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Slate-clad roof extension on a yellow-brick London terraced house
Photograph: Daniel Sikpi

01Bexley, London

Mansard roof drawings for Bexley houses

The first thing a Bexley officer compares a new mansard with is the other half of the pair, or the next house in the terrace. We draw both roofs in every elevation, so the comparison is on the sheet before anyone has to ask for it. Our fee starts at £845 including VAT.

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    02The brief

    The neighbouring roof sets the test

    75.3% of Bexley households live in a house or bungalow, so most roof enquiries here begin with a semi-detached pair or a short terrace. The council's Design and Development Control Guidelines ask that a roof extension stays within the existing ridge height, that dormers face the rear, and that the work sits back from the main wall so the house does not read as having gained a storey.

    A mansard has a flat crown and steep sides, which is a different shape from the pitched roof next door. For that reason the survey records the ridge, the eaves and the party wall line of both halves, and the proposed elevation lays the new profile over them.

    Converted loft bedroom with roof windows and a Juliet balcony
    Rear view of brick terraced houses in London with slate roofs and chimney stacks along the shared roofline
    Photograph: Ben Hadfield

    03The record

    Local figures for Bexley

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Class B, condition B.2(b)(i)(aa)Class B requires the original eaves to be maintained or reinstated, which a parapet-fronted mansard normally removesNo periodlegislation.gov.uk
    Class AA, para AA.1(c)Class AA additional storeys exclude houses built before 1 Jul 1948 or after 28 Oct 2018No periodlegislation.gov.uk
    Class AA, para AA.1(b)Class AA is not available on article 2(3) landNo periodlegislation.gov.uk
    Householder: alterations/extensions to a single dwellinghouse, from 1 Apr 2026548 GBPNo periodribblevalley.gov.uk
    Party Wall etc. Act 1996 s3(2)(a)Party structure notice at least 2 months before workNo periodlegislation.gov.uk
    Conservation areas23 named conservation areas published by the councilNo periodplanning.data.gov.uk
    Households living in a house75.3 % of households living in a house or bungalow (detached, semi-detached or terraced)Census 2021nomisweb.co.uk
    Householder decisions877 decisions1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder applications granted94.6 %1 July 2025 - 30 June 2026assets.publishing.service.gov.uk

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

    Bexley7 neighbouring councils
    Councils bordering Bexley

    04The streets

    Householder applications by street in Bexley

    Streets in Bexley with the most householder applications, and the share approved
    StreetApplicationsApproved
    Rydal Drive3688%
    Danson Road3578%
    Glenhurst Avenue3491%
    Westwood Lane3494%
    Wren Road3389%
    Harland Avenue3297%
    Halfway Street3167%
    Northumberland Avenue3197%
    Okehampton Crescent3090%
    Upton Road2679%
    Bellegrove Road2591%
    Latham Road25100%
    Mayplace Road East2584%
    Walton Road25100%
    Wansunt Road2596%

    Counts of householder applications by street; no individual applications are shown. Streets with fewer than five applications are left out.

    GLA Planning London Datahub, householder applications

    05The drawing

    A mansard roof in sectionA, Permitted development and the eaves: Class B requires the original eaves to be maintained or reinstated, which a parapet-fronted mansard normally removes. B, Additional storeys under permitted development: Class AA additional storeys exclude houses built before 1 Jul 1948 or after 28 Oct 2018. C, Fire protection to the stair: 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)ABC

    A mansard roof in section

    A London terrace with a mansard behind the parapet. The lettered marks show the limits the legend gives.

    A Permitted development and the eaves
    Class B requires the original eaves to be maintained or reinstated, which a parapet-fronted mansard normally removes
    B Additional storeys under permitted development
    Class AA additional storeys exclude houses built before 1 Jul 1948 or after 28 Oct 2018
    C Fire protection to the stair
    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)
    The mansard in three dimensions3D
    Scroll the page: the model turns with it.

    06The detail

    Why permitted development seldom reaches a mansard

    Class B is the usual loft route, and it has a snag for this roof form: Class B requires the original eaves to be maintained or reinstated, which a parapet-fronted mansard normally removes. A parapet-fronted mansard would need the application route instead.

    Class AA, which adds whole storeys, comes with its own conditions. Class AA additional storeys exclude houses built before 1 Jul 1948 or after 28 Oct 2018, and Class AA is not available on article 2(3) land.

    Conservation areas and listed houses

    The council designates 23 conservation areas, and in each of them a roof extension needs a householder application. The data we hold does not give a count of Article 4 directions for the borough, so the free constraints check reads your address against the live maps instead.

    The borough also holds 114 list entries. A listed house needs consent for roof work as well as planning permission, and listed building consent drawings in Bexley covers that second application.

    What the council has decided lately

    Bexley decided 877 householder applications in its latest published year, granted 94.6% and decided 99.4% on time. Those figures cover every kind of householder work, so they say little about a roof on its own.

    The council charges £548 for a householder application. If the roof is shared, the Party Wall etc. Act 1996 adds a notice to the neighbour: Party structure notice at least 2 months before work. Anyone also weighing a lower floor can read basement conversion drawings in Bexley, and mansard roof drawings in Barking and Dagenham shows how a neighbouring outer-London council sees the same roof.

    Planning sheet for a single-storey rear extension: proposed ground floor plan and rear elevation, with the Property Architecture title block
    Sample drawing. Proposed plan and rear elevation from a planning application set, sheet 03 at 1:50.

    07The papers

    What the drawings rest on

    Upper floors of a large yellow-brick Victorian house in London with chimney potsFlat conversions & change of use
    Photograph: Lorenc Memaga
    Loft floor plan marked up in an independent review, with three critical issues clouded and explained
    Sample drawing. A loft plan with the reviewer’s mark-up: stair pitch, dormer cheeks and roof ventilation.

    08Correspondence

    Questions

    Does a Bexley mansard have to stay below the existing ridge?

    Bexley's Design and Development Control Guidelines ask roof extensions to stay within the existing ridge height. If your design rises above it, we say so in the constraints check and show the ridge line on the elevation, so the case for the difference is clear.

    Could Class AA cover a Bexley house?

    Only a house inside the dates in the rule, and not on conservation land. The limits read: Class AA additional storeys exclude houses built before 1 Jul 1948 or after 28 Oct 2018, and Class AA is not available on article 2(3) land.

    Why does Bexley want dormers at the back?

    Its guidance asks for dormers to face the rear and for roof extensions to be set back from the main wall, which keeps the front elevation reading as the original house. A mansard is judged against the same idea.

    Brick cottage with a tiled roof, chimneys and a front dormer window

    94.6%

    Householder applications granted, Bexley, 1 July 2025 - 30 June 2026. Source: assets.publishing.service.gov.uk

    Photograph: Tanya Barrow

    09Further reading

    Other services in Bexley

    Mansard roof drawings nearby

    10Sources

    Sources and dates

    Licences

    Kensington street lined with brick townhouses and lit streetlamps beneath an orange dusk sky

    Send us the address of your house.

    We look up the conservation area, listing and Article 4 position, then reply with a fixed fee. A message before 3pm is answered the same working day.

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    Mansard roof drawings in Bexley