Mansard drawings for Westminster terraces — the rebuilt roof with a steep, near-vertical rear slope that adds a full storey of loft, drawn to Westminster City Council's roofline and streetscape rules, 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 mansard is the maximum-volume loft, and Westminster's stock is where it belongs — the borough runs to stucco-fronted Georgian and Victorian terraces, purpose-built mansion flats and mews houses to the rear of the grand streets, and on a period terrace a mansard rebuilds the roof at roughly seventy degrees to create almost a full new floor rather than the part-height room a dormer returns. Westminster City Council assesses it against the Westminster City Plan and the Basements SPD, and because the whole roof changes shape the test is the street: whether the new profile continues the terrace or breaks it.
That is what the drawings have to settle. We set the mansard behind the original parapet or eaves, hold it to the ridge height of neighbouring mansards where the terrace already has them, and detail the slate face, the dormer windows within it and the party walls to both sides so the addition reads as part of the row. Basement excavation is tightly policed on depth, garden coverage and construction impact given the density of listed and stucco stock, and on a roof this prominent that is the argument that has to be won on the page.
Much of Westminster's terraced stock is designated — Bayswater, Maida Vale, Pimlico, Marylebone and Queen's Park among the areas — and there a mansard is judged on whether it restores or respects the historic roofline. 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. Some terraces already have a consistent mansard line an addition can follow; others do not, and we establish which before drawing.
A mansard in Westminster always needs a full application to Westminster City Council — rebuilding the roof puts it well outside permitted development. These are the points the council weighs:
We draw the new roof behind the parapet, the slope and ridge matched to the terrace, the slate face and dormer windows, and the party walls to both neighbours — the roofline and streetscape relationships Westminster City Council's officers check first — and submit a validation-complete 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 mansard is decided on roofline and streetscape, so a scheme drawn to continue the terrace is cleared faster and refused less often than one that fights it.
Source: MHCLG planning application statistics (householder decisions, rolling year). Compare every borough on our London approval-rate league table.
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Across Bayswater, Maida Vale and Pimlico, the mansard that goes through is the one that disappears into the row: set behind the parapet, its ridge matched to neighbouring mansards, the front slope in natural slate with traditional dormer windows, and the whole storey reading as though the terrace was always that height. On the borough's stucco-fronted georgian and victorian terraces, this is the single biggest volume the roof can give — close to a full floor.
Mansard and roof extensions are steered by the roof-extension policy to sit within an unbroken terrace profile. We follow any established mansard line on the terrace, keep the slope and materials traditional, and where a row has none yet, draw a design that could set the pattern rather than break it — the argument Westminster City Council needs to grant on a roof this visible.
We draw mansard roofs on the period-terrace streets across the borough. A few of the neighbourhoods where Westminster mansards come up most often:
Mansard loft drawings for Bayswater's stucco terraces around leafy garden squares — roofline-matched, slate-detailed and drawn to Westminster City Council's guidance.
Mansard loft drawings for Maida Vale's red-brick and stucco mansion blocks along wide avenues — roofline-matched, slate-detailed and drawn to Westminster City Council's guidance.
Mansard loft drawings for Pimlico's Thomas Cubitt's uniform white stucco terraces — roofline-matched, slate-detailed and drawn to Westminster City Council's guidance.
Mansard loft drawings for Marylebone's Georgian and Victorian terraces mixed with mansion flats — roofline-matched, slate-detailed and drawn to Westminster City Council's guidance.
Mansard loft drawings for Belgravia's grand stucco terraces served by their own mews — roofline-matched, slate-detailed and drawn to Westminster City Council's guidance.
Mansard loft drawings for Queen's Park's the model-cottage streets of the Queen's Park Estate on the Westminster side — roofline-matched, slate-detailed and drawn to Westminster City Council's guidance.
A mansard wins the most space of any loft but asks the most of the planning case. This is how it compares in Westminster.
| Loft type | Planning route | Space gained | What Westminster City Council checks |
|---|---|---|---|
| Mansard | Always a full application | Close to a full extra storey | Roofline, streetscape, terrace match |
| Rear dormer | Often permitted development | A room across the back slope | Volume and eaves set-back |
| Hip-to-gable | Full application | Full width where the roof is hipped | Balance with the paired neighbour |
| Rooflights only | Usually permitted development | Light and headroom, no new shape | Rooflights within the existing slope |
In conservation areas such as Bayswater and Maida Vale, a mansard is judged on how it sits within the protected roofline of the terrace.
A fixed process built around how Westminster City Council validates and decides mansard applications — most drawings are submission-ready within seven days of survey.
Send us your Westminster postcode and terrace type. We confirm your conservation and Article 4 status, check whether the row already has a mansard line to follow, and score your odds against live Westminster City Council decisions.
We measure the parapet, ridge and party walls, and the roofline of the neighbouring houses — the numbers the new slope, its height and the terrace match depend on.
Chartered designers develop the rebuilt roof to your brief, drawn to Westminster City Council's roof-alteration and conservation guidance with the slope, slate face, dormers and party walls detailed on the page.
We submit the householder application, manage validation and case-officer queries, and revise the drawings free until Westminster City Council issues its decision.
Always. A mansard rebuilds the roof into a steep rear slope with a flat top, and that wholesale change of roof shape is well outside permitted development — so it needs a full householder application to Westminster City Council on every street, designated or not. On a terrace in a conservation area such as Bayswater and Maida Vale the roofline is protected, so the design is scrutinised more closely still.
It is a rebuilt roof with a steep, near-vertical rear slope and a small flat top, which creates almost a full extra storey inside — far more than a dormer returns. Westminster's period terraces are the classic mansard candidates, and where a row already carries mansards a new one that matches the line is the most likely of all lofts to be approved despite being the largest. Westminster City Council is the decision-maker.
Because it reshapes the whole roof rather than adding a box to it. The steep slope pushes the walls out almost to vertical and the flat top lifts the ceiling, so the usable floor runs nearly the full footprint of the house at head height — close to a complete storey. That is why, in Westminster, a mansard is chosen when a dormer or hip-to-gable will not give enough room. Westminster City Council is the decision-maker.
It can, but the case is harder. Where a terrace already has a consistent mansard line, matching it is straightforward; on an unbroken row, Westminster City Council weighs whether your mansard would break the skyline or could set an acceptable pattern for the street. We draw the design to sit within the terrace and make that argument on the elevations rather than leave it to chance.
Almost certainly, on both sides. A mansard rebuilds the roof up to and across the party walls with the neighbours either side, so the Party Wall etc. Act applies to each and notice must be served before work starts — separately from Westminster City Council's planning decision. We detail both party walls on the drawings and flag the notices early so surveyors can be appointed without holding up the build.
We price each Westminster mansard individually, because the terrace, the roofline match and the party-wall detailing vary street to street, 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 the roofline case at the outset. Call 020 7864 7245 to start.
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