Annexe and granny-flat drawings for Westminster homes — designed to stay ancillary to the main house rather than become a separate dwelling, drawn to Westminster City Council's policies, delivered in days and revised free until your decision.
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.
Councils do not decide annexes on square metres. They decide whether, once built, the accommodation forms part of one planning unit with the main house or a second one beside it. Westminster City Council looks at whether the garden is shared or divided, whether the annexe has its own street access and address, whether the occupier could live there entirely independently, and whether the two households would function as one. That is the whole case, and it is made or lost on the layout.
Westminster is largely stucco-fronted Georgian and Victorian terraces, purpose-built mansion flats and mews houses to the rear of the grand streets, which shapes the realistic options: converting part of the existing house, extending it, or building a detached unit in the garden. A detached annexe can sometimes sit under Class E as an outbuilding incidental to the enjoyment of the dwellinghouse — but sleeping accommodation is generally not "incidental", so a garden annexe with a bedroom usually needs its own permission rather than relying on outbuilding rights.
In Westminster's conservation areas — including Bayswater and Maida Vale — a garden building is also judged on its effect on the character of the area, which limits height and footprint before the use question is reached. 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.
An annexe almost always needs an application to Westminster City Council. Expect one where any of these apply:
We plan the annexe so its relationship to the main house is visible on the page — shared garden, connected access, a layout that reads as one household — and set out the case Westminster City Council has to test, rather than leaving the officer to assume the worst.
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. Annexe applications are decided on use as much as design, so the supporting case matters as much as the elevations.
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 annexes that succeed keep one shared garden, take access past the main house rather than from the street, and are modest against the host building — single storey where the plot is overlooked, and set back from boundaries. On stucco-fronted georgian and victorian terraces, converting an integral garage or a rear ground floor is often approved more readily than a detached garden unit, because the ancillary relationship is self-evident.
Basement excavation is tightly policed on depth, garden coverage and construction impact given the density of listed and stucco stock. Where Westminster City Council grants permission, it commonly attaches a condition tying occupation of the annexe to the main dwelling. That condition is not a problem to be avoided — it is usually the mechanism that makes approval possible, and we draft the application on that basis rather than pretending the annexe is something it is not.
We draw annexes across Westminster. A few of the areas where multigenerational schemes come up most often:
Annexe and granny-flat drawings for Bayswater — stucco terraces around leafy garden squares — planned to stay ancillary and drawn to Westminster City Council's policies.
Annexe and granny-flat drawings for Maida Vale — red-brick and stucco mansion blocks along wide avenues — planned to stay ancillary and drawn to Westminster City Council's policies.
Annexe and granny-flat drawings for Pimlico — Thomas Cubitt's uniform white stucco terraces — planned to stay ancillary and drawn to Westminster City Council's policies.
Annexe and granny-flat drawings for Marylebone — Georgian and Victorian terraces mixed with mansion flats — planned to stay ancillary and drawn to Westminster City Council's policies.
Annexe and granny-flat drawings for Belgravia — grand stucco terraces served by their own mews — planned to stay ancillary and drawn to Westminster City Council's policies.
Annexe and granny-flat drawings for Queen's Park — the model-cottage streets of the Queen's Park Estate on the Westminster side — planned to stay ancillary and drawn to Westminster City Council's policies.
Three similar buildings, three different consents. This is what separates them.
| What you build | Planning status | Key test | What Westminster City Council checks |
|---|---|---|---|
| Garden room, no sleeping space | Often Class E permitted development | Incidental to the house | Height, footprint, boundary position |
| Annexe used by the household | Full application, usually with a tie condition | Ancillary use | Shared garden and access, layout |
| Self-contained unit, own access | New dwelling — full application | Separate planning unit | Policy on new homes, amenity, parking |
| Converted garage or ground floor | Often permitted, use still assessed | Whether use changes | Independence of the accommodation |
| Annexe on designated land | Full application | Designation | Character and appearance |
The ancillary/separate-dwelling distinction comes from section 55 of the Town and Country Planning Act 1990; outbuilding limits from the GPDO 2015, Schedule 2, Part 1, Class E.
A fixed process built around how Westminster City Council tests the use question as well as the design.
Tell us who the annexe is for and where it would sit on the plot. We confirm designation status and tell you honestly whether the scheme reads as ancillary or as a separate dwelling in Westminster.
We measure the plot, the existing house and the access route, so the shared-garden and shared-access case can be drawn rather than asserted.
Chartered designers develop the annexe to your brief, with the layout, access and garden relationship arranged to support the ancillary case under Westminster City Council's policies.
We submit the application with a supporting statement on use, manage validation and case-officer queries, and revise free until Westminster City Council decides.
Almost always. Sleeping accommodation is generally not "incidental" to the enjoyment of a house, so it falls outside the outbuilding permitted-development right, and any annexe that could function independently raises a change-of-use question under section 55. In Westminster we prepare a full application to Westminster City Council and make the ancillary case explicitly rather than hoping it is not asked.
A shared garden rather than a divided one, access through the main property rather than a separate street entrance, occupation by a member of the same household, and a physical and functional relationship with the main house. Westminster City Council weighs those together — no single feature decides it, but a separate front door and a fenced-off garden together usually settle it against you.
Yes, subject to permission. A detached garden annexe is assessed on its scale against the plot, its effect on neighbours and the character of the area, and then on the use question. Keeping it single storey, set in from boundaries and served off the shared garden gives it the best prospect in Westminster, particularly near designated areas such as Bayswater and Maida Vale. Westminster City Council is the decision-maker.
Commonly, yes — a condition tying occupation of the annexe to the main dwelling, so it cannot be sold or let separately. That is normally what makes approval possible, because it removes the concern that a new independent home is being created without going through housing policy. The condition runs with the land, so it matters at resale, and we explain the implications before you commit. This applies to your Westminster address specifically. Westminster City Council is the decision-maker.
Yes. A new annexe is new habitable accommodation, so structure, fire escape, insulation and ventilation all apply, and a detached annexe close to a boundary raises fire-spread requirements as well. Planning and building control are separate consents with separate submissions — we prepare both so the approved design is the one that can actually be built. This applies to your Westminster address specifically. Westminster City Council is the decision-maker.
A householder application runs to an eight-week statutory target; where the council treats the annexe as creating a new unit it becomes a minor application with a thirteen-week target instead. Which route applies depends on how the use is characterised, which is precisely why the ancillary case is worth making properly at the outset. This applies to your Westminster address specifically. Westminster City Council is the decision-maker.
We quote each Westminster annexe individually, because plot, access and whether you are converting or building new all change the work, and send a fixed, no-obligation quote within one working day. It covers the full drawing pack and supporting statement, with free revisions until Westminster City Council approves. Call 020 7864 7245 to start.
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