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Westminster, London

Biodiversity net gain plans in Westminster

Westminster has very little garden land, and that changes what a biodiversity net gain plan means here. Gardens cover just 7.9 per cent of the land, so the habitat on a typical site is a few trees, a roof or a courtyard. Almost every home project is exempt. New buildings are not, and the national gain of 10 per cent applies. We quote a fixed price 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 biodiversity net gain plans

    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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    Rows of brick terraced houses and gardens on a residential street

    How net gain works in a borough with almost no gardens

    We found no Westminster rule with a published value that goes beyond the statutory figure, so the national metric and the national gain apply. The council's framework is the City Plan 2019-2040 (2026), which the borough adopted in 2,026.

    The metric was written with fields and hedgerows in mind, and in the middle of London it measures something different. A site's baseline might be a single plane tree, a strip of paving with a planter and a flat roof. Those score very little, so the gain required in absolute terms can be small, but it still has to be shown, drawn and maintained.

    The practical answer is almost always on the building: a biodiverse green roof, planted terraces, living walls where the structure allows, and trees in the public realm where the council will accept them. Those features go on the drawings as well as in the spreadsheet.

    Because the figures are small, the weak point is rarely the arithmetic. It is evidence. An officer in central London will want to see that the roof can carry the planting, that someone will maintain it for the full period, and that the species suit the exposure. We therefore attach a short maintenance and management note to the plan, written so that a managing agent or freeholder can follow it without specialist help.

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

    Local figures for Westminster

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Domestic gardens share of land (GLUD 2005)7.9 % of land that is domestic garden (GLUD 2005)2005data.london.gov.uk
    Tree preservation orders685 tree preservation orders published by the council—planning.data.gov.uk
    Tree preservation zones263 tree preservation zone polygons published by the council—planning.data.gov.uk
    Conservation areas56 named conservation areas published by the council—planning.data.gov.uk
    Listed building entries4,015 list entries (Historic England, within the LPA boundary)—planning.data.gov.uk
    Households living in a house10.2 % of households living in a house or bungalow (detached, semi-detached or terraced)Census 2021nomisweb.co.uk
    Householder applications granted82 %1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Environment Act 2021 Sch 14 para 2, inserting Sch 7A TCPA 1990: 'relevant percentage' 10%10 %—legislation.gov.uk
    'Developments of 0.2 hectares or below': from 6 August 2026 BNG does not apply where the site area within the red line boundary is 0.2 ha or below0.2 ha—gov.uk
    Sch 7A para 9(3) as inserted: enhancement maintained for at least 30 years after completion30 years—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 Westminster
    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

    Trees carry the baseline

    Westminster publishes 685 tree preservation orders and 263 protection zones, and it has 56 conservation areas where trees are protected anyway. On a small central site one large tree can be most of the baseline value.

    That makes the arboricultural survey the most important document in the plan. If a tree can be retained, the habitat is kept and the gain is easier. If it cannot, the replacement planting needs space that a central site rarely has, and the shortfall may have to be met off site.

    Ask us before any tree work. A large specimen, once removed, is hard to replace with anything the metric will value as highly.

    Listed buildings and conservation areas shape the options

    Historic England lists 4,015 entries in Westminster, and the borough contains 1 world heritage site. On a listed building a green roof may not be acceptable, and a living wall may be refused on the facade. The planting that is allowed is therefore settled before the metric is run.

    The council's guidance on Roofs: a guide to alterations and extensions on domestic buildings SPG and Mews: a guide to alterations SPG also limits what can sit on a roof or in a mews. We design the greening against those documents first, so the plan does not propose a feature that conservation officers will not accept.

    Our new build drawings and planning drawings pages explain how the building and landscape sheets are prepared together.

    Who needs a plan in Westminster

    Householder applications are exempt, as is development granted by a development order. In practice a flat refurbishment or a rear addition needs no plan, though the form must say so. Only 10.2 per cent of households live in a house, so many owners here apply as flats and the householder exemption does not always apply to them.

    Sites of 0.2 hectares or below are exempt, and since central sites are nearly all small, the small-site exemption does most of the work. A larger redevelopment can still be caught.

    In the latest returns the council granted 82 per cent of householder applications and decided 79 per cent in time.

    Price and next step

    A plan has no list price. You receive a fixed quote after a free constraints check, which tells you whether an exemption applies before you spend anything on surveys.

    Our biodiversity net gain page explains the national rules, and the Westminster area page lists the other services we offer in the borough.

    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 Westminster

    Biodiversity net gain plans nearby

    Questions

    Does a Westminster flat conversion need a plan?

    Usually not if the site is below the small-site threshold of 0.2 hectares, but the form must say why.

    Can a green roof deliver the gain?

    Often, yes. Where the building is not listed, a biodiverse roof can supply much of a central site's gain.

    Do trees matter on a small central site?

    Very much. With 685 tree preservation orders published, a single protected tree can be most of the baseline.

    How long is the gain kept?

    At least 30 years after completion.

    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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