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Merton, London

Retrospective planning applications in Merton

If a loft, extension or outbuilding in Merton went up without permission, you can ask the council to approve it after the event. It judges the building as though it were still a proposal. Last year it decided 759 householder applications and granted 92.9 per cent. We survey what stands, draw it as built and prepare the application. 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 retrospective planning applications

    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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    Pencil resting on a dimensioned technical drawing beside a scale rule

    How Merton's policies meet a retrospective application

    Merton's policies come from the Merton Local Plan 2024, adopted in 2,024, and its supplementary guidance: the Borough Character Study SPD, the Small sites toolkit SPD and the Basement and subterranean SPD. The council publishes no separate rule for regularising finished work, so the case officer applies the same design tests to your building that they would apply to a drawing.

    For most houses that means three questions. Does the extension respect the rhythm of the street described in the Borough Character Study? Does it leave neighbours with acceptable light and privacy? Does it keep a usable garden? A rear dormer that overshadowed nobody and matches its neighbours has a better case than one that wraps the whole roof.

    A house with a basement is judged against the basement guidance as well, so tell us at the first call if you dug down.

    Rows of brick terraced houses and gardens on a residential street

    Local figures for Merton

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Householder decisions759 decisions1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder applications granted92.9 %1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder applications decided in time85.2 % decided within 8 weeks or an agreed extended period1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Lawful development certificate applications (PS1)58 certificates2025 Q2 to 2026 Q1 (1 Apr 2025 to 31 Mar 2026)assets.publishing.service.gov.uk
    Conservation areas28 named conservation areas published by the council—planning.data.gov.uk
    Listed building entries243 list entries (Historic England, within the LPA boundary)—planning.data.gov.uk
    Local planMerton Local Plan 2024—merton.gov.uk
    Supplementary planning documentBorough Character Study SPD2021merton.gov.uk
    Average price, terraced686,591 GBP2026-07publicdata.landregistry.gov.uk
    TCPA 1990 s171B(1)-(3) as substituted by LURA 2023 s115, in force 25 Apr 202410 years—legislation.gov.uk
    Householder: alterations/extensions to a single dwellinghouse, from 1 Apr 2026548 GBP—ribblevalley.gov.uk
    DMPO 2015 art 37(2)(a): householder appeal, from the date of the decision notice12 weeks—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 Merton
    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 the council's figures tell a homeowner

    The council decided 759 householder applications in its latest published year and granted 92.9 per cent, with 85.2 per cent decided within 8 weeks or an agreed extension. These figures describe all householder cases, not only retrospective ones, so read them as a sign of how Merton treats domestic extensions in general.

    A strong grant rate is no promise for your address. Officers still walk round the site, and an unauthorised extension that fails a design test is refused like any other. Our job is to find out before we submit whether the work can stand, needs a modest amendment or should come down in part.

    Merton's terraced houses averaged £686,591 in the latest Land Registry month and semi-detached houses £954,064. At those values, an unresolved planning breach can hold up a sale far more than the cost of putting it right.

    Check whether you need a retrospective application at all

    Some work that looks unauthorised is lawful. If the building has stood for long enough, or was built within permitted development, a certificate proves it and no planning application is needed. In its latest published year Merton handled 58 certificate applications for existing development, so the route is well used.

    Our Lawful Development Certificate drawings in Merton cover that case. Where the work breaches a limit and is too recent to be immune, we prepare the retrospective application with the planning drawings the council expects.

    The time limit for enforcement against most unauthorised building works is 10 years, but waiting is rarely wise. Evidence of when something was built fades quickly.

    Constraints that can sink an as-built extension

    Merton has 28 conservation areas, 243 listed building entries and 23 Heritage at Risk entries. If your house sits in a conservation area, a dormer or front change built under a mistaken belief in permitted development is much harder to defend. A listed house needs listed building consent, which is a different application altogether.

    Merton also has an Article 4 direction removing the right to convert a family house to a small HMO without permission. If part of your as-built work created extra bedrooms, say so early, because it changes the policies the officer reads.

    Our measured building survey records the true dimensions, so the drawings match what the officer sees on site.

    Fees, timing and the appeal route

    The council's fee for a householder application is £548, paid to Merton on submission. It has 8 weeks to decide unless you agree longer. If it refuses, you have 12 weeks to lodge a householder appeal, and our planning appeals service can take that on.

    Our own price is fixed once we have checked your constraints. If the officer asks for changes, we redraw free of charge. Browse every service we offer in the borough on our architectural drawings in Merton page.

    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 Merton

    Retrospective planning applications nearby

    Questions

    Can Merton refuse a retrospective application for a loft that is already built?

    Yes. The council applies the same policies as for a new proposal, and being built is not a reason to approve. Our survey and drawings show whether your loft meets the Borough Character Study SPD and neighbouring amenity tests before we submit.

    How many certificate of lawfulness applications does Merton handle?

    The council's return shows 58 certificate applications for existing development in its latest published year. A certificate can remove the need for a planning application when the work is old enough or was permitted development.

    Is the application fee for retrospective work higher?

    For a householder case the fee is £548, the same table as any extension. We confirm the exact sum from the live fee table in your quote.

    What if I built a basement in Merton without permission?

    The council's Basement and subterranean SPD sets the tests for subterranean work. We check structure, drainage and neighbouring land first, because basements are the most difficult unauthorised works to regularise.

    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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