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Hounslow, London

Flat conversion drawings in Hounslow

Hounslow splits its charging zones east to west and reads a conversion against a Local Plan written in 2,015, so the same house can cost and score differently depending on its postcode. We prepare flat conversion drawings in Hounslow from £1,195 including VAT, as MCIAT chartered architectural technologists, with the zone and the design codes checked before the layout is fixed.

From £1,195 (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 flat conversion drawings

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

    The Hounslow documents a conversion is read against

    Three documents decide most conversions here. The development plan is the Hounslow Local Plan 2015-2030 (Volumes 1 and 2). The design guidance is the Character, Sustainability and Design Codes SPD. And the money is set by the London Borough of Hounslow CIL Charging Schedule, which charges different rates in an eastern, a central and a western zone.

    Unlike some boroughs, Hounslow does not print a single floor-area threshold for conversions that we can quote as a figure, so we do not invent one. Instead the case officer reads the scheme against the plan's housing and design policies, the national space standard and the London Plan. Our job is to answer each of those in the drawings, so that the officer finds the evidence without writing back to ask for it.

    In practice that means a space schedule for each flat, a statement of how the entrance, bins and cycle store are arranged, and a plan of the garden showing who has which part. Our flat conversion drawings guide describes the full set, and we tailor it to what this borough reads for.

    Upper floors of a large yellow-brick Victorian house in London with chimney pots

    Local figures for Hounslow

    Figures with their unit, period and source
    MeasureValuePeriodSource
    Minor application decisions312 decisions1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Minor applications granted72.4 %1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Minor applications decided in time97.1 % decided within 8 weeks or an agreed extended period1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Householder applications granted78.5 %1 July 2025 - 30 June 2026assets.publishing.service.gov.uk
    Households living in a house54 % of households living in a house or bungalow (detached, semi-detached or terraced)Census 2021nomisweb.co.uk
    Listed building entries519 list entries (Historic England, within the LPA boundary)—planning.data.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
    Mayoral CIL charging band2 MCIL2 charging band (1-3)—london.gov.uk
    Mayoral CIL rate (indexed)72.73 £/m² (indexed, permissions granted in 2026)—london.gov.uk
    Borough CIL residential rate£200/m² (CIL Zone 1, East); £110/m² (CIL Zone 2, Central); £70/m² (CIL Zone 3, West)schedule rate (2015); the council states the 2026 index figure is 400 but publishes no indexed rates on its CIL pagepfm.exacom.co.uk
    Change of use of a building to one or more separate dwellinghouses, not more than 10: per dwellinghouse, from 1 Apr 2026610 GBP per dwelling—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
    Building regulations, layer by layerPart A: structure: Approved Document A: Structure, 2004 edition incorporating 2004, 2010 and 2013 amendments. Part B: fire safety: All dwellings: fire detection and alarm system minimum Grade D2 Category LD3 (BS 5839-6), mains-operated smoke alarms to BS EN 14604. Part L: insulation: New elements in existing dwellings, limiting U-values W/(m²·K): roof 0.15, wall 0.18, floor 0.18, windows 1.4 (or WER Band B), doors 1.4. Part K: stairs: 2.0 m clear headroom over stairs. Full plans application: Building control body must decide a full plans application within 5 weeks, or longer if agreed in writingPart A: structurePart B: fire safetyPart L: insulationPart K: stairsFull plans applicationABCDE

    Building regulations, layer by layer

    The Approved Documents that shape most house projects, from structure to the application itself.

    A · Part A: structure
    Approved Document A: Structure, 2004 edition incorporating 2004, 2010 and 2013 amendments
    B · Part B: fire safety
    All dwellings: fire detection and alarm system minimum Grade D2 Category LD3 (BS 5839-6), mains-operated smoke alarms to BS EN 14604
    C · Part L: insulation
    New elements in existing dwellings, limiting U-values W/(m²·K): roof 0.15, wall 0.18, floor 0.18, windows 1.4 (or WER Band B), doors 1.4
    D · Part K: stairs
    2.0 m clear headroom over stairs
    E · Full plans application
    Building control body must decide a full plans application within 5 weeks, or longer if agreed in writing

    Decision speed and grant rate for minor schemes

    Turning a house into two or three flats is a minor application. Over the latest twelve months Hounslow decided 312 of them and granted 72.4 per cent. Of those, 97.1 per cent were decided inside eight weeks or an agreed extension.

    The householder figure is different: 689 decisions with 78.5 per cent granted. A conversion is judged more critically than a rear extension, so a clean set of drawings counts for more than it would on a simple householder job.

    A quick council clock is useful, but it also leaves little room to repair a thin first submission. We aim to answer the standard questions in the first set, because a fast authority tends to decide on what it is given.

    A borough of flats, a heritage site and an Article 4 list

    Only 54 per cent of Hounslow households live in a house or bungalow, and 45.7 per cent own their home. That mix means many streets already contain flats, which matters when an officer weighs a further conversion against neighbours' amenity.

    The borough holds 519 listed building entries, 33 conservation areas and 1 World Heritage Site, with 3 Article 4 directions removing permitted development rights in named places. If your house is listed or in a conservation area, the front door, window and bin-store changes a conversion needs may be subject to closer control.

    We check the address against each designation during the survey stage. See our Hounslow area page for the full list of local constraints.

    Costs: levies, fees and the sale price gap

    The Mayor charges for new floor area, and Hounslow sits in band 2, with an indexed rate of £72.73 per square metre for permissions granted this year. The borough's own levy is zoned, and the exact rates by zone are shown in the table. The usual small-scheme exemption does not apply where a new dwelling is created.

    The council's planning fee is £610 for each flat. As a sense of the market, a terraced house in the borough averages about £611,320 and a flat about £352,823.

    We flag levy exposure and fee in the next-steps note, so you can set the budget before you instruct a builder. Where the scheme is approved, the building regulations drawings are the technical stage that follows.

    What we produce and what to read next

    Each Hounslow set has existing and proposed floor plans, elevations, sections, a block plan and the schedule of areas. If you plan to sell or let the flats separately, each will need lease plans.

    Across the boundary, flat conversion drawings in Hillingdon show how a neighbouring borough sets a stricter test.

    What you receive

    Building regulations section drawing showing the construction build-up
    Sample drawing. Building regulations section showing construction build-up for a building control check.
    Red-brick mansion blocks and shopfronts on a street corner
    Unit by unit
    Move up and down — the nearest units slide out.

    Other services in Hounslow

    Flat conversion drawings nearby

    Questions

    Does Hounslow have a minimum house size for flat conversions?

    We have not found a published figure we can quote, so we read the Local Plan and design guidance and test the layout against the national and London standards.

    Why does the borough's levy depend on where my house is?

    The council's charging schedule splits the borough into an eastern, a central and a western zone, each with its own rate per square metre.

    Is a conversion in Hounslow a minor application?

    Two or three flats count as minor development, which the council decides in a shorter period than major schemes.

    Can I convert a listed house into flats?

    A change of use may need listed building consent as well as planning permission. We check the listing before quoting.

    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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