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Westminster, London

Double-storey extension drawings in Westminster

Double-storey extension drawings for a Westminster house start at £1,295 including VAT. A second storey is a planning application in practice: the borough has 56 conservation areas, and its roofs and mews guidance shapes what officers will accept on top of an existing building.

From £1,295 (VAT included)

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    Brick house being extended, with a wide new opening supported over the ground floor

    Westminster's guidance for double-storey extensions

    Westminster's design advice for upward and rear additions sits in two supplementary guides: the Roofs: a guide to alterations and extensions on domestic buildings SPG and the Mews: a guide to alterations SPG. The first deals with roofs and the way alterations change the profile of a building; the second deals with mews houses, the small buildings behind the main streets, where an extra floor is read against the lane as a whole. If your house is in a mews, we read the mews guide before we sketch anything.

    Both guides sit under the City Plan 2019-2040 (2026). In practice we read them before we draw. We test the massing of a double-storey scheme against the elevation of the whole row, not only the plot. We draw the street elevation with your neighbours on either side so the effect on the roofline is visible before anything is submitted.

    The national permitted development limit is rarely the answer in this borough: Over one storey: max 3 m beyond the original rear wall and not within 7 m of the rear boundary. Inside a conservation area the position is: No rear extension of more than one storey under PD on article 2(3) land.

    Finished white-rendered rear house extension with large glazed doors

    Local figures for Westminster

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Conservation areas56 named conservation areas published by the council—planning.data.gov.uk
    Article 4 directions10 Article 4 directions published by the council—planning.data.gov.uk
    Tree preservation orders685 tree preservation orders published by the council—planning.data.gov.uk
    Listed building entries4,015 list entries (Historic England, within the LPA boundary)—planning.data.gov.uk
    Householder decisions366 decisions1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder applications granted82 %1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder applications decided in time79 % decided within 8 weeks or an agreed extended period1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Supplementary planning documentRoofs: a guide to alterations and extensions on domestic buildings SPG—westminster.gov.uk
    Supplementary planning documentMews: a guide to alterations SPG—westminster.gov.uk
    Class A, para A.1(h)Over one storey: max 3 m beyond the original rear wall and not within 7 m of the rear boundary—legislation.gov.uk
    Class A, para A.2(c)No rear extension of more than one storey under PD on article 2(3) land—legislation.gov.uk
    Approved Document B Vol 1, 2019 ed. incl. 2026 amendments, para 2.10Escape window: unobstructed openable area at least 0.33 m², at least 450 mm high and 450 mm wide, bottom of opening no more than 1100 mm above floor—gov.uk

    A blank value means the figure has not been published, not that there are none. Check your own address with the council.

    Councils bordering Westminster

    Householder applications by street in Westminster

    Streets in Westminster with the most householder applications, and the share approved
    StreetApplicationsApproved
    Randolph Avenue1679%
    Ashworth Road1385%
    Clifton Hill1170%
    Ponsonby Place10100%
    Lancaster Mews938%
    Westbourne Park Road988%
    Carlton Hill886%
    Kilburn Lane886%
    Sutherland Place863%
    Wilton Row8100%
    Caroline Close733%
    Chester Row7100%
    Greenberry Street757%
    Hereford Road760%
    Hyde Park Gardens Mews775%
    Counts of householder applications by street; no individual applications are shown. Streets with fewer than five applications are left out.Source: GLA Planning London Datahub, householder applications, all years held. Contains public sector information licensed under the Open Government Licence v3.0. Contains OS data © Crown copyright and database right 2026.
    The 45-degree test in planTest used in daylight assessments: 45 degrees (plan and elevation)A

    The 45-degree test in plan

    A line from the middle of the neighbour's nearest window: the extension should stay behind it.

    A · Test used in daylight assessments
    45 degrees (plan and elevation)

    Protected land is the rule, not the exception

    Westminster has 10 Article 4 directions, 685 tree preservation orders and 1 World Heritage Site in the borough. Historic England lists 4,015 entries inside the boundary, and 205 of them are Grade I. We check each one against your address.

    A listed house needs listed building consent for an extension, with drawings that show the existing fabric and what the new work does to it. A tree preservation order affects where foundations can go, which matters when a second storey needs heavier support below. We map all of it on your plot before we propose a design.

    How Westminster decides householder applications

    In its latest published year Westminster decided 366 householder applications and granted 82 per cent. Only 79 per cent were decided within eight weeks or an agreed extension, so plan for the process to run beyond the statutory period.

    Those figures cover all householder work, from windows to extensions, and say nothing about a particular house. We use the numbers to set realistic timing, never to predict a result.

    Upper floors, fire and party walls

    Two technical rules shape the upper floor of any double-storey scheme. Side windows on an upper floor need: Upper-floor side windows obscure-glazed and non-opening below 1.7 m above floor. A first-floor bedroom needs a way out: Escape window: unobstructed openable area at least 0.33 m², at least 450 mm high and 450 mm wide, bottom of opening no more than 1100 mm above floor.

    Where your house shares a wall with a neighbour, the Party Wall Act applies. Notice for work to a party structure is: Party structure notice at least 2 months before work. Where new foundations come close to a neighbour: Adjacent excavation notice at least 1 month before work: within 3 m and deeper than the neighbour's foundations, or within 6 m and cutting a 45° line from their foundations. Our party wall notices service prepares them.

    What you receive and what it costs

    Our drawings start at £1,295, VAT included, agreed before work begins. You receive plans of both floors, elevations, sections and the location and block plans, each sheet checked by a second chartered technologist. The council's householder fee is £548, paid separately.

    If officers ask for changes, we redraw at no charge until approval. Where your scheme needs planning permission, our planning drawings page explains what the application includes.

    Other drawings in Westminster and nearby

    Start from architectural drawings in Westminster for the borough overview. Rear extension drawings in Westminster cover a lower, single-storey addition, and loft conversion drawings in Westminster suit a roof-level gain. The full national rules are on the double-storey extension drawings hub. Neighbouring boroughs: Camden, Kensington and Chelsea and Lambeth.

    What you receive

    Planning drawing sheet for a rear extension with plans, elevations and sections
    Sample drawing. Planning drawings for a rear extension: plans, elevations and sections on one sheet set.
    Two-storey rear extension under construction on a semi-detached house
    Every side considered
    Flick across the turntable to spin it.

    Other services in Westminster

    Double-storey extension drawings nearby

    Questions

    Can I add a second storey to a mews house in Westminster?

    Expect to need planning permission, and the council's mews guidance applies. We draw the new storey against the whole lane so its effect is clear.

    How many conservation areas does Westminster have?

    56, and 10 Article 4 directions. We check both for your address before suggesting a route.

    Is permitted development available for a two-storey extension here?

    Rarely. The national limit is: Over one storey: max 3 m beyond the original rear wall and not within 7 m of the rear boundary, and it does not apply in conservation areas.

    How much do double-storey extension drawings cost in Westminster?

    From £1,295 including VAT, fixed up front.

    Sources and dates

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    Tell us about your property.

    We check the constraints, then send a fixed fee. Messages before 3pm get a reply the same working day.

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