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Bromley, London

Basement impact assessment in Bromley

For a basement in Bromley the first question is often the site's status, ahead of the soil: 51 per cent of the borough is covered by green-belt polygons, and it publishes 108 Article 4 directions. We coordinate the basement impact assessment on a fixed quote after a free constraints check.

Fixed quote after a free constraints check

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  • £2m PI insured
  • LABC Partnered
  • Fixed fees, VAT included

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    Architectural model of a four-storey London stucco townhouse in its terrace, with a portico, area railings, sash windows, a cornice and chimney stacks
    The house as it stands: four storeys over a lower ground floor.Existing Proposed worksAn illustrative model, built for this page.

    How we work on basement impact assessments

    Seven steps from first call to approval.

    The same model cut through the middle: every floor, the stair, the chimney breasts, the new mansard, rear extension and basement in section
    Section through the model: every floor on one datum.

    1. Enquiry and constraints check

      We check the property against conservation areas, listed status, Article 4 directions, tree preservation orders, flood zone and planning history. We choose the right route and send a fixed quote.

    2. Measured survey

      We survey the house on one datum: rooms, levels, boundaries, drains, trees and the neighbours' windows that the 45° and 25° tests depend on.

    3. Design options

      We model the house in Revit and show you options in 3D and plan, with the planning strategy and the precedents in your street.

    4. Design frozen

      You choose an option in writing. Nothing changes after this without your say.

    5. Independent check

      A second chartered technologist checks every sheet against the council's validation checklist and the policy. A senior review signs it off before anything is submitted.

    6. Submission

      We prepare the forms, certificates, fee and documents and submit through the Planning Portal.

    7. Officer liaison

      We answer the planning officer and make any amendments within five working days, at no charge until approval.

    Free redraws until approval. Every drawing set is checked independently, and the checker is never the person who drew it.

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

    How Bromley's rules frame a basement impact assessment

    The development plan is the Bromley Local Plan, adopted in 2,019, and the council's own design reference is the Urban Design Guide SPD. We have not found a stand-alone basement document with figures we can quote, so this page does not invent one. The method is to read the plan's policies on flooding, trees and residential extensions against your address, then say in writing what the council is likely to ask for.

    That reading often changes the project. Where a house sits in the green belt, any enlargement is judged against the openness of the land, and a basement that adds a rooflight, a lightwell or a raised terrace can alter the answer. A fully buried basement under the footprint of the house is a different proposition from one that extends into the garden.

    So we ask three things before the free check ends: where the house sits against the green-belt edge, whether an Article 4 direction touches the street, and how deep and how far the dig would go.

    Brick cottage with a tiled roof, chimneys and a front dormer window

    Local figures for Bromley

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Green Belt share of the council area51 % of council area covered by green-belt polygons—planning.data.gov.uk
    Article 4 directions108 Article 4 directions published by the council—planning.data.gov.uk
    Conservation areas47 named conservation areas published by the council—planning.data.gov.uk
    Listed building entries412 list entries (Historic England, within the LPA boundary)—planning.data.gov.uk
    Householder applications granted78.6 %1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder appeals allowed37.6 % of householder appeals alloweddecision dates 1 Jul 2021 to 30 Jun 2026assets.publishing.service.gov.uk
    Domestic gardens share of land (GLUD 2005)23.4 % of land that is domestic garden (GLUD 2005)2005data.london.gov.uk
    Local planBromley Local Plan—bromley.gov.uk
    Borough CIL residential rate£120.12/m² (Residential development excluding residential development which delivers additional care and support services)rate for planning permissions granted in 2026 (permission year index 400, schedule base index 333)bromley.gov.uk
    Party Wall etc. Act 1996 s6(1): excavation within 3 m horizontally of an adjoining owner's building or structure and deeper than the bottom of its foundations3 m—legislation.gov.uk

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

    Councils bordering Bromley
    Which application your project needsLawful Development Certificate decision: 8 weeks. Prior approval decision: 42 days. Householder decision: 8 weeksYour projectWithin permitted development?Lawful Development CertificatePrior approvalHouseholder applicationYesLarger rear extensionNoABC

    Which application your project needs

    The usual route for a house; flats and listed buildings follow other rules.

    A · Lawful Development Certificate decision
    8 weeks
    B · Prior approval decision
    42 days
    C · Householder decision
    8 weeks

    Article 4 directions, heritage and the ground in Bromley

    The borough has 108 Article 4 directions, 47 conservation areas and 412 listed entries, of which 380 are Grade II. The effect on a basement is practical: a direction can remove the permitted development rights for the front of a house, so a lightwell facing the road needs permission.

    Historic England also records 25 entries on the Heritage at Risk Register in the borough. A house next to one of them draws a closer look at the street scene, so we photograph the frontage early and describe the materials of any visible lightwell, grille or railing on the elevation.

    Because the dig goes under the house, the engineer also needs to know how the existing walls are built and how deep their footings are. We measure the house, record the levels along the boundary and pass the engineer a dimensioned set, so the ground investigation is aimed at the right place and the design starts from facts.

    Domestic gardens cover 23.4 per cent of the land, and 68.6 per cent of households live in a house. Generous plots mean there is room for a basement, but also more trees, more levels and more neighbours' boundaries to survey.

    What Bromley's decisions and appeals say

    Bromley decided 1,609 householder applications in its latest year and granted 78.6 per cent, with 89.1 per cent decided in time. The Planning Inspectorate decided 502 householder appeals against the borough and allowed 37.6 per cent.

    Those figures tell us that applications here are tested hard, and that an appeal is a real route but not an easy one. They do not isolate basements, so we treat them as context, not prediction.

    Our approach is to resolve the council's likely objections in the drawings and the report before you apply. A scheme that is clear on depth, drainage and trees has less to explain to an officer.

    Cost, levy and neighbours

    Bromley's Community Infrastructure Levy for residential development is £120.12/m² (Residential development excluding residential development which delivers additional care and support services), and the national rules have no basement-specific exemption, so new floorspace can be liable. We list it in the next-steps pack so there is no surprise after the permission.

    Next door, a dig within 3 metres of an adjoining building that goes deeper than its foundations needs a party wall notice, as does one within 6 metres on the diagonal test. Serve it at least 1 month before work.

    Building Regulations require drainage or protection where the water table can rise within 0.25 metres of the lowest floor, whatever the planning outcome.

    Price and where to look next

    A basement impact assessment is an unpriced service. After the free check you get a fixed quote, with our planning drawings in Bromley covering the application that carries the report.

    The borough overview is architectural drawings in Bromley. Closer to the centre of London, Westminster sets numeric limits on garden and depth, a useful contrast, and the national rules are on the basement impact assessment hub.

    What you receive

    Planning drawing sheet for a rear extension with plans, elevations and sections
    Sample drawing. Planning drawings for a rear extension: plans, elevations and sections on one sheet set.
    Rear view of brick terraced houses in London with slate roofs and chimney stacks along the shared roofline
    The street around you
    Move across the plinth — the blocks rise around the pointer.

    Other services in Bromley

    Basement impact assessments nearby

    Questions

    Does Bromley need a basement impact assessment?

    It depends on the scheme and the address. We read the local plan against your site and say in writing whether a report is likely before you pay for one.

    Does the green belt stop a basement in Bromley?

    Not by itself, but enlargements in the green belt are judged on openness, so the above-ground parts of a basement matter. We check the site status first.

    How many Article 4 directions does Bromley have?

    108, which is why we check your road against the list before we draw a lightwell.

    How much does the work cost?

    A fixed quote after a free constraints check, because depth, soil and site status change the scope.

    Sources and dates

    City of London skyline glowing at dusk across the Thames under a dramatic orange sky

    Tell us about your property.

    We check the constraints, then send a fixed fee. Messages before 3pm get a reply the same working day.

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