Kensington and Chelsea's most space-efficient loft solution when PD-route dormers are blocked. Our chartered team designs mansards that get approved in Kensington and Chelsea conservation areas — with heritage statements and planning officer negotiation built in.
Mansard roof extensions in Kensington and Chelsea, a borough of Grand white stucco Regency and Victorian terraces; red-brick Queen Anne mansions in Kensington; Edwardian mansion blocks; almost no post-war housing stock, are the full measured-survey-to-submission drawing set Royal Borough of Kensington and Chelsea needs in order to determine an application: existing and proposed plans, elevations and sections at 1:100 and 1:50, a location and site plan, and the supporting statements the case officer asks for.
Prepared and reviewed by the chartered technologist team at Architectural Drawings London — MCIAT chartered, £2m PI insured.Last reviewed 2026-08-03.
Kensington and Chelsea's most space-efficient loft solution when PD-route dormers are blocked. Our chartered team designs mansards that get approved in Kensington and Chelsea conservation areas — with heritage statements and planning officer negotiation built in.
Housing stock in Kensington and Chelsea: Grand white stucco Regency and Victorian terraces; red-brick Queen Anne mansions in Kensington; Edwardian mansion blocks; almost no post-war housing stock.
Character: Internationally wealthy residents; extensive listed building coverage; heritage and streetscape prioritised in every decision.
Article 4: Article 4 Directions covering HMOs, office-to-residential, and basement developments — RBKC has some of the strictest basement policies in London.
Basement policy: RBKC's basement policy (post-2015) limits to single-storey under 50% of garden area; double-storey basements effectively prohibited in residential streets.
We check against RBKC Planning's mansard design guide and design to match the terrace.
Required for Kensington and Chelsea's conservation areas — demonstrates the mansard respects character and townscape.
Accurate photomontage showing how the mansard sits alongside neighbours — often decisive at RBKC Planning committee.
Mansards invariably trigger Party Wall notices in Kensington and Chelsea's dense terraced streets. Structural package includes new ridge, tie beams, floor joists.
Full liaison with RBKC Planning planning officer, committee representation if called in.
Part L thermal, Part B fire (critical on mansards), Part E acoustic separation.
Single planning or regs submission.
Planning + building regs + structural.
Listed, conservation, complex sites.
Move the controls for an indicative figure. It anchors your budget — it is not a quote. Every project is priced after a free survey.
Build costs are separate and quoted by your contractor. See our published fees.
Every Kensington and Chelsea postcode district we draw in, the stock that dominates it and the authority that validates a mansard roof extension there. Kensington and Chelsea fees below are the statutory England rates for 2026, not mansard roof extension estimates.
| Postcode | Area | Dominant stock | What it means for a mansard roof extension |
|---|---|---|---|
| SW10 | West Brompton / World's End | Georgian and Victorian terraces, listed buildings | West Brompton / World's End is split at SW10. Either RBKC Planning or Hammersmith & Fulham Council can determine a mansard roof extension here, so the SW10 address is checked against both policies maps first. |
| W8 | Kensington | Stucco terraces, listed buildings | W8 covers Kensington only; RBKC Planning handles the mansard roof extension, and Kensington case officers apply the W8 conservation-area map. |
| W10 | North Kensington / Ladbroke Grove | Victorian terraces, post-war estates | North Kensington / Ladbroke Grove sits wholly inside W10, so RBKC Planning validates every mansard roof extension submitted from an W10 address. |
| W11 | Notting Hill / Holland Park | Victorian stucco terraces | W11 covers Notting Hill / Holland Park only; RBKC Planning handles the mansard roof extension, and Notting Hill / Holland Park case officers apply the W11 conservation-area map. |
| SW1X | Knightsbridge / Belgravia | Regency stucco terraces, listed buildings | SW1X straddles a boundary: Knightsbridge / Belgravia addresses fall to Westminster City Council or RBKC Planning, so confirm which authority validates the mansard roof extension before submitting SW1X drawings. |
| W14 | West Kensington / Barons Court | Victorian and Edwardian villas | W14 straddles a boundary: West Kensington / Barons Court addresses fall to Hammersmith & Fulham Council or RBKC Planning, so confirm which authority validates the mansard roof extension before submitting W14 drawings. |
| SW3 | Chelsea / Brompton | Georgian and Victorian terraces, listed buildings | SW3 covers Chelsea / Brompton only; RBKC Planning handles the mansard roof extension, and Chelsea / Brompton case officers apply the SW3 conservation-area map. |
| SW5 | Earl's Court | Stucco terraces, Edwardian mansion blocks | Earl's Court sits wholly inside SW5, so RBKC Planning validates every mansard roof extension submitted from an SW5 address. |
Roof pitch, wall build-up and plot depth change every few Kensington and Chelsea streets, and each one changes what a mansard roof extension can achieve at that address.
Kensington and Chelsea conservation designations: there are 38 across RBKC Planning, Kensington, Chelsea, Notting Hill among them. Designation costs a Kensington and Chelsea owner the permitted-development route: a mansard roof extension then needs a £548 householder application over 8 weeks, in place of the £249 prior approval route that takes 6 weeks. Chelsea is the Kensington and Chelsea designation that most often changes a mansard roof extension design.
Article 4 and your Kensington and Chelsea mansard roof extension: Article 4 Directions covering HMOs, office-to-residential, and basement developments — RBKC has some of the strictest basement policies in London. At a SW3 address that matters twice over, because RBKC Planning applies the direction unevenly across Kensington and Chelsea — we read the Kensington and Chelsea policies map for the exact SW3 address before quoting mansard roof extensions.
Digging below a Kensington and Chelsea property: RBKC's basement policy (post-2015) limits to single-storey under 50% of garden area; double-storey basements effectively prohibited in residential streets. Where a mansard roof extension in Kensington and Chelsea involves excavation that is read beside the Party Wall etc. Act 1996, which needs two months notice for a Kensington and Chelsea dig within 3 m of a neighbour, and RBKC Planning expects the SW3 ground conditions addressed in the application.
The building fabric around Kensington and Chelsea: Grand white stucco Regency and Victorian terraces; red-brick Queen Anne mansions in Kensington; Edwardian mansion blocks; almost no post-war housing stock. Internationally wealthy residents; extensive listed building coverage; heritage and streetscape prioritised in every decision. A mansard roof extension in Kensington and Chelsea is scoped against that stock first, because it decides whether the scheme runs as permitted development, a £274 Lawful Development Certificate, or a full £548 application to RBKC Planning.
Sources for this Kensington and Chelsea mansard roof extension page: borough policies maps and conservation-area registers (2025–26), Royal Mail postcode district boundaries, the Town and Country Planning (Fees for Applications) (England) Regulations, the Town and Country Planning (General Permitted Development) (England) Order 2015 as amended, and the Party Wall etc. Act 1996.
Of 139 listed building and conservation area consent appeals decided in Kensington and Chelsea over the window covering appeals decided 2016-2026, an appeal against Kensington and Chelsea succeeded more often than the London norm — 38.1% against 28.5% city-wide. 53 were allowed and 80 dismissed, with 6 split. Mansards concentrate on terraces in conservation areas and on listed buildings, where consent runs separately from planning permission. These 139 Kensington and Chelsea consent appeals are the contested minority.
Half of those Kensington and Chelsea appeals took more than 118 days to decide from the day the appeal started — time added on top of the council's own determination period, which is the argument for getting the application right first. 15.1% of them (21 cases) involved a conservation area, so heritage argument carries real weight in Kensington and Chelsea. 15.1% affected the setting of a listed building. 89.2% were decided by written representations rather than a hearing or inquiry, meaning the written case and the drawings were the whole of the evidence.
139 listed building and conservation area consent appeals decided in Kensington and Chelsea. Source: Planning Inspectorate casework, OGL v3.0.
Direct answers to the questions Kensington and Chelsea homeowners ask every week about mansard roof extensions.
Start a free quote →Mansards in Kensington and Chelsea are more heavily scrutinised than in outer boroughs. RBKC Planning prioritises heritage and townscape — approvals require exceptional design quality, clear precedents on the street, and a full Heritage Statement. We've delivered mansard approvals in the borough; each application is bespoke.
A 70° front slope is typical for Kensington and Chelsea mansards — steep enough to maximise floor area while reading as a roof rather than a full additional storey. Front dormers should be small and symmetrical. RBKC Planning's design guide (where published) takes precedence on detail.
Often yes, but RBKC Planning favours applications supported by wider street precedents. Where mansards already exist nearby in Kensington and Chelsea, approval is far more likely. We review street precedents at the feasibility stage.
A Kensington and Chelsea mansard carries more design work than a dormer — heritage statement, street-elevation massing and conservation-led detailing on top of planning, building regulations and structural calculations. Build cost then varies with size, roof geometry and site access. Our design fee is fixed before we start; see our fees.
Full-height — typically 2.3–2.5m ceiling from the new floor. Unlike a dormer, which gives partial head height, a mansard provides a complete additional storey within Kensington and Chelsea's grand white stucco Regency and Victorian terraces terraced context.
We cover all Kensington and Chelsea postcodes — SW1, SW3, SW5, SW7, SW10, W8, W10, W11, W14 — and have submitted mansard applications across the borough. Our heritage statement and design-and-access statement are included in every mansard package.
Kensington and Chelsea's grand white stucco Regency and Victorian terraces terraced stock is the natural context for mansard extensions — they were originally designed for Victorian and Edwardian rows. Feasibility depends on street precedent, conservation area status and party wall implications. We assess all three at the free site visit.
A mansard adds a full upper storey — typically 35–45m² of usable floor space. In Kensington and Chelsea this often converts a 3-bed house to 4 or 5 beds. The steep front slope (70°) and flat top read as a roof, not a full floor, which is why RBKC Planning accepts them more readily than a simple box extension.
If your property sits on a boundary, here are the neighbouring options.
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