loft drawings for Maida Vale's red-brick and stucco mansion blocks along wide avenues — volume-checked, set-back-detailed and drawn to Westminster City Council's guidance.
Dormer loft drawings for Pimlico's Thomas Cubitt's uniform white stucco terraces — volume-checked, set-back-detailed and drawn to Westminster City Council's guidance.
Dormer loft drawings for Marylebone's Georgian and Victorian terraces mixed with mansion flats — volume-checked, set-back-detailed and drawn to Westminster City Council's guidance.
Dormer loft drawings for Belgravia's grand stucco terraces served by their own mews — volume-checked, set-back-detailed and drawn to Westminster City Council's guidance.
Dormer loft drawings for Queen's Park's the model-cottage streets of the Queen's Park Estate on the Westminster side — volume-checked, set-back-detailed and drawn to Westminster City Council's guidance.
Whether a dormer in Westminster 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 Westminster City 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 Bayswater and Maida Vale, Class B dormer rights are removed and every dormer needs a full application.
A fixed process built around how Westminster City Council validates and decides dormer applications — most drawings are submission-ready within seven days of survey.
Send us your Westminster 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 Westminster City 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 Westminster City Council's roof-alteration guidance.
We submit the certificate or application, manage validation and case-officer queries, and revise the drawings free until Westminster City 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 Westminster you will need a full application to Westminster City Council for a front or side dormer, a box that exceeds the volume, and any dormer in a conservation area such as Bayswater and Maida Vale, 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 Westminster 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. Westminster City 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 Westminster City 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 Westminster 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 Westminster City 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 Westminster City 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 Westminster 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 Westminster City 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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