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Merton, London

Side return extension drawings in Merton

Merton grants most householder applications but decides fewer of them within eight weeks, so a side return here is a matter of planning the timetable as carefully as the design. Our side return extension drawings for Merton start at £745 including VAT, and we build the programme around the council's real decision times.

From £745 (VAT included)

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

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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 side return extension drawings

    Nine 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.

    8. Building regulations

      Technical drawings are coordinated with the structural engineer's calculations, the drainage and the planning conditions.

    9. Approval and hand-over

      Building control approval, then a next-steps pack covering the commencement notice, party wall timing and CIL.

    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 house being extended, with a wide new opening supported over the ground floor

    What Merton's record means for a side return programme

    Over its latest twelve months Merton decided 759 householder applications, granting 92.9 per cent. Only 85.2 per cent, however, were decided within eight weeks or an agreed extension.

    That gap is the practical point. A scheme that is likely to be granted can still wait beyond eight weeks, so we advise clients not to book a builder or serve party wall notices on a hard date until the decision is in. We also complete the validation checks ourselves, because an application the council has to send back loses weeks it does not have.

    Merton has no standalone householder design guide in force, so officers rely on the local plan's extension policies. The council's published Basement and subterranean SPD concerns digging down, which matters if you plan a lower-ground floor beside the side return, and otherwise we read the local plan's extension policies against your plot.

    We can set out a decision calendar for your Merton job. It lists the validation date, the eight-week point, the likely party wall notice dates and the earliest realistic start on site. Owners who see these dates on paper make better choices about when to book a builder, and when to hold off. Where a neighbour is likely to need persuading, we suggest talking to them before the notices go out, with the drawings in hand, because a good conversation costs nothing and saves weeks.

    Finished white-rendered rear house extension with large glazed doors

    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
    Supplementary planning documentBasement and subterranean SPD2017merton.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
    Households living in a house60.4 % of households living in a house or bungalow (detached, semi-detached or terraced)Census 2021nomisweb.co.uk
    Average price, terraced686,591 GBP2026-07publicdata.landregistry.gov.uk
    Larger home extension prior approvals granted22 decisions2025 Q2 to 2026 Q1 (1 Apr 2025 to 31 Mar 2026)assets.publishing.service.gov.uk
    Larger home extension prior approvals refused80 decisions2025 Q2 to 2026 Q1 (1 Apr 2025 to 31 Mar 2026)assets.publishing.service.gov.uk
    Householder: alterations/extensions to a single dwellinghouse, from 1 Apr 2026548 GBP—ribblevalley.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

    Householder applications by street in Merton

    Streets in Merton with the most householder applications, and the share approved
    StreetApplicationsApproved
    South Park Road2696%
    Lower Morden Lane2584%
    Coombe Lane2383%
    Pepys Road2377%
    Palmerston Road21100%
    Dorset Road2072%
    Marryat Road2094%
    Mostyn Road2089%
    Springfield Avenue1995%
    Vineyard Hill Road19100%
    Claremont Avenue1888%
    Queen's Road18100%
    Faraday Road1782%
    Gladstone Road1760%
    Stroud Road1794%
    Counts of householder applications by street; no individual applications are shown. Streets with fewer than five applications are left out.Source: GLA Planning London Datahub, householder applications, all years held. Contains public sector information licensed under the Open Government Licence v3.0. Contains OS data © Crown copyright and database right 2026.
    The 45-degree test in planTest used in daylight assessments: 45 degrees (plan and elevation)A

    The 45-degree test in plan

    A line from the middle of the neighbour's nearest window: the extension should stay behind it.

    A · Test used in daylight assessments
    45 degrees (plan and elevation)

    Conservation areas and listed homes in Merton

    Merton has 28 conservation areas, and national permitted development gives no side extension in them: No side extensions under PD on article 2(3) land (conservation areas etc.). Historic England lists 243 entries in the borough, so listed building consent is a live question for some owners.

    Where no designation applies, a Merton side extension can rely on: Side extension: single storey, max 4 m high, max half the width of the original house. There is also a limit on boundary eaves: Eaves no higher than 3 m where within 2 m of the curtilage boundary.

    Where a Merton house has a side gate and a narrow passage, we record the gate position, the drain runs and any manhole in the passage during the survey, because a manhole under the new floor changes the foundation and the access cover detail.

    Housing, prior approval and cost in Merton

    60.4 per cent of Merton's households live in a house and 55.6 per cent own their home. The average terraced house sold for £686,591 and the average semi-detached for £954,064 in the latest figures.

    Prior approval for larger home extensions saw 22 granted and 80 refused, so a scheme that adds depth to the rear usually needs a full application. If a smaller scheme is plainly lawful, a lawful development certificate in Merton is the proof.

    Merton charges the householder fee of £548. The borough levy is shown as £368.20/m² (Colliers Wood, Raynes Park and Wimbledon); £192.47/m² (Mitcham, Morden and West Barnes), depending on the part of Merton.

    Neighbours and glazing on a Merton side return

    The extension sits against a neighbour's wall. Building a new wall on the line brings: Line-of-junction (new wall) notice at least 1 month before work. A cut into a shared structure needs: Party structure notice at least 2 months before work. Our party wall notices service prepares both once the design is fixed.

    For the glass roof and doors, Approved Document L sets the cap: Windows, roof windows, rooflights and doors in an extension should not exceed 25% of the extension floor area plus the area of openings removed or covered.

    What the Merton set includes

    Merton owners receive plans, elevations, sections and location and block plans for a fixed £745. Before submission a second chartered technologist checks each sheet, and amendments Merton requests are redrawn at no cost.

    If the rear is changing too, see rear extension drawings in Merton, or the overview at architectural drawings in Merton.

    If you are extending to sell, the drawings also serve as a record for the buyer's solicitor. Keep the approved set, the party wall award and the completion certificate together, and your sale pack is complete. We hand over the approved drawings in a final pack, so nothing has to be rebuilt later when a buyer asks.

    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.
    Two-storey rear extension under construction on a semi-detached house
    Every side considered
    Flick across the turntable to spin it.

    Other services in Merton

    Side return extension drawings nearby

    Questions

    Does Merton decide householder applications within eight weeks?

    Only 85.2 per cent were decided within eight weeks or an agreed extension in the latest twelve months.

    How likely is a grant?

    Merton granted 92.9 per cent of householder applications, which describes the borough and promises nothing for your house.

    Is permitted development available in a Merton conservation area?

    Not for a side extension. Across Merton's 28 conservation areas: No side extensions under PD on article 2(3) land (conservation areas etc.).

    What is Merton's householder application fee?

    £548, paid to Merton with the application.

    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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