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Hounslow, London

Side return extension drawings in Hounslow

Hounslow's Residential Extension Guidelines have a section written specifically for infill, or side return, extensions, and it sets a clear test for the eaves on the boundary. Our side return extension drawings for Hounslow homes start at £745 including VAT and are drawn to that test.

From £745 (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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    Two-storey rear extension under construction on a semi-detached house

    The infill test in Hounslow's extension guidelines

    The guidelines allow an infill extension to run the full depth of the original outrigger, the rear projection of a Victorian or Edwardian terrace. Beyond the maximum depths the guidance applies, the test becomes tighter: 2 m eaves; 45 degrees, with the roof sloping away from the neighbour. The section is headed Infill Extensions in the guidelines.

    That makes the roof section the most important drawing in a Hounslow side return. A glazed lean-to that slopes away and keeps its eaves low sits comfortably inside the test, while a flat roof with a deep parapet can fail it. We draw the section at the boundary first, then design the glazing around it.

    The borough's newer Character, Sustainability and Design Codes SPD sits alongside that guidance and sets the wider design expectations for materials and character, so we read the two together.

    House extension under construction with scaffolding, new glazed doors and building materials

    Local figures for Hounslow

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Infill (side-return) extensions may run the full depth of the original outrigger; beyond the maximum depths, eaves on the side boundary should not exceed two metres with a roof pitch no more than 45 degrees sloping away.2 m eaves; 45 degrees—hounslow.gov.uk, Residential Extension Guidelines SPD 2017, p.18-19, section 4.3 (Infill Extensions)
    Supplementary planning documentCharacter, Sustainability and Design Codes SPD2024hounslow.gov.uk
    Conservation areas33 named conservation areas published by the council—planning.data.gov.uk
    Article 4 directions3 Article 4 directions published by the council—planning.data.gov.uk
    Listed building entries519 list entries (Historic England, within the LPA boundary)—planning.data.gov.uk
    Households living in a house54 % of households living in a house or bungalow (detached, semi-detached or terraced)Census 2021nomisweb.co.uk
    Householder decisions689 decisions1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder applications granted78.5 %1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder applications decided in time97.8 % decided within 8 weeks or an agreed extended period1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Larger home extension prior approvals granted20 decisions2025 Q2 to 2026 Q1 (1 Apr 2025 to 31 Mar 2026)assets.publishing.service.gov.uk
    Larger home extension prior approvals refused59 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 Hounslow

    Householder applications by street in Hounslow

    Streets in Hounslow with the most householder applications, and the share approved
    StreetApplicationsApproved
    Firs Drive3761%
    Wood Lane3259%
    Park Drive3169%
    Parkwood Road2859%
    Worton Road2758%
    Arnold Crescent2654%
    Popes Lane2483%
    St Stephens Road2477%
    Whitton Dene2450%
    Harewood Road2378%
    Princes Avenue2382%
    Spring Grove Road2355%
    Fern Lane2268%
    Netheravon Road2273%
    North Hyde Lane2255%
    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)

    Housing mix and how Hounslow decides applications

    Only 54 per cent of Hounslow's households live in a house, and 45.7 per cent own their home, so side returns here come from a smaller stock of terraces and semis. The average terraced house sold for £611,320 in the latest figures, and the average semi-detached for £716,213.

    The council decided 689 householder applications in the latest twelve months and granted 78.5 per cent. It was prompt: 97.8 per cent were decided inside eight weeks or an agreed extension.

    Not every scheme is granted, which is one more reason to put the full boundary section on the first submission.

    Conservation areas, listing and Article 4 in Hounslow

    Hounslow has 33 conservation areas, and in them there is no permitted side extension: No side extensions under PD on article 2(3) land (conservation areas etc.). The borough also has 3 Article 4 directions, and Historic England lists 519 entries inside it, so a check of your address matters.

    Outside those, the national limit is: Side extension: single storey, max 4 m high, max half the width of the original house. Eaves near the boundary are limited too: Eaves no higher than 3 m where within 2 m of the curtilage boundary.

    Hounslow's record on larger home extension prior approvals is a warning for rear depth: 20 granted and 59 refused. A scheme that pairs a side return with a long rear is better as a full application, drawn as house extension drawings in Hounslow.

    Neighbours, heat and fees on a Hounslow side return

    The infill sits against a neighbour's wall, so notices follow. Raising a new wall on the line needs: Line-of-junction (new wall) notice at least 1 month before work. Cutting into the party wall itself calls for: Party structure notice at least 2 months before work. Our party wall notices service prepares these.

    The glass roof is limited by Approved Document L: 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. Hounslow takes the standard householder fee of £548.

    The borough levy is shown as £200/m² (CIL Zone 1, East); £110/m² (CIL Zone 2, Central); £70/m² (CIL Zone 3, West), and any liability is noted in our handover pack.

    Because the infill test turns on a boundary section, our Hounslow survey records the height of the neighbour's flank wall, the position of their eaves and the line of any gutter, so the new roof is drawn to meet them properly. Where the rear outrigger steps in, it leaves an awkward corner for the roof to turn. We resolve that corner on the drawings, including the rainwater route, because that junction is where water finds its way in if it is left to the builder.

    What the Hounslow set includes

    Plans, elevations, sections and location and block plans for £745, fixed up front, with the forms and submission if you ask. A second chartered technologist reviews the set before it goes to Hounslow, and officer-requested changes are redrawn without charge.

    For technical detail see building regulations drawings in Hounslow, and for the borough as a whole architectural drawings in Hounslow.

    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 house being extended, with a wide new opening supported over the ground floor
    Every side considered
    Flick across the turntable to spin it.

    Other services in Hounslow

    Side return extension drawings nearby

    Questions

    What is Hounslow's rule for infill extensions?

    Beyond the guideline depths, boundary eaves and roof pitch are limited: 2 m eaves; 45 degrees, with the roof sloping away from the neighbour.

    Can an infill extension run the full length of the outrigger?

    Yes, the guidelines allow the full depth of the original outrigger, subject to the other design tests.

    Does a Hounslow conservation area rule out a permitted side extension?

    Yes. Across its 33 conservation areas the national rule applies: No side extensions under PD on article 2(3) land (conservation areas etc.).

    What fee does Hounslow charge for a householder application?

    £548, the fee set nationally for householder schemes.

    Sources and dates

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    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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