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Havering, London

Basement impact assessment in Havering

Havering asks for a basement impact assessment wherever a basement is new or extended, citing the London Plan basement policy, and says the detail should match the scale, location and complexity of the scheme. It can sit inside the Flood Risk Assessment or a structural survey. We are chartered architectural technologists and give a fixed quote after a free constraints check.

Fixed quote after a free constraints check

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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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    Havering's rule for a basement impact assessment

    The council's householder application checklist states that a basement impact assessment is required where there is a new or extended basement, referring to the London Plan's basement policy. The wording matters for two reasons. First, there is no size threshold: a small cellar conversion and a full-footprint dig both trigger it. Second, the checklist says the level of detail should be commensurate with scale, location and complexity, so the report you need for a modest basement under a bungalow is not the report a deep dig in a flood-prone street would need.

    The checklist also allows the assessment to form part of the Flood Risk Assessment or a Structural Survey rather than stand alone. That flexibility saves money where the site is simple, and it is why we scope the report to your plot rather than quoting one fixed bundle. We found no Havering basement document with depth or garden percentage limits, so the officer judges the substance case by case.

    Our practice is to confirm the council's current checklist before design starts, since it is undated, and then decide whether a combined flood and structural statement is enough or a full independent report is safer.

    Rows of brick terraced houses and gardens on a residential street

    Local figures for Havering

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Basement Impact Assessment required where there is a new or extended basement (London Plan D10); detail commensurate with scale, location and complexity, and it can form part of the Flood Risk Assessment or Structural Survey.Any new or extended basement—havering.gov.uk, Havering Planning Application Checklist, Householder Applications (undated), pdf p.9, row 'Basement Impact Assessment'
    Households living in a house76.7 % of households living in a house or bungalow (detached, semi-detached or terraced)Census 2021nomisweb.co.uk
    Green Belt share of the council area53 % of council area covered by green-belt polygons—planning.data.gov.uk
    Conservation areas11 named conservation areas published by the council—planning.data.gov.uk
    Listed building entries146 list entries (Historic England, within the LPA boundary)—planning.data.gov.uk
    Householder applications granted85.9 %1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder applications decided in time97.8 % decided within 8 weeks or an agreed extended period1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Approved Document C (2004 ed. incl. 2010/2013) para 3.2: where the water table can rise to within 0.25 m of the lowest floor, drain by gravity or other effective means; para 3.4 groundwater stability; basement walls under groundwater pressure covered in the walls section0.25 m—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 Havering
    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

    Havering's housing and constraints in numbers

    Havering is dominated by houses: 76.7 per cent of households live in a house or bungalow and 69.5 per cent own their home. Green Belt covers 53 per cent of the borough, and the council names 11 conservation areas and 146 listed entries.

    Householder work is the council's bread and butter. It decided 985 householder applications in the latest year, granted 85.9 per cent and decided 97.8 per cent in time, with 96.4 per cent of minor applications in time. A request for more information on a basement stops the clock.

    Domestic gardens are 19.5 per cent of the land. Bungalows and chalet houses on generous plots are good candidates for a basement, and Green Belt locations need the surrounding works tested as well.

    Proportion is the point in Havering

    The council's own wording asks for detail in proportion to scale, location and complexity, so the best Havering submissions are neither padded nor bare. For a basement beneath a bungalow on a quiet street, a combined flood and structural statement may carry the case. For a deep dig close to a neighbour or a watercourse, it should not. Deeper excavation beside an older house, or a plot close to a river or stream on the flood maps, calls for borehole readings, a monitoring plan for the neighbouring walls and a standalone report that the case officer can read without cross-referencing three other documents.

    We therefore scope each project from the site. The free constraints check looks at depth, adjoining buildings and flood mapping, and the quote says which level of report we recommend and why. That prevents you paying for a heavyweight report the officer does not need, or sending a light one that stalls validation.

    What the assessment shows and who writes it

    It shows the structure, groundwater and surface water will be unharmed. A ground investigation firm drills and reports, a structural engineer designs the box, and we draw the plans and sections, coordinate every document and keep the levels consistent. Our structural calculations page explains the engineer's role.

    Approved Document C asks for a drained floor where the water table can rise to within 0.25 metres of it.

    Party walls, planning route and cost in Havering

    Under the Party Wall etc. Act 1996, excavation within 3 metres of an adjoining building and below its foundations needs a notice, as does a dig within 6 metres on the 45-degree test. Our party wall notices service prepares the plans.

    Planning drawings come from our planning drawings work, and the borough's figures are on architectural drawings in Havering. Redbridge and Barking and Dagenham border Havering and set their own rules.

    The service is unpriced. After the free constraints check you receive a fixed quote.

    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.
    Georgian brick terrace with sash windows, arched fanlight doorways, stone steps and iron railings in London
    The street around you
    Move across the plinth — the blocks rise around the pointer.

    Other services in Havering

    Basement impact assessments nearby

    Questions

    Does a small Havering basement need an assessment?

    The checklist asks for one wherever a basement is new or extended, though the detail should match the scale and complexity of the scheme.

    Can the assessment be part of another report?

    Yes. Havering's checklist says it can form part of the Flood Risk Assessment or a Structural Survey.

    Does Green Belt block a basement?

    Not by itself, but Green Belt covers 53 per cent of the borough, so the works around the basement are tested too.

    Sources and dates

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    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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