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Hackney, London

Basement impact assessment in Hackney

Hackney has detailed basement wording: a Residential Extension and Alterations SPD chapter that limits storeys, footprint, garden take and headroom, plus a flood risk requirement in critical drainage areas. 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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    Brick cottage with a tiled roof, chimneys and a front dormer window

    Hackney's rules for a basement impact assessment

    Two documents shape a Hackney basement. The first is the borough's planning validation checklist. It asks for a Flood Risk Assessment for basement development in Critical Drainage Areas and in areas with a high risk of surface water flooding or an elevated risk of groundwater flooding in the lowest flood zone, as well as for any development in the two higher-risk flood zones. If your street sits in one of those areas, flood evidence is part of the application from day one.

    The second is chapter seven of the Residential Extension and Alterations SPD, adopted in December and in effect from January. It says a basement should be a single storey, with a headroom minimum, a footprint cap relative to the host building, a limit on how much of the garden depth and area it may take, and a minimum depth of suitable soil above any part that extends beyond the building. It also asks for sustainable drainage and careful treatment of trees and root protection areas, and it resists losing whole front gardens to lightwells. The table below carries the exact figures with their citations.

    In practice this means the design is shaped before the assessment is written. A basement that breaks the footprint or soil-cover rule is redrawn, not reported on, so we test the layout against the SPD first and then commission the ground investigation that proves the rest.

    Rear view of brick terraced houses in London with slate roofs and chimney stacks along the shared roofline

    Local figures for Hackney

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Flood Risk Assessment is required for 'major development and basement development in Critical Drainage Areas and areas with a high risk of surface water flooding or an elevated risk of groundwater flooding in flood zone 1', and for development in Flood Zones 2 and 3.Basement development in CDAs / elevated groundwater risk—docs.google.com, Hackney Planning Application Validation Checklist (Google Doc linked from hackney.gov.uk/submit-planning-application), Local Requirements table, row 'Flood Risk Assessment', item (iv)
    Residential Extension and Alterations SPD ch.7 (adopted December 2025, in effect January 2026): basements should be single storey, with minimum 2.15 m headroom, less than 1.5 times the host building footprint, no more than 50% of garden depth/area, with at least 1 m of suitable soil above any part beyond the building footprint, SuDS, and careful consideration of trees and root protection areas; loss of entire front gardens to lightwells is resisted.Single storey; <1.5x footprint; 1 m soil cover; 2.15 m headroom—drive.google.com, Hackney Residential Extension and Alterations SPD, December 2025, Chapter 7 Basements, printed p.60; ch.8 p.63
    Conservation areas37 named conservation areas published by the council—planning.data.gov.uk
    Article 4 direction areas197 Article 4 direction area polygons published by the council—planning.data.gov.uk
    Listed building entries555 list entries (Historic England, within the LPA boundary)—planning.data.gov.uk
    Domestic gardens share of land (GLUD 2005)18.5 % of land that is domestic garden (GLUD 2005)2005data.london.gov.uk
    Households living in a house18.8 % of households living in a house or bungalow (detached, semi-detached or terraced)Census 2021nomisweb.co.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 Hackney
    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

    Hackney in numbers for a dig-down project

    Only 18.8 per cent of Hackney households live in a house or bungalow, and owner-occupation is 24.6 per cent, so most basement work is in the terraced streets and in maisonette conversions that carry their own freehold or lease questions. Gardens are 18.5 per cent of the borough's land, which is why the garden-take limit bites.

    The borough names 37 conservation areas, records 77 Article 4 directions covering 197 areas and holds 555 listed entries, so heritage constraints are common. Householder applications numbered 415 in the latest year, with 84.6 per cent granted and 91.3 per cent decided in time.

    Those numbers describe the borough, not your plot. Two houses on one street can sit either side of a conservation boundary.

    Testing a Hackney layout against the SPD

    The quickest way to save money on a Hackney basement is to test the layout before the ground investigation is ordered. We measure the existing footprint, set the proposed basement beside it, and check each SPD limit in turn: storeys, headroom, footprint relative to the house, share of the garden and the soil above the part that goes beyond the building. A layout that fails any of them is redrawn on paper, which costs a few hours rather than a failed application.

    Trees come next. The SPD asks for careful treatment of root protection areas, so a mature garden tree can cap the size of the box. Where the layout clears the limits, the report is written around a design the council can actually support.

    What the assessment covers and who writes it

    The report shows the council that the house, the neighbours and the drainage will be unaffected by the new floor. A ground investigation firm and a structural engineer produce the specialist sections. We assemble the pack, draw the plans and sections it refers to and keep the figures consistent. Our structural calculations page describes 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. In a drainage-critical area that rule and the council's flood evidence should be designed together.

    Party walls, planning route and cost in Hackney

    Terraced Hackney streets mean shared walls. Under the Party Wall etc. Act 1996, excavation within 3 metres of a neighbour and below their foundations needs 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 wider figures are on architectural drawings in Hackney. Islington and Tower Hamlets border Hackney but set their own basement rules.

    This is unpriced because scope depends on site and flood status. 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.
    Pencil resting on a dimensioned technical drawing beside a scale rule
    The street around you
    Move across the plinth — the blocks rise around the pointer.

    Other services in Hackney

    Basement impact assessments nearby

    Questions

    What does Hackney's SPD say about basements?

    It sets out limits on storeys, headroom, footprint, garden take and soil cover, and asks for drainage and tree care. The figures are in the table on this page with their citation.

    Does a Hackney basement need a flood risk assessment?

    In Critical Drainage Areas and in areas with high surface water or elevated groundwater risk in the lowest flood zone, yes. We check which applies to your address.

    Can I extend a Hackney front garden for a lightwell?

    The SPD resists the loss of entire front gardens to lightwells, so a small, well-screened one is more likely to succeed than a full-width one.

    Is a flat or maisonette basement possible?

    Often only with the freeholder's consent and a clear title. We check the lease position before any design work.

    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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