Rear Dormer Loft Conversion Westminster | SW1

What's included

Fully end-to-end in Westminster.

PD eligibility check

The Permitted Development check comes first, though here it often ends quickly. Allowances are volumes stated in cubic metres, never square: 40 if the house sits in a terrace, ten more than that if it is semi-detached or detached. After that comes Article 4 status, conservation area designation, and whatever previous extensions have already used up.

LDC or planning application

Where the rights survive, we obtain a Lawful Development Certificate so that nobody has to take your word for it in five years. Where they do not, the route is a full application to Westminster City Council with a design and access statement.

Dormer design & massing

Flat-roofed, full width, materials matched to the roof it joins, held clear of both party walls, cheeks clad and not rendered. That gives an officer least to argue with, and in this city the argument is nearly always with an officer rather than a committee: 14,141 of 14,408 decisions across the twelve published quarters, or 98.1%, were taken under delegated powers, against 97.0% London-wide. Source: MHCLG live planning statistics

Building Regulations package

Part B fire escape (protected staircase, fire doors, smoke alarms), Part K staircase, Part L insulation, Part E acoustic separation.

Structural engineering

The structure is designed and signed by a chartered engineer: ridge beam, purlin support, the dormer frame itself, and whatever the floor joists need in order to carry a room.

Party Wall coordination

Where a steel bears into the party wall, the Act is engaged at section 2 and the notice you serve is a section 3 notice. Section 6 is for excavation close to a neighbour's foundations, which a loft seldom involves. Almost every Westminster dormer engages one of the two, and we draft and serve whichever it is.

Which Westminster postcodes does this rear dormer service cover?

A district-by-district list for Westminster: what stands in each one, and which authority decides an application from it. Fees below are 2026 statutory England rates, paid to the council and separate from anything we charge.

Postcode	Area	Dominant stock	What it means for a rear dormer
W1U	Marylebone	Georgian terraces, Edwardian mansion blocks	W1U is Marylebone, decided by Westminster City Council under the borough's Local Plan policies.
W1W	Fitzrovia / Great Portland Street	Grand Georgian and Regency terraces in Belgravia and Pimlico; Victorian and Edwardian mansion blocks; heritage-rich townhouses throughout; very high listed building density	Fitzrovia and Great Portland Street fall inside W1W, wholly within the city, so Westminster validates everything from that district.
W2	Bayswater / Paddington	Victorian stucco terraces	W2 is Bayswater and Paddington, wholly Westminster, so the city council validates every application coming from it.
W9	Maida Vale	Victorian terraces, mansion blocks	W9 is Maida Vale, entirely Westminster, and its case officers apply the W9 conservation-area boundaries.
WC2B	Covent Garden / Holborn	Grand Georgian and Regency terraces in Belgravia and Pimlico; Victorian and Edwardian mansion blocks; heritage-rich townhouses throughout; very high listed building density	WC2B runs between Covent Garden and Holborn across the Camden boundary, so the policies map, not the postcode, names the authority.
WC2E	Covent Garden	Georgian terraces, conversions	WC2E is Covent Garden proper, determined by Westminster City Council against its own Local Plan.
WC2H	Covent Garden / Leicester Square	Georgian terraces, conversions	WC2H takes in Covent Garden and Leicester Square and lies entirely with Westminster City Council.
WC2N	Charing Cross / Strand	Grand Georgian and Regency terraces in Belgravia and Pimlico; Victorian and Edwardian mansion blocks; heritage-rich townhouses throughout; very high listed building density	WC2N covers Charing Cross and the Strand, wholly Westminster, with the district conservation-area map governing what is possible.

What changes about a rear dormer in each part of Westminster?

Roof pitch, wall construction and what sits behind the parapet can all change between two Westminster streets, and each of them changes what a rear dormer can be at that address.

Pimlico (SW1V) — rear dormer work in Pimlico means regency terraces, post-war estates. Pimlico is Regency stucco terraces, grid plan. Trussed post-war roofs need a full structural redesign before a dormer throughout SW1V. Westminster City Council decides the Pimlico application, and Tate Britain anchors the Pimlico location plan.
Soho (W1D, W1F) — Georgian fragments, mixed-use defines Soho, where georgian terraces, mixed-use set what a rear dormer can do. A dormer on a Georgian roof has to sit behind the parapet line to stand any chance of consent across W1D. Any Soho rear dormer is validated by Westminster City Council, with Soho Square the usual Soho reference point on the site plan.
Covent Garden (WC2E, WC2H) — Georgian piazza, listed buildings defines Covent Garden, where georgian terraces, conversions set what a rear dormer can do. A dormer on a Georgian roof has to sit behind the parapet line to stand any chance of consent across WC2E. Any Covent Garden rear dormer is validated by Westminster City Council, with Royal Opera House the usual Covent Garden reference point on the site plan.
St John's Wood (NW8) — a rear dormer in St John's Wood starts from victorian villas, mansion blocks, and St John's Wood reads as Victorian villas, mansion blocks. Full-width rear dormers on Victorian terraces here are the default in NW8. Westminster City Council assesses St John's Wood rear dormers against its own St John's Wood character guidance, and the location plan we draw for St John's Wood references Lord's Cricket Ground.
Bayswater (W2) — a rear dormer in Bayswater starts from victorian stucco terraces, and Bayswater reads as Victorian stucco terraces. Full-width rear dormers on Victorian terraces here are the default in W2. Westminster City Council assesses Bayswater rear dormers against its own Bayswater character guidance, and the location plan we draw for Bayswater references Hyde Park.
Paddington (W2) — a rear dormer in Paddington starts from regency terraces, modern apartments, and Paddington reads as Regency and Victorian terraces, canal-side regen. Shallow modern roof pitches rarely leave the head height a dormer needs in W2. Westminster City Council assesses Paddington rear dormers against its own Paddington character guidance, and the location plan we draw for Paddington references Paddington Basin.
Victoria (SW1E, SW1W) — rear dormer work in Victoria means regency terraces, post-war flats. Victoria is Regency terraces, mixed-use. Trussed post-war roofs need a full structural redesign before a dormer throughout SW1E. Westminster City Council decides the Victoria application, and Victoria Station anchors the Victoria location plan.

What local planning policy applies to a rear dormer in Westminster?

How designation changes a Westminster rear dormer: Westminster City Council maintains 56 conservation areas, including Soho, Covent Garden, St John's Wood. Inside any of them a Westminster rear dormer cannot rely on permitted development, and the route becomes a £548 householder application determined in 8 weeks rather than a £249 prior approval in 6 weeks. Belgravia sets the tone for Westminster casework.

What Article 4 removes near Westminster: Multiple Article 4 Directions — office-to-residential restrictions, HMO conversions, retail to residential in shopping zones. Before pricing a rear dormer we check whether the NW8 address is inside the mapped area, because Westminster City Council draws the Westminster boundary street by street rather than across the whole of Westminster.

Digging below a Westminster property: Westminster basement policy restricts to single-storey, typically under 50% of rear garden footprint; lightwells and rooflights strictly controlled in conservation areas. Where a rear dormer in Westminster involves excavation that is read beside the Party Wall etc. Act 1996, which needs two months notice for a Westminster dig within 3 m of a neighbour, and Westminster City Council expects the NW8 ground conditions addressed in the application.

The building fabric around Westminster: Grand Georgian and Regency terraces in Belgravia and Pimlico; Victorian and Edwardian mansion blocks; heritage-rich townhouses throughout; very high listed building density. Heritage-first planning approach; listed buildings on almost every street; basement and rear extension policies particularly strict. A rear dormer in Westminster 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 Westminster City Council.

What happens if a Westminster property sits on a boundary?

Camden — cross the Westminster boundary and Camden Council takes the rear dormer instead, applying 40 conservation areas of its own around NW1. We re-price rear dormers at the Westminster edge because Camden policy and Westminster policy rarely align on rear dormer depth.
Kensington and Chelsea — cross the Westminster boundary and RBKC Planning takes the rear dormer instead, applying 38 conservation areas of its own around SW1. We re-price rear dormers at the Westminster edge because Kensington and Chelsea policy and Westminster policy rarely align on rear dormer depth.
Wandsworth — cross the Westminster boundary and Wandsworth Council takes the rear dormer instead, applying 45 conservation areas of its own around SW8. We re-price rear dormers at the Westminster edge because Wandsworth policy and Westminster policy rarely align on rear dormer depth.
Lambeth — adjoining Westminster, with 64 conservation areas centred on SE1. A rear dormer on the far side of the Westminster line is determined by Lambeth Council, so the Westminster quote for rear dormers is checked against Lambeth guidance before it is issued.

Sources for this Westminster rear dormer 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.

Westminster FAQs

Rear Dormer Loft Conversions in Westminster — your questions answered.

Direct answers on rear dormer drawings in Westminster, beginning with the question that matters most here: whether Permitted Development is available at your address at all.

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Do I need planning permission for a rear dormer in Westminster?

It depends on the address, and in Westminster the answer is frequently no. The national allowances are volumes: 40 cubic metres added on a terrace, 50 on a semi — cubic, not square, a distinction worth getting right — with the materials matched and a 20cm gap left at the eaves. Westminster then layers Article 4 Directions on top of that. Flats are outside the rights entirely, so are listed buildings, and so is anything inside a conservation area; all of them need planning permission. Between them they account for a great deal of the housing here: 44.1% of the city's 132,190 dwellings were built before 1900. Each condition is checked at the free feasibility visit rather than assumed.

How much does a rear dormer loft conversion cost in Westminster?

Two cost lines, and only the first is ours. Drawings, building regulations and structural calculations come as one fixed figure. The build belongs to the contractor and moves with access — which in central Westminster can mean permits, restricted hours and nowhere to stand a skip — with floor area, and with specification.

How much space does a rear dormer add in Westminster?

A full-width rear dormer yields something in the order of 15 to 25 square metres: one double bedroom with an en-suite, or two smaller rooms. What you are buying is standing height across the whole width, which a rooflight scheme cannot deliver because it leaves the original pitch exactly as it is.

Can I have a rear dormer in a conservation area in Westminster?

Conservation designation removes the rights, so a rear dormer across most of Westminster needs full planning permission. Its saving grace is orientation. A rear dormer is not seen from the street, and street impact is where the heritage judgement mostly lands, so it starts from a better position than a front dormer or a mansard ever will.

How long does a rear dormer take to build in Westminster?

A standard rear dormer occupies the builder for 8 to 12 weeks. Our drawings need 3 to 5 weeks before they can go in, Building Control adds 2 to 4 on top of that, and survey to moving back in is nearer 4 to 5 months.

Rear Dormer Loft Conversion Drawings in Westminster

What is a rear dormer drawings package in Westminster?

Quick facts · Rear Dormer Loft Conversions in Westminster

How does planning policy in Westminster affect your rear dormer drawings?