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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.

01City of London, London

Basement conversion drawings in the City: few houses, much beneath them

Houses are rare in the Square Mile, with 2% of households living in one, and gardens make up 0.1% of the land in an older London survey. A basement here almost always means going down under an existing building. We draw the structure as it stands and the proposed lower floor from £1,995 including VAT, with the party wall and escape requirements shown on the sheets.

From £1,995 (VAT included)

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    02The brief

    No basement policy has reached our records

    No City rule on basement depth, garden share or storeys has come into our records, so this page quotes none. The London Plan gives the direction: Boroughs should set policies on large-scale basements where this is a local issue. The City of London Local Plan 2015 is the document we search at the start of each job.

    Rear view of brick terraced houses in London with slate roofs and chimney stacks along the shared roofline
    Brick house being extended, with a wide new opening supported over the ground floor
    Photograph: Brett Jordan

    03The record

    Local figures for City of London

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Domestic gardens share of land (GLUD 2005)0.1 % of land that is domestic garden (GLUD 2005)2005data.london.gov.uk
    Households living in a house2 % of households living in a house or bungalow (detached, semi-detached or terraced)Census 2021nomisweb.co.uk
    Households4,914Census 2021 (21 March 2021)nomisweb.co.uk
    Householder decisions1 decisions1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Conservation areas28 named conservation areas published by the councilNo periodplanning.data.gov.uk
    Listed building entries637 list entries (Historic England, within the LPA boundary)No periodplanning.data.gov.uk
    Grade I listed entries86 list entriesNo periodplanning.data.gov.uk
    Scheduled monuments53 scheduled monuments intersecting the LPA boundary (Historic England)No periodplanning.data.gov.uk
    Registered parks and gardens5 registered parks and gardens intersecting the LPA boundary (Historic England)No periodplanning.data.gov.uk
    Listed building consent decisions (PS2)154 listed building consent decisions (to alter or extend)2025 Q2 to 2026 Q1 (1 Apr 2025 to 31 Mar 2026)assets.publishing.service.gov.uk
    Listed building consents granted (PS2)99.4 % granted2025 Q2 to 2026 Q1 (1 Apr 2025 to 31 Mar 2026)assets.publishing.service.gov.uk
    Local planCity of London Local Plan 2015No periodcityoflondon.gov.uk
    Supplementary planning documentBarbican Estate Listed Building Management Guidelines: Volume I Introduction and Volume II Residential (SPD)2012cityoflondon.gov.uk
    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
    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
    Approved Document B Vol 1, paras 1.1-1.2All dwellings: fire detection and alarm system minimum Grade D2 Category LD3 (BS 5839-6), mains-operated smoke alarms to BS EN 14604No 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.

    City of London7 neighbouring councils
    Councils bordering City of London

    04The 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.

    05The detail

    What the ground and the building already hold

    Historic England records 637 list entries within the boundary, 86 of them at Grade I, and the council publishes 28 conservation areas. Digging beneath a listed building changes its structure and its foundations, so listed building consent drawings in the City of London is usually the first application to settle.

    The same register holds 53 scheduled monuments and 5 registered parks and gardens in the boundary. We plot any designation near your address before design starts, because protected remains are a reason to change a design early and not late.

    The Barbican and its guidelines

    Residential work on the listed Barbican estate follows the council's Barbican Estate Listed Building Management Guidelines: Volume I Introduction and Volume II Residential (SPD). We read that document for any scheme there, and the consent route above applies to the estate as it does to any other listed address.

    Households in the borough number 4,914, so a house with its own basement is a rarity, and the council's householder statistics for its latest year list 1 decided. Each job is therefore judged on its own facts.

    Next door, exits and detection

    A City building seldom stands alone, so the Party Wall etc. Act 1996 reaches almost every dig: 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. A dispute arises if the adjoining owner does not consent within 14 days of the notice.

    Escape from below ground follows Building Regulations: Basement storeys with habitable rooms need an escape window or external door, or a protected stair to a final exit. The fire detection standard for the dwelling reads: All dwellings: fire detection and alarm system minimum Grade D2 Category LD3 (BS 5839-6), mains-operated smoke alarms to BS EN 14604. To see how a borough with firm figures compares, read basement conversion drawings in Westminster or the basement conversion hub. A roof change on the same building is described in mansard roof drawings in the City of London.

    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

    Georgian brick terrace with sash windows, arched fanlight doorways, stone steps and iron railings in LondonListed building consent
    Photograph: Lorenc Memaga
    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

    What protected remains might lie under a City property?

    The borough contains 53 scheduled monuments, and the list covers many more buildings. We check which designations are near your address before design begins and tell you what they mean for the dig.

    How does the City treat listed building consent applications?

    In its latest year the council decided 154 applications to alter or extend a listed building and granted 99.4% of them. A basement under a listed building is the sort of work that needs one.

    Is the London Plan enough to guide a City basement design?

    It sets the expectation that boroughs act where basements are a local issue: Boroughs should set policies on large-scale basements where this is a local issue. We have not found a City limit, so we confirm the council's position when we survey.

    What do drawings for a City basement cost?

    Our fee starts at £1,995 including VAT, and the council's own householder fee of £548 goes to the council. Party wall notices are priced per adjoining owner.

    Rows of brick terraced houses and gardens on a residential street

    0.1%

    of land that is domestic garden (GLUD 2005)

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

    Photograph: Altaf Shah

    08Further reading

    Other services in City of London

    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 the City of London