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

01Sutton, London

Mansard roof drawings for Sutton houses

Sutton's extensions guidance leaves little room for a mansard on a house slope. It will not accept a mansard-type form on a pitched rear slope, and it resists dormers on front slopes where they are not part of the street. It does set out how a dormer should look, below the ridge and not across the whole slope. Our chartered architectural technologists (MCIAT) draw to those tests from £845 including VAT.

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    02The brief

    What the Design of Residential Extensions SPD says

    The Design of Residential Extensions SPD gives the rear and front tests in separate paragraphs. At the rear, turning a conventional pitched slope into a mansard-type form is not acceptable. At the front, dormers are front dormers resisted where they are not characteristic, especially on terraces and semis.

    For dormers the test is shape: below ridge; not full slope, away from the hip and behind the main elevation, with narrow cheeks. Hip-to-gable and half-hip changes are not encouraged, particularly where they upset the symmetry of a semi-detached pair.

    Brick cottage with a tiled roof, chimneys and a front dormer window
    Upper floors of a large yellow-brick Victorian house in London with chimney pots
    Photograph: Lorenc Memaga

    03The record

    Local figures for Sutton

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Converting a conventional pitched rear slope into a mansard-type form is not acceptablerear mansard not acceptableNo periodsutton.gov.uk, SPD4 Design of Residential Extensions (adopted October 2006), Appendix A, para A.5.7, p.24
    Front dormers resisted where not characteristic, particularly on terraces and semisfront dormers resistedNo periodsutton.gov.uk, SPD4 Design of Residential Extensions (adopted October 2006), para A.5.3, p.23
    Dormers set below ridge, away from hip, behind main elevation, not covering whole slope, with narrow cheeksbelow ridge; not full slopeNo periodsutton.gov.uk, SPD4 Design of Residential Extensions (adopted October 2006), para A.5.4, p.23
    Hip-to-gable or half-hip changes not encouraged, especially where they upset symmetry of a semi-detached pairnot encouragedNo periodsutton.gov.uk, SPD4 Design of Residential Extensions (adopted October 2006), para A.5.7
    Supplementary planning documentDesign of Residential Extensions SPDNo periodsutton.gov.uk
    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
    Householder: alterations/extensions to a single dwellinghouse, from 1 Apr 2026548 GBPNo periodribblevalley.gov.uk
    Conservation areas8 named conservation areas published by the councilNo periodplanning.data.gov.uk
    Listed building entries209 list entries (Historic England, within the LPA boundary)No periodplanning.data.gov.uk

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

    Sutton5 neighbouring councils
    Councils bordering Sutton

    04The streets

    Householder applications by street in Sutton

    Streets in Sutton with the most householder applications, and the share approved
    StreetApplicationsApproved
    Higher Drive3570%
    Oaks Avenue3179%
    Banstead Road South3090%
    The Gallop2893%
    Ridge Road2680%
    Foresters Drive2391%
    Pine Ridge2385%
    Pine Walk2383%
    Boundary Road2276%
    Caldbeck Avenue2273%
    Cornwall Road2282%
    Carshalton Park Road2171%
    Kingsmead Avenue2190%
    Alington Grove2095%
    Chiltern Road2090%

    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

    What that means for a mansard brief

    A conventional mansard replaces the whole slope, so at the rear it is the form the SPD names as unacceptable. The realistic route is a dormer drawn to the tests above, and we say so in the free constraints check, before you commission a survey.

    Permitted development does not rescue it. Class B requires the original eaves to be maintained or reinstated, which a parapet-fronted mansard normally removes, and Class AA additional storeys exclude houses built before 1 Jul 1948 or after 28 Oct 2018.

    Conservation areas, listed houses and the caseload

    Sutton publishes 8 conservation areas, and Historic England records 209 list entries. A listed house needs consent for the roof as well as permission: see listed building consent drawings in Sutton.

    Across 601 householder decisions the council granted 91.8%. That covers all household work, so read it as background to the borough, not as odds for a mansard.

    The drawing set

    Existing and proposed roof plans, sections and elevations, with the ridge, hip and neighbouring rooflines shown on one surveyed datum. The Party Wall etc. Act 1996 sets the timing for a party structure notice: Party structure notice at least 2 months before work.

    Fixed fee from £845 including VAT, with the council's householder fee of £548 paid separately. A basement under the same house is a different application: see basement conversion drawings in Sutton.

    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

    Rear view of brick terraced houses in London with slate roofs and chimney stacks along the shared rooflineParty wall services
    Photograph: Ben Hadfield
    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

    Can I have a mansard on the back of my Sutton house?

    Not as a mansard. The SPD says a mansard-type form on the rear slope of a conventional pitched roof will not be acceptable. A dormer within its tests is the usual alternative, with the dormer below ridge; not full slope.

    Does Sutton accept a hip-to-gable loft?

    The SPD describes hip-to-gable and half-hip changes as not encouraged, especially where they upset the symmetry of a semi-detached pair. We check your pair and the street before drawing anything.

    What do mansard roof drawings cost in Sutton?

    Our fixed fee starts at £845 including VAT, and redraws are free until approval.

    Converted loft bedroom with roof windows and a Juliet balcony

    8

    named conservation areas published by the council

    Conservation areas, Sutton. Source: planning.data.gov.uk

    Photograph: Imad Clicks

    09Further reading

    Other services in Sutton

    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 Sutton and the rear-slope rule