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

Basement conversion drawings in Hounslow

Hounslow publishes exact limits for a basement: a single storey, a stated reach under the garden for each house type, and lightwells measured in metres. We draw to those limits from £1,995 including VAT and coordinate the structural calculations behind them.

From £1,995 (VAT included)

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    02The brief

    The limits in Hounslow's extension guidelines

    The Residential Extension Guidelines give the basement test in one line: single storey; 3.05 / 3.65 / 4.25 m; 1 m soil. In words, a basement is a single storey and stays inside the front and side walls. Under the garden of a larger property it may reach only a set distance, which differs for terraced, semi-detached and detached houses, and a metre of soil goes back on top.

    Lightwells have their own limit: 1m front; 2m rear. The same guidance says a basement must not be a self-contained dwelling or sleeping accommodation, and that it needs a certified Construction Method Statement. Both points shape the plan before any fixture is drawn.

    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 Hounslow

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Basements should be a single storey, not extend beyond the front or side walls, and under gardens of larger properties extend no more than 3.05 metres (terraced), 3.65 metres (semi-detached) or 4.25 metres (detached), with 1 metre of soil reinstated.single storey; 3.05 / 3.65 / 4.25 m; 1 m soilNo periodhounslow.gov.uk, Residential Extension Guidelines SPD 2017, p.26, section 4.7
    Lightwells should project no more than 1m from the front wall and 2m from the rear wall; basements must not be a self-contained dwelling or sleeping accommodation, and need a certified Construction Method Statement.1m front; 2m rearNo periodhounslow.gov.uk, Residential Extension Guidelines SPD 2017, p.25-27, section 4.7
    Domestic gardens share of land (GLUD 2005)21.5 % 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
    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.

    Hounslow5 neighbouring councils
    Councils bordering Hounslow

    04The streets

    Householder applications by street in Hounslow

    Streets in Hounslow with the most householder applications, and the share approved
    StreetApplicationsApproved
    Firs Drive3761%
    Wood Lane3259%
    Park Drive3169%
    Parkwood Road2859%
    Worton Road2758%
    Arnold Crescent2654%
    Popes Lane2483%
    St Stephens Road2477%
    Whitton Dene2450%
    Harewood Road2378%
    Princes Avenue2382%
    Spring Grove Road2355%
    Fern Lane2268%
    Netheravon Road2273%
    North Hyde Lane2255%

    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, Hounslow: depth and garden share: single storey; 3.05 / 3.65 / 4.25 m; 1 m soil. B, 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. C, Escape from basement rooms: Basement storeys with habitable rooms need an escape window or external door, or a protected stair to a final exitABC

    A basement in section

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

    A Hounslow: depth and garden share
    single storey; 3.05 / 3.65 / 4.25 m; 1 m soil
    B 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
    C 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

    Gardens and the Thames policy area

    Domestic gardens cover 21.5% of the borough's land according to the Generalised Land Use Database, and garden depth is what the reach limits above are measured against. We survey the plot, the levels and the drains first, so the garden limit is checked against measured ground.

    Along the river the constraint changes. Most of the Old Chiswick Conservation Area lies within the Thames Policy Area; Chiswick Eyot is a Local Nature Reserve and Metropolitan Open Land. A house there is read against river policy as well as the basement rules, and our Chiswick guide names the conservation areas concerned.

    Digging beside a neighbour

    Excavation near a boundary 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. A dispute arises if the adjoining owner does not consent within 14 days of the notice.

    We prepare the notice drawings for each adjoining owner, priced from £45 per owner, so the notice goes out with a drawing the neighbour's surveyor can read.

    Escape, alarms and the council fee

    Building Regulations apply once the basement has habitable rooms. 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. Both are on the first issue of our drawings.

    The council's householder fee is £548, paid to it separately from our fee. A listed house needs listed building consent drawings in Hounslow beside the planning application, and a new roof storey is a separate scheme, covered by mansard roof drawings in Hounslow.

    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
    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

    How far can a basement extend under a Hounslow garden?

    It depends on the house type. The guidelines' limit reads single storey; 3.05 / 3.65 / 4.25 m; 1 m soil, with the reach set separately for terraced, semi-detached and detached houses. We read it against your plot before we draw.

    Can a Hounslow basement be a bedroom or a separate flat?

    Hounslow's guidance rules out a basement as a self-contained dwelling or as sleeping accommodation. Habitable rooms below ground also face Building Regulations. Basement storeys with habitable rooms need an escape window or external door, or a protected stair to a final exit.

    How far can a lightwell project in Hounslow?

    The guidelines' limit reads 1m front; 2m rear. Front lightwells are the ones an officer reads against the street, so we draw them against the neighbouring frontages.

    What do the drawings cost?

    The fixed fee starts at £1,995 including VAT. Council fees are separate, and the structural calculations are coordinated alongside.

    Rows of brick terraced houses and gardens on a residential street

    21.5%

    of land that is domestic garden (GLUD 2005)

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

    Photograph: Altaf Shah

    09Further reading

    Other services in Hounslow

    Basement conversion 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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    Basement conversion drawings in Hounslow