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Bright finished basement room with a glass-balustrade staircase, high windows and a built-in desk
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01Lewisham, London

Basement conversion drawings in Lewisham

Lewisham measures a basement against the house and garden as they were originally built: one storey down, and light wells held to stated distances from the original walls. Our drawings, from £1,995 including VAT, show those distances on the plan.

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    02The brief

    The SPD's limits, rear and front

    The Alterations and Extensions SPD sets a limit for the rear. In short the rear limit is one storey; 3 m or 1/4 garden: one storey below the original ground floor, with light wells no wider than the original house and reaching no further than the stated distance from the original rear wall or the stated share of the original garden, whichever is less.

    The front is stricter. Front light wells are limited on reach, width and share of the front garden, and the SPD also sets minimum headroom and soil cover over a basement under garden; each figure is in the table below. Every figure counts from the original building, so we survey what was built first, then draw the proposal against it.

    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 Lewisham

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Basements should generally be no more than one storey below the original ground floor, and including lightwells no wider than the original property nor more than 3 m from the original rear wall or a quarter of the original garden length, whichever is less.one storey; 3 m or 1/4 gardenNo periodlewisham.gov.uk, Lewisham Alterations and Extensions SPD 2019, p.44, paras 4.8.8-4.8.9
    Front lightwells: no more than 1.5 m from the front wall or half the garden length, no more than one third of the property width, no more than a quarter of the front garden area; minimum 2.4 m headroom; at least 1 m soil above a basement under garden.1.5 m; 1/3 width; 1/4 garden; 2.4 m; 1 m soilNo periodlewisham.gov.uk, Lewisham Alterations and Extensions SPD 2019, p.45-46, paras 4.8.11, 4.8.15, 4.8.20
    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
    Party Wall etc. Act 1996 s5, s6(7)A dispute arises if the adjoining owner does not consent within 14 days of the noticeNo 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
    Conservation areas30 named conservation areas published by the councilNo periodplanning.data.gov.uk
    Article 4 directions57 Article 4 directions published by the councilNo periodplanning.data.gov.uk
    Listed building entries367 list entries (Historic England, within the LPA boundary)No periodplanning.data.gov.uk
    Domestic gardens share of land (GLUD 2005)31.1 % of land that is domestic garden (GLUD 2005)2005data.london.gov.uk

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

    Lewisham4 neighbouring councils
    Councils bordering Lewisham

    04The drawing

    A basement in sectionA, Lewisham: depth and garden share: one storey; 3 m or 1/4 garden. B, Lewisham: soil over the basement: 1.5 m; 1/3 width; 1/4 garden; 2.4 m; 1 m soil. C, 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. D, Escape from basement rooms: Basement storeys with habitable rooms need an escape window or external door, or a protected stair to a final exitABCD

    A basement in section

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

    A Lewisham: depth and garden share
    one storey; 3 m or 1/4 garden
    B Lewisham: soil over the basement
    1.5 m; 1/3 width; 1/4 garden; 2.4 m; 1 m soil
    C 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
    D 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

    Garden land and soil cover

    Domestic gardens cover 31.1% of the borough's land (GLA land-use data). A basement under garden needs soil cover above it, so the roof slab and soil depth are drawn in section.

    The Local Plan is the Lewisham Local Plan 2020-2040. The council's fee for a householder application, £548, is its own charge and is not part of our quote.

    Beside the party wall, below the rear wall

    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. The original rear wall that the light well is measured from and the neighbour's foundation line both come out of the survey, so one set of dimensions serves the planning plan and the party wall notice drawings. A dispute arises if the adjoining owner does not consent within 14 days of the notice.

    The SPD's headroom and soil cover figures both use up depth, so the escape route is settled in section from the first issue. Basement storeys with habitable rooms need an escape window or external door, or a protected stair to a final exit.

    Original building, listed building

    On an older Lewisham house the original building and today's house are rarely the same footprint. A later rear extension does not move the original rear wall that the light well reach is taken from, which is why the survey records the house against its original footprint.

    The borough has 30 conservation areas, 57 Article 4 directions and 367 list entries. A listed house needs consent for digging as well as permission; see listed building consent drawings in Lewisham. The roof above is covered by mansard roof drawings in Lewisham, and the steps every borough shares by the basement conversion drawings hub.

    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

    How deep can a basement be in Lewisham?

    The council says generally no more than one storey below the original ground floor. We draw to that and to the light well limits.

    Why does the council keep referring to the original house?

    Because the limits are measured from the original rear wall, original garden length and original property width, not from later extensions. We survey and record what was originally built.

    Do I need a party wall notice?

    Often, when the excavation is close to a neighbour's foundations. We prepare party wall notices and drawings, priced per adjoining owner.

    What do I get for the fixed fee?

    From £1,995 including VAT: the surveyed drawings of the house as it stands and the proposed drawings, with the light wells dimensioned from the original building.

    Rows of brick terraced houses and gardens on a residential street

    31.1%

    of land that is domestic garden (GLUD 2005)

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

    Photograph: Altaf Shah

    08Further reading

    Other services in Lewisham

    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 Lewisham