Westminster, London
Dormer loft conversion drawings in Westminster
Dormer loft conversion drawings for a Westminster house start at £695 including VAT. With 56 conservation areas and 4,015 listed entries, heritage rules decide the route for many roofs, and the council's Roofs guidance decides how a dormer is judged.
From £695 (VAT included)
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- £2m PI insured
- LABC Partnered
- Fixed fees, VAT included
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Westminster's Roofs guidance and dormers
The council's reference for roof work is the Roofs: a guide to alterations and extensions on domestic buildings SPG, backed by the City Plan 2019-2040 (2026). The guide covers how many dormers a roof can take and where they go, and it is the document a roof application is judged against.
Where a house has a mansard roof, the guide says the windows should be dormers in the steep principal slopes only, set behind the parapet, with their tops below the knee of the roof. We apply the same reading to other roofs: the dormer must read as a small, subordinate window in the roof, not a new storey.
For the mews and back-street houses that make up part of the borough, the council also publishes the Mews: a guide to alterations SPG. We read both guides against your house before drawing, because the answer depends on whether the property is a terrace house or a mews.
Local figures for Westminster
| Measure | Value | Period | Source |
|---|---|---|---|
| Conservation areas | 56 named conservation areas published by the council | — | planning.data.gov.uk |
| Article 4 directions | 10 Article 4 directions published by the council | — | planning.data.gov.uk |
| Listed building entries | 4,015 list entries (Historic England, within the LPA boundary) | — | planning.data.gov.uk |
| Householder decisions | 366 decisions | 1 July 2025 - 30 June 2026 | assets.publishing.service.gov.uk |
| Householder applications granted | 82 % | 1 July 2025 - 30 June 2026 | assets.publishing.service.gov.uk |
| Householder applications decided in time | 79 % decided within 8 weeks or an agreed extended period | 1 July 2025 - 30 June 2026 | assets.publishing.service.gov.uk |
| Supplementary planning document | Roofs: a guide to alterations and extensions on domestic buildings SPG | — | westminster.gov.uk |
| Local plan | City Plan 2019-2040 (2026) | — | westminster.gov.uk |
| GPDO 2015 Sch 2 Pt 1 Class B, para B.1(d) | 40 m³ (terrace house) / 50 m³ (any other house) additional roof volume | — | legislation.gov.uk |
| Class B, para B.1(c) | No enlargement beyond the plane of a roof slope that forms the principal elevation and fronts a highway | — | legislation.gov.uk |
| Class B, para B.1(f) | Class B roof enlargements are not permitted development on article 2(3) land | — | legislation.gov.uk |
A blank value means the figure has not been published, not that there are none. Check your own address with the council.
Householder applications by street in Westminster
| Street | Applications | Approved |
|---|---|---|
| Randolph Avenue | 16 | 79% |
| Ashworth Road | 13 | 85% |
| Clifton Hill | 11 | 70% |
| Ponsonby Place | 10 | 100% |
| Lancaster Mews | 9 | 38% |
| Westbourne Park Road | 9 | 88% |
| Carlton Hill | 8 | 86% |
| Kilburn Lane | 8 | 86% |
| Sutherland Place | 8 | 63% |
| Wilton Row | 8 | 100% |
| Caroline Close | 7 | 33% |
| Chester Row | 7 | 100% |
| Greenberry Street | 7 | 57% |
| Hereford Road | 7 | 60% |
| Hyde Park Gardens Mews | 7 | 75% |
Loft enlargement in section: the permitted development limits
A dormer on the rear slope, with the limits that decide whether it needs planning permission.
- A · Extra roof volume allowed
- 40 m³ (terrace house) / 50 m³ (any other house) additional roof volume
- B · Set-back from the eaves
- Original eaves maintained; enlargement set at least 0.2 m from the eaves measured up the roof slope, so far as practicable (not required for hip-to-gable or roofs joining a rear/side extension)
- C · Height limit
- No part higher than the highest part of the existing roof
Conservation areas, Article 4 and listing in Westminster
Westminster has 56 conservation areas and 10 Article 4 directions. Inside a conservation area a roof enlargement is not permitted development, so a dormer is always a planning application there.
Historic England records 4,015 listed entries in the borough, and the borough contains 1 World Heritage Site. A listed house needs listed building consent for roof changes as well as planning permission, and the heritage case can matter more than the geometry.
That is why the first step is an address check, and why we ask for photographs of the roof from the street and from the rear before we quote. If the house keeps its permitted development rights, the volume allowance is 40 m³ (terrace house) / 50 m³ (any other house) additional roof volume. If it does not, we draw for a planning application from the start and save you a second round.
Westminster householder decisions
Westminster decided 366 householder applications in its latest published year and granted 82 per cent. 79 per cent were decided within the statutory period or an agreed extension.
The figures cover every kind of householder project. They are a guide to timing, not to the outcome of a particular dormer.
We build the timetable around the decision period, and we tell you early if heritage advice or a pre-application discussion would help.
Materials and windows are where heritage officers look hardest. Under permitted development the exterior finish must be Exterior materials similar in appearance to the existing house, and upper-floor side windows must be Upper-floor side windows obscure-glazed and non-opening below 1.7 m above floor. In a conservation area those become design choices we justify on the elevations, not conditions we simply meet.
What a Westminster dormer loft conversion drawing set includes
The set shows existing and proposed floor plans, the stair, the roof in section with the dormer and its build-up, and every elevation, with the location and block plans. On a heritage property we also annotate the materials and joinery so that the officer sees the detail without a separate sheet.
The stair follows the loft rule in the building regulations: Loft conversions where 2.0 m cannot be achieved: 1.9 m at the centre of the stair, 1.8 m at the side (half width). A new storey above the stated height needs a protected escape route: New storey above 4.5 m by loft conversion: protect the full escape route with fire-resisting doors (min E 20) and partitions (min REI 30). Both appear on the plans and in the specification. The new dormer roof also has an insulation target: New elements in existing dwellings, limiting U-values W/(m²·K): roof 0.15, wall 0.18, floor 0.18, windows 1.4 (or WER Band B), doors 1.4.
The price is £695 including VAT, fixed before you commit. A second MCIAT chartered architectural technologist checks every sheet, and we redraw at no charge if the council asks for changes.
More on roofs in Westminster and nearby
For other roof forms, see loft conversion drawings in Westminster and Velux loft conversion drawings in Westminster for rooflights only. A rear addition is covered by rear extension drawings in Westminster.
Next to Westminster, the tests differ: dormer loft conversion drawings in Camden, in Kensington and Chelsea and in Lambeth. The borough overview is architectural drawings in Westminster, and the national rules are on the dormer loft conversion drawings hub.
What you receive
Related pages
Other services in Westminster
Dormer loft conversion drawings nearby
Questions
Can I build a dormer in a Westminster conservation area?
It needs planning permission, because the permitted development right for roof enlargements does not apply there. Whether it is accepted depends on the Roofs guidance and on the character of the area.
Which Westminster guidance covers dormers?
The Roofs guide to alterations and extensions on domestic buildings, supplementary planning guidance. For mews houses there is also a separate Mews guide.
Is a listed house in Westminster different?
Yes. It needs listed building consent for roof changes as well as planning permission, and the drawings and heritage case differ.
What do dormer loft conversion drawings cost in Westminster?
From £695 including VAT, fixed up front. Council fees are separate.
Sources and dates
- planning.data.gov.uk, retrieved
- planning.data.gov.uk, retrieved
- planning.data.gov.uk, retrieved
- assets.publishing.service.gov.uk, retrieved
- westminster.gov.uk, retrieved
- westminster.gov.uk, retrieved
- legislation.gov.uk, retrieved
- planning.data.gov.uk, retrieved
- gov.uk, retrieved
- gov.uk, retrieved
- gov.uk, retrieved
- Contains public sector information licensed under the Open Government Licence v3.0.
- Contains OS data © Crown copyright and database right 2026.
- Contains HM Land Registry data © Crown copyright and database right 2026. This data is licensed under the Open Government Licence v3.0.
- Contains Historic England data © Historic England 2026. Contains Ordnance Survey data © Crown copyright and database right 2026.
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