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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.

01Kensington and Chelsea, London

Basement conversion drawings in Kensington and Chelsea

A basement extension to a single house in Kensington and Chelsea needs planning permission, because a borough-wide Article 4 direction removed the permitted development right. The Local Plan then limits extent, depth and the garden above, and we draw to those limits from £1,995 including VAT.

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    02The brief

    Permission first: the borough-wide direction

    An Article 4 direction covering the whole Royal Borough of Kensington and Chelsea removes permitted development rights for basement extensions to single dwelling houses; it came into force on 28 April 2016. The practical effect is that the first sheet we prepare is a planning drawing, and nothing in the process starts from a permitted development check.

    The council also publishes 84 Article 4 directions in all and 39 conservation areas, so a basement under a house in a conservation area is read against the area appraisal too.

    Brick house being extended, with a wide new opening supported over the ground floor
    Georgian brick terrace with sash windows, arched fanlight doorways, stone steps and iron railings in London
    Photograph: Lorenc Memaga

    03The record

    Local figures for Kensington and Chelsea

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Basements must not exceed 50 per cent of each garden or open part of the site, with the unaffected garden kept in a single area; exceptions may be made on large sites.50%No periodrbkc.gov.uk, Local Plan 2024, Policy CD11, p.251, CD11 A
    Basements must not comprise more than one storey (exceptions on large sites) and no further basement floors may be added where a basement already has permission or was built.1 storeyNo periodrbkc.gov.uk, Local Plan 2024, Policy CD11, pp.251-252, CD11 B-C
    Basements must include a sustainable drainage system and a minimum of one metre of soil above any part of the basement beneath a garden.1 m soilNo periodrbkc.gov.uk, Local Plan 2024, Policy CD11, p.252, CD11 I-J
    Existing open areas such as lightwells count towards the garden when calculating the 50% maximum extent.50%No periodrbkc.gov.uk, Basements SPD 2016, p.10, section 3 Applicant Checklist
    Article 4 directions84 Article 4 directions published by the councilNo periodplanning.data.gov.uk
    Domestic gardens share of land (GLUD 2005)17.5 % of land that is domestic garden (GLUD 2005)2005data.london.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

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

    Kensington and Chelsea4 neighbouring councils
    Councils bordering Kensington and Chelsea

    04The drawing

    A basement in sectionA, Kensington and Chelsea: depth and garden share: 50%. B, Kensington and Chelsea: excavation depth: 1 storey. C, Kensington and Chelsea: soil over the basement: 1 m soil. D, 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. E, Escape from basement rooms: Basement storeys with habitable rooms need an escape window or external door, or a protected stair to a final exitABCDE

    A basement in section

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

    A Kensington and Chelsea: depth and garden share
    50%
    B Kensington and Chelsea: excavation depth
    1 storey
    C Kensington and Chelsea: soil over the basement
    1 m soil
    D 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
    E 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.

    05The detail

    Three numbers to design to

    The Local Plan sets three limits that a design can be built around. Extent is limited to 50% of each garden or open part of the site, and depth to 1 storey. Above any basement under a garden the plan wants 1 m soil, together with a sustainable drainage system.

    Existing lightwells and other open areas are counted into the garden when the 50% limit is worked out, so the survey measures them first. Domestic gardens make up 17.5% of the borough's land according to the Generalised Land Use Database.

    What basements did to the streets

    The conservation-area appraisals record the harm. The Chelsea Park Carlyle Conservation Area Appraisal (adopted 19 June 2017) says it directly. New basement levels have brought unsympathetic rooflights; the appraisal lists this as harm to the area. A lightwell or rooflight is therefore drawn as part of the roofline and the garden, not as a service detail.

    For the terraces between Fulham Road and the King's Road, see Chelsea's period terraces, where the area's design points are set out.

    Knightsbridge and the boundary

    Knightsbridge straddles two councils: Westminster's audit says the southern and western boundaries of its Knightsbridge conservation areas follow the boundary with the Royal Borough of Kensington and Chelsea. On the Westminster side a different policy applies. Westminster's City Plan 2019-2040 (2026), Policy 50, supports basements only where they extend under no more than 50% of the garden land and are no more than one storey beneath the lowest original floor level, with exceptions for large sites.

    Which council's rule applies depends on the side of the boundary, so we confirm the council before we draw. The Knightsbridge guide shows how the two councils meet.

    Neighbours, escape and the other applications

    Excavation beside a neighbour brings in the Party Wall etc. Act 1996. 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 notice drawings are priced from £45 per adjoining owner. Basement storeys with habitable rooms need an escape window or external door, or a protected stair to a final exit.

    The council's householder fee is £548, paid separately. A listed house needs listed building consent drawings in Kensington and Chelsea beside the planning application, and a new roof storey is covered by mansard roof drawings in Kensington and Chelsea.

    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

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

    07Correspondence

    Questions

    Does the borough-wide Article 4 direction mean a basement is not allowed?

    No. It removes the permitted development right, so you need planning permission, and the policy then sets what can be granted: extent 50% of the garden and depth 1 storey, with exceptions on large sites.

    Do existing lightwells count towards the garden limit?

    Yes. Existing open areas such as lightwells count towards the garden when the 50% limit is calculated, so the survey records them before any design work.

    How much soil must sit above a basement under a garden?

    The plan asks for 1 m soil over any part of a basement beneath a garden. That sets the slab depth early, so we fix it at the first design option.

    What do basement drawings cost here?

    The fixed fee starts at £1,995 including VAT. The council's householder fee is £548, paid to it separately, and a party wall notice is £45 per adjoining owner.

    Rows of brick terraced houses and gardens on a residential street

    17.5%

    of land that is domestic garden (GLUD 2005)

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

    Photograph: Altaf Shah

    08Further reading

    Other services in Kensington and Chelsea

    Basement conversion 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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    Basement conversion drawings in Kensington and Chelsea