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Barnet, London

L-shaped dormer drawings in Barnet

Barnet writes the L-shaped dormer into its guidance, and the figure is 50% of outrigger depth; 0.5 m. We draw L-shaped dormers for Barnet houses for a fixed quote after a free constraints check, VAT included, with the outrigger part set to that rule from the first sketch.

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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 l-shaped dormer 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.

    Request a fixed quote
    Brick cottage with a tiled roof, chimneys and a front dormer window

    What Barnet writes about L-shaped dormers

    Barnet's Sustainable Design and Development Guidance SPD, Part 4: Guidance on residential extensions and alterations says that where L-shaped dormers are a predominant local feature, the outrigger part should cover no more than half the outrigger depth. It should also be set up from the eaves on all sides and set down from the ridge, and the figures the council gives are 50% of outrigger depth; 0.5 m.

    Read it carefully. The test starts with the words "predominant local feature", so the rule helps most in a street where L-shaped dormers already exist. Elsewhere the same limits are a sensible target, but an officer is free to look for something smaller.

    We note the L-shaped dormers already visible in your street from public views and show them beside the design, so the officer can see whether the local-feature test is met. The design principles behind the guidance are in the Sustainable Design and Development Guidance SPD, Part 2: The seven features of good design.

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

    Local figures for Barnet

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Where L-shaped dormers are a predominant local feature, the outrigger part should cover no more than 50% of the outrigger depth, be set up 0.5 metres from the eaves on all sides and set down 0.5 metres from the ridge.50% of outrigger depth; 0.5 m—barnet.gov.uk, SDDG SPD Part 4 (extensions), p.25, paras 4.95-4.96
    Conservation areas16 named conservation areas published by the council—planning.data.gov.uk
    Article 4 directions15 Article 4 directions published by the council—planning.data.gov.uk
    Listed building entries651 list entries (Historic England, within the LPA boundary)—planning.data.gov.uk
    Householder decisions1,361 decisions1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder applications granted80.2 %1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder appeals decided by the Planning Inspectorate413 householder appeals decideddecision dates 1 Jul 2021 to 30 Jun 2026assets.publishing.service.gov.uk
    Householder appeals allowed50.6 % of householder appeals alloweddecision dates 1 Jul 2021 to 30 Jun 2026assets.publishing.service.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 Barnet

    Householder applications by street in Barnet

    Streets in Barnet with the most householder applications, and the share approved
    StreetApplicationsApproved
    Wolmer Gardens4282%
    Hampden Way3686%
    Oakleigh Park South3677%
    Marsh Lane3591%
    Millway3493%
    Sturgess Avenue3494%
    Uphill Road3273%
    Chanctonbury Way3190%
    Oakleigh Road North3079%
    Woodlands3076%
    Laurel Way2976%
    Mount Pleasant2880%
    Arlington Road2780%
    Berkeley Crescent27100%
    Longland Drive27100%
    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.
    Loft enlargement in section: the permitted development limitsExtra roof volume allowed: 40 m³ (terrace house) / 50 m³ (any other house) additional roof volume. Set-back from the eaves: Original eaves maintained; enlargement set at least 0.2 m from the eaves measured up the roof slope, so far as practicable (not required for hip-to-gable or roofs joining a rear/side extension). Height limit: No part higher than the highest part of the existing roofABC

    Loft enlargement in section: the permitted development limits

    A dormer on the rear slope, with the limits that decide whether it needs planning permission.

    A · Extra roof volume allowed
    40 m³ (terrace house) / 50 m³ (any other house) additional roof volume
    B · Set-back from the eaves
    Original eaves maintained; enlargement set at least 0.2 m from the eaves measured up the roof slope, so far as practicable (not required for hip-to-gable or roofs joining a rear/side extension)
    C · Height limit
    No part higher than the highest part of the existing roof

    Appeals show where the line falls

    The Planning Inspectorate decided 413 householder appeals against Barnet decisions and allowed 50.6 per cent of them. Roughly half succeeded, which means appealed refusals are often overturned, but also that an appeal is no easy second chance.

    That is the best argument for a drawing that deals with the guidance on its face. We would rather win at the council desk than at appeal.

    How Barnet decides householder applications

    The council decided 1,361 householder applications in its latest year, granted 80.2 per cent and decided 95.1 per cent in time. That is a heavy caseload handled mostly on time. A clear, complete submission keeps yours moving, because a request for more information restarts the conversation with the officer.

    Conservation areas, Article 4 and listed buildings

    Barnet has 16 conservation areas and 15 Article 4 directions, mapped as 48 areas, with 651 list entries from Historic England. The national position in a protected area is: Class B roof enlargements are not permitted development on article 2(3) land.

    About 28 per cent of the borough is Green Belt, and 718 tree preservation orders cover its gardens and streets. Neither blocks a roof, but a protected tree near the rear wall can affect scaffolding and the access for a build.

    Permitted development limits and the junction rule

    If permitted development applies, the roof you can add is limited: 40 m³ (terrace house) / 50 m³ (any other house) additional roof volume. Height too: No part higher than the highest part of the existing roof. The L-shape depends on this: Eaves-retention and 0.2 m set-back do not apply where the enlargement joins the original roof to the roof of a rear or side extension.

    The borough figures apply when an application is needed, for example inside a conservation area or where an Article 4 direction removes the rights. They are tighter than the national set-back, so a design drawn only to the national tests can fail at the council. Where the route is a planning application, we design to the borough document.

    Party walls, stairs and the cost

    Shared roofs need notices: Party structure notice at least 2 months before work. The stair allowance is: Loft conversions where 2.0 m cannot be achieved: 1.9 m at the centre of the stair, 1.8 m at the side (half width). A bigger loft needs this protection: New storey above 4.5 m by loft conversion: protect the full escape route with fire-resisting doors (min E 20) and partitions (min REI 30). We carry all three through the building regulations drawings in Barnet.

    You receive plans, the roof section, elevations and location and block plans, for a fixed quote after a free constraints check, VAT included. Another chartered technologist, not the drafter, reads each sheet cold before it goes out; should the officer want amendments, the redraw is ours to pay for, up to approval. Compare dormer loft conversion drawings in Barnet for a simpler roof. The borough overview is architectural drawings in Barnet, and Haringey and Enfield lie close by.

    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.
    Slate-clad roof extension on a yellow-brick London terraced house
    Storey by storey
    Move up and down — the car travels between floors.

    Other services in Barnet

    L-shaped dormer drawings nearby

    Questions

    How large can the outrigger part of an L-shaped dormer be in Barnet?

    The borough guidance gives 50% of outrigger depth; 0.5 m, where L-shaped dormers are a predominant local feature.

    How often are Barnet householder refusals overturned?

    The Inspectorate allowed 50.6 per cent of 413 householder appeals, so it is worth drawing to the guidance in the first place.

    Do I need to count the dormers in my street?

    The council's rule applies where L-shaped dormers are a predominant local feature, so yes, we survey the street from public views and show the result.

    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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