020 7864 7245Request a fixed quote

Brent, London

Basement impact assessment in Brent

Brent says outright when a report is needed: a basement impact assessment is required for every householder application that includes a basement. The borough also sets hard limits on size and depth in its Basement SPD. We coordinate the report on a fixed quote after a free constraints check.

Fixed quote after a free constraints check

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

Request a fixed quote

We use it to check conservation areas and constraints.
Pick the council that decides your application.
A few lines: what you want to build, and anything the council has already said.
Add photos or drawings

Drop files here or choose from your device

PDF, JPG, PNG, DWG · up to 10 files, 90 MB in total

    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.

    Request a fixed quote
    Rows of brick terraced houses and gardens on a residential street

    Brent's basement impact assessment rules, point by point

    Brent's validation list for householder applications leaves no room for doubt: a report is required for every application that includes a basement, summarised in the rules table below as all basement householder applications. There is no screening threshold to argue about, so the question is how to do the report well. The design limits sit in the Basement Supplementary Planning Document, under the Brent Local Plan 2019-2041.

    The scale limits come next. In summary, a basement should not be wider than the original house, should not run far beyond the rear wall and should be one storey deep. The borough's figures, in short: 1 storey; 3 m from rear; 4 m detached / 3 m other. Larger basements are accepted only in exceptional circumstances, so we draw to these limits unless the site gives a strong reason not to.

    Garden and front-of-house rules follow, in short: 3 m; 800 mm lightwell; 50% front soft landscaping. Those numbers decide how a lightwell looks from the pavement, and how much of the front garden must stay green.

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

    Local figures for Brent

    Figures with their unit, period and source
    MeasureValuePeriodSource
    A Basement Impact Assessment is required for all householder applications that include a basement.all basement householder applications—brent.gov.uk, Brent validation list: Householder Planning Permission, p.1, 'Basement impact assessment'
    Scale limits: a basement should not be wider than the original house, extend more than 3 m from the rear of the property, or involve more than one storey of excavation (4 m floor-to-ceiling for a detached house, 3 m in other cases). Larger basements only in exceptional circumstances.1 storey; 3 m from rear; 4 m detached / 3 m other—brent.gov.uk, Brent Basement SPD (adopted June 2017), p.9, 'Scale'; p.12 (3 m into garden)
    Garden and lightwell limits: basement extends no further than 3 m from the rear into the garden; rooflights close to the building; front lightwells project no more than 800 mm or half the front garden length (whichever is less); where lightwells are proposed, re-landscape at least 50% of the remaining front garden as soft landscaping.3 m; 800 mm lightwell; 50% front soft landscaping—brent.gov.uk, Brent Basement SPD (adopted June 2017), p.9 (External Elements); p.12 (2.5 Trees & Gardens)
    A self-contained basement dwelling is classed highly vulnerable and not acceptable in flood zones 3a or 3b; development in flood zones 2 and 3 and areas of localised flooding needs a Flood Risk Assessment and Drainage Strategy by a suitably qualified specialist; all basements should have flood resilience measures including a pumped device against sewer flooding.FRA + drainage strategy FZ2/3—brent.gov.uk, Brent Basement SPD (adopted June 2017), p.13, 2.6 Flood Risk and Drainage; p.15 resilience
    Conservation areas23 named conservation areas published by the council—planning.data.gov.uk
    Article 4 directions39 Article 4 directions published by the council—planning.data.gov.uk
    Listed building entries93 list entries (Historic England, within the LPA boundary)—planning.data.gov.uk
    Householder applications granted86.6 %1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Supplementary planning documentBasement Supplementary Planning Document2017brent.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 Brent
    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

    What goes into a Brent report, and the flood test

    For full applications, the council lists what the assessment must contain: a site survey with photographs, a tree report, a landscaping assessment where the garden is affected, a heritage statement, an archaeological survey in priority areas, flood and drainage evidence, a land contamination assessment and a noise assessment for any external plant. That is a long list, and several items come from specialists, so the order we commission them matters.

    Flood risk has its own line, set out in the data table below. A self-contained basement flat is the sharpest case, because it is not acceptable in the two worst flood zones at all.

    Our role is to combine the contributions into one consistent submission. A tree report that disagrees with the section, or a drainage strategy that ignores the lightwell, invites a request for further information. We check the cross-references before anything is sent.

    We also sequence the specialists. The site survey and photographs come first, because the tree report, the landscaping check and the drainage strategy all depend on them. The structural engineer follows once the limits are fixed on the plan, so the design is not redone when the council reads the garden figures.

    Brent's constraints and decision record

    Brent has 23 conservation areas, 39 Article 4 directions across 162 mapped areas, and 93 listed entries. A basement beneath a listed house or inside a conservation area needs the heritage statement the council lists, written into the same pack.

    The borough decided 879 householder applications in its latest year, granting 86.6 per cent, with 97.2 per cent decided in time.

    Only 43.3 per cent of Brent households live in a house, so many basement enquiries come from owners of the houses that remain, where gardens cover 30.3 per cent of the borough's land. A tight plot makes the half-garden and lightwell rules bite sooner, which is why we measure the garden before we promise a layout.

    Party wall and Building Regulations alongside Brent's rules

    A Brent basement is also controlled by the Party Wall etc. Act. Excavation within 3 metres of an adjoining building that goes deeper than its foundations needs a notice, and so does a dig within 6 metres on the diagonal test. The neighbour has 14 days to respond in writing.

    Building Regulations set the floor drainage test where the water table can rise to within 0.25 metres of the lowest floor. Our structural calculations page explains how the engineer's design fits with the sheets we draw.

    Cost and where to go next

    There is no list price, because the scope depends on depth, ground and flood zone. After the free check we send a fixed quote, and we say so plainly if your scheme falls outside the borough's limits.

    The wider borough picture is under architectural drawings in Brent, and the planning application that carries the report is our planning drawings in Brent service. For a contrasting policy, Camden's five-stage process shows a screening-led approach, 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.
    Brick cottage with a tiled roof, chimneys and a front dormer window
    The street around you
    Move across the plinth — the blocks rise around the pointer.

    Other services in Brent

    Basement impact assessments nearby

    Questions

    Does a householder basement in Brent need an assessment?

    Yes. The council requires a basement impact assessment for every householder application that includes a basement.

    How deep and how far back can a Brent basement go?

    The Basement SPD limits it to one storey and a short distance from the rear wall, and it should not be wider than the original house. Larger basements are accepted only in exceptional circumstances.

    Can I have a basement flat in Brent?

    A self-contained basement dwelling is classed highly vulnerable and is not acceptable in the two worst flood zones. Elsewhere it needs flood resilience measures, including a pumped device.

    What does it cost?

    A fixed quote after a free constraints check, because the report's contents depend on the site.

    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.

    Request a fixed quoteCall 020 7864 7245WhatsApp