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Bright finished basement room with a glass-balustrade staircase, high windows and a built-in desk
Photograph: Point3D Commercial Imaging Ltd.

01Sutton, London

Basement conversion drawings for Sutton houses

Sutton is a borough of family houses: 62.9% of households live in a house or bungalow, and domestic gardens cover 34.5% of the land. A basement here sits under a house with a garden still above it, so the drawings have to show the soil, the water and the neighbour as clearly as the new rooms. We draw them from £1,995 including VAT, after a free constraints check.

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    02The brief

    A semi, a detached house and the wall they share

    The two house types people ask us about most in Sutton sit a long way apart on price. Land Registry figures put the average semi-detached sale at £657,577 and the average detached sale at £1,038,684, a gap that shapes what extra floor area is worth to each owner.

    They also differ underground. A semi shares a foundation line with its pair, so the Party Wall etc. Act is almost certainly in play. A detached house has no party wall, but the Act still looks at distance: 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. We measure to the neighbour's footings before saying which side of that line you fall.

    Georgian brick terrace with sash windows, arched fanlight doorways, stone steps and iron railings in London
    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 Sutton

    Figures with their unit, period and source
    MeasureValuePeriodSource
    London Plan 2021 Policy D10(A)Boroughs should set policies on large-scale basements where this is a local issueNo periodlondon.gov.uk
    Party Wall etc. Act 1996 s6(1), s6(2), s6(5)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 foundationsNo periodlegislation.gov.uk
    Approved Document B Vol 1, para 2.16Basement storeys with habitable rooms need an escape window or external door, or a protected stair to a final exitNo periodgov.uk
    Householder: alterations/extensions to a single dwellinghouse, from 1 Apr 2026548 GBPNo periodribblevalley.gov.uk
    Domestic gardens share of land (GLUD 2005)34.5 % of land that is domestic garden (GLUD 2005)2005data.london.gov.uk
    Households living in a house62.9 % of households living in a house or bungalow (detached, semi-detached or terraced)Census 2021nomisweb.co.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 Basement Impact Assessment is a listed supporting document for major, minor and householder applications proposing basements; the assessment should include investigations into groundwater levels and the impact on groundwater flows.Groundwater levels and flow investigationNo periodsutton.gov.uk, London Borough of Sutton Local Validation List (adopted 24 August 2026), p.25 (content); p.11, 15, 19, 37 (matrix)

    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 basement in sectionA, Party wall notice for excavation: 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. B, Escape from basement rooms: Basement storeys with habitable rooms need an escape window or external door, or a protected stair to a final exitAB

    A basement in section

    A house and garden over a single-storey basement. The lettered marks show the limits the legend gives.

    A Party wall notice for excavation
    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
    B Escape from basement rooms
    Basement storeys with habitable rooms need an escape window or external door, or a protected stair to a final exit
    The basement in three dimensions3D
    Scroll the page: the model turns with it.

    06The detail

    What the council wants investigated first

    The Sutton Local Plan 2016-2031 comes with a validation list, and that list names a basement impact assessment for householder, minor and major applications alike. The part it stresses is Groundwater levels and flow investigation. A ground investigation therefore often sets the programme, so we raise it before drawing the lower floor.

    The wider frame is London-wide and loose: Boroughs should set policies on large-scale basements where this is a local issue. We treat the assessment, not a depth limit, as Sutton's real test, and our section drawings are drawn to feed it.

    Keeping the garden a garden

    Where the box runs past the back wall, the soil above it has to be deep enough to plant and drain properly. We put the build-up, the falls and the outlet on the sheet. The reviewer then sees the garden as it will be in ten years, and the cellar as it will be on day one.

    The family-house pattern matters for lightwells too. A front lightwell on a street of matching semis is read against its neighbours, and the council's Design of Residential Extensions SPD is its own yardstick for extensions of that kind.

    Levies, exits and alarms

    Extra floor area can attract the Community Infrastructure Levy, but a basement often does not. No CIL where new build gross internal area is under 100 m², unless one or more dwellings are created. Sutton also charges its own levy, shown in the council schedule as £100/m² (Residential, borough-wide), and the Mayor's levy here sits in band 3.

    A habitable lower floor must also be safe to leave and quick to warn. Basement storeys with habitable rooms need an escape window or external door, or a protected stair to a final exit. All dwellings: fire detection and alarm system minimum Grade D2 Category LD3 (BS 5839-6), mains-operated smoke alarms to BS EN 14604.

    Listed streets, conservation areas and the roof

    The borough has 8 conservation areas and Historic England records 209 list entries. If your house is one of them, the cellar needs its own consent, and listed building consent drawings in Sutton sets out how we prepare it.

    Owners who dig down often look up next. The council resists a mansard form on a rear slope, and mansard roof drawings in Sutton explains what it is likely to accept instead.

    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

    Brick house being extended, with a wide new opening supported over the ground floorStructural calculations
    Photograph: Brett Jordan
    Structural calculation sheet for a steel beam over a new rear opening, with the load diagram, loading table and section checks
    Sample drawing. Beam B1 over a new rear opening: loading, bending moment and section checks.

    08Correspondence

    Questions

    Will a Sutton semi need a basement impact assessment?

    Expect to, because the council's validation list asks for one with any application that includes a basement. It looks at groundwater levels and flow, so a site investigation usually comes before the drawings are finished.

    How much of my garden can a Sutton basement take?

    We have no council percentage on record, so the limit is the one you set: leave enough depth of soil, a working drain and the trees you want to keep. We draw that build-up on the section so the officer can judge it.

    My house is detached, so do I still need to tell the neighbours?

    Possibly. The Act turns on how close and how deep you dig compared with their foundations, not on whether a wall is shared. We check the distances on your survey, and prepare the notice drawings if the test is met.

    What do I pay the council for a Sutton basement application?

    For a householder application the council's fee is £548. Our fixed price starts at £1,995 including VAT. A larger scheme can fall under a different application type and fee.

    Can a basement go under a listed house in Sutton?

    It alters the fabric, so listed building consent is needed as well as planning permission. We draw both from one survey, with the existing structure recorded first.

    Rows of brick terraced houses and gardens on a residential street

    34.5%

    of land that is domestic garden (GLUD 2005)

    Domestic gardens share of land (GLUD 2005), Sutton, 2005. Source: data.london.gov.uk

    Photograph: Altaf Shah

    09Further reading

    Other services in Sutton

    Basement conversion drawings nearby

    10Sources

    Sources and dates

    Licences

    • 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.
    • GLA Planning London Datahub, householder applications. Contains public sector information licensed under the Open Government Licence v3.0.
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    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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    Basement conversion drawings in Sutton