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

01Tower Hamlets, London

Mansard roof drawings in Tower Hamlets

One Tower Hamlets appraisal, for the York Square conservation area, objects to mansards on unified terraces. So we read the appraisal for your street before we draw a roof extension, and tell you plainly whether it is a realistic place for an extra storey.

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    02The brief

    What the York Square appraisal says about mansards

    The York Square Conservation Area character appraisal and management guidelines say that mansard extensions can destroy the scale and balance of a unified terrace. Its verdict on them is blunt: not suitable in most of area.

    That wording belongs to one conservation area, not the whole borough, and we hold no borough-wide mansard policy for Tower Hamlets. Any of the borough's 59 conservation areas may have its own appraisal or guidance, so we check what covers your street before quoting. Where it is silent on roofs, the general heritage tests still apply: see the mansard roof drawings hub for how we read them.

    Upper floors of a large yellow-brick Victorian house in London with chimney pots
    Converted loft bedroom with roof windows and a Juliet balcony
    Photograph: Imad Clicks

    03The record

    Local figures for Tower Hamlets

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Mansard extensions can destroy scale and balance of unified terraces and are unsuitable in most of the conservation areanot suitable in most of areaNo periodtowerhamlets.gov.uk, York Square Conservation Area Character Appraisal and Management Guidelines, Management guidelines, p.17
    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 areas59 named conservation areas published by the councilNo periodplanning.data.gov.uk
    Article 4 directions64 Article 4 directions published by the councilNo periodplanning.data.gov.uk
    Listed building entries916 list entries (Historic England, within the LPA boundary)No periodplanning.data.gov.uk
    Householder decisions191 decisions1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder applications granted92.7 %1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder applications decided in time95.8 % decided within 8 weeks or an agreed extended period1 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.

    Tower Hamlets6 neighbouring councils
    Councils bordering Tower Hamlets

    04The 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.

    05The detail

    Where the permitted development routes run out

    Two national routes might seem to help, and both usually fail on a period terrace. Class B requires the original eaves to be maintained or reinstated, which a parapet-fronted mansard normally removes. For a new storey, 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.

    Add the borough's 64 Article 4 directions and 916 list entries and the practical answer is a householder planning application for most roofs, with the council's householder fee of £548. Check listing before anything else: a listed house also needs consent, covered under listed building consent drawings in Tower Hamlets.

    Householder decisions across the borough

    In its latest figures the council decided 191 householder applications and granted 92.7% of them, with 95.8% decided within eight weeks or an agreed extension. Those figures cover all householder work, not mansards alone, so they show how the council handles applications and nothing about the odds for a roof.

    The drawings that go in with an application start at £845 including VAT, and the borough figures are background to that spend, not a forecast.

    Building regulations once the roof is agreed

    A new storey also has to pass Building Regulations. 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), and Party structure notice at least 2 months before work. A basement scheme at the same address brings its own rules: see basement conversion drawings in Tower Hamlets.

    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.

    06The papers

    What the drawings rest on

    Brick cottage with a tiled roof, chimneys and a front dormer windowLawful development certificates
    Photograph: Tanya Barrow
    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.

    07Correspondence

    Questions

    Can a mansard be built on a terrace in a Tower Hamlets conservation area?

    It depends on the appraisal for that area. The York Square guidance rates mansards not suitable in most of area. For other areas we read the relevant appraisal first and tell you if the street is unlikely to work.

    Is a mansard permitted development in Tower Hamlets?

    Rarely. Class AA is not available on article 2(3) land, and the eaves rule for a standard loft conversion usually rules out a parapet-fronted mansard. A planning application is the normal route.

    What do mansard roof drawings cost in Tower Hamlets?

    Our fee starts at £845 including VAT, fixed up front after a free constraints check. The council's fee for a householder application, £548, is paid to the council separately.

    Rear view of brick terraced houses in London with slate roofs and chimney stacks along the shared roofline

    92.7%

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

    Photograph: Ben Hadfield

    08Further reading

    Other services in Tower Hamlets

    Mansard roof drawings nearby

    09Sources

    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 Tower Hamlets