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The Journal

Before you build

Short, sourced guides to the rules and decisions behind extensions and lofts. We link to the official guidance so you can check the detail.

  1. Building costs and house prices in Ealing

    Ealing house prices rose 1.8% to £589,875 in August 2026 as London fell. Moving vs extending, Ealing’s 3.5m rear guide, 30 conservation areas, Article 4s and HMO rules.

  2. Building costs and house prices in Croydon

    Croydon house prices by property type from the UK HPI, published extension and loft costs, and the conservation area, Article 4 and Local Plan points to check before you build.

  3. Building costs and house prices in City of London

    City of London flat prices from the UK HPI, published refurbishment costs, and the lease, listed building, Barbican, Golden Lane and building safety rules to check before you change your flat.

  4. Building costs and house prices in Camden

    Camden house prices by property type from the UK HPI, published extension, mansard and basement costs, and the flat, conservation area, Article 4 and basement rules to check before you build.

  5. Building costs and house prices in Bromley

    Bromley house prices by property type from the UK HPI, published extension and loft costs, and the side space, Green Belt, conservation area and Article 4 rules to check before you build.

  6. Building costs and house prices in Brent

    Brent house prices by property type against the London average, published extension, loft and basement costs, and Brent’s extension guidance, conservation area and Article 4 rules to check before you build.

  7. Building costs and house prices in Bexley

    Bexley house prices by property type from the UK HPI, published extension, loft and garage conversion costs, and the conservation area and Article 4 rules to check before you build.

  8. Building costs and house prices in Barnet

    Barnet house prices by property type from the UK HPI, published extension and loft costs, and the conservation area and Hampstead Garden Suburb rules to check before you build.

  9. Do you need planning permission for a house extension?

    A plain-English walk through permitted development for extensions in England, and when you need a full application.

  10. Building costs and house prices in Barking and Dagenham

    What affects building costs in Barking and Dagenham, local house price data from official sources, and the planning points to check before you build.

  11. Loft conversions: planning, building regulations and party walls

    What permitted development allows for a loft, why building regulations always apply, and when to serve party wall notices.

  12. How to plan a budget for building work (without guessing)

    Why we don't publish price lists, and the steps that get you a reliable figure for an extension or loft.

  13. Party walls: a short guide for London homeowners

    When the Party Wall etc. Act 1996 applies to your extension or loft, and the notice periods set out in GOV.UK guidance.

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