Two-Storey Rear Extension: Planning Permission Rules
Two-storey rear extensions always need planning permission — they are not permitted development. How the application works, the 45-degree rule, and design considerations.

Practical guidance on Permitted Development and householder projects in England — what the rules allow, what they limit, and what it means for your drawings.
Start with the PD guideOur detailed guidance pages, organised by the kind of project you are planning.
Permitted Development rulesThe limits that apply to each type of householder project.View articles
ExtensionsSingle storey rear, side and two storey rear extensions.View articles
Lofts and roofsLoft conversions, dormers and roof alterations.View articles
Garden buildingsOutbuildings, garden rooms and garages.View articles
Around the housePorches, conservatories, windows and doors.View articles
Boundaries and outsideFences, walls, gates, patios and driveways.View articles From our Permitted Development and planning article library.
Two-storey rear extensions always need planning permission — they are not permitted development. How the application works, the 45-degree rule, and design considerations.
Part 20 permits one or two additional storeys on houses and commercial buildings with Prior Approval. How Class AA, Class A, and the commercial classes work.
Semi-detached houses can build single-storey side extensions under permitted development. Find out the size limits, loft conversion rules, and party wall obligations.
Most conservatories don’t need planning permission. Learn the size limits and when Building Regulations apply to conservatories.
Can you build a two-storey rear extension without planning permission? Learn the 3m limit, 7m boundary rule, and when side extensions always need PP.
Can you build a side extension without planning permission? Our guide covers permitted development rules for single storey side extensions — width limits, height rules, and conservation area restrictions.
PERMITTED HOMEOWNER GUIDES
Our illustrated, practical guides help you understand the rules, explore design options and budget with confidence — before you commit to building work.
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Rules, design options, costs and next steps.
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Rules, design options, costs and next steps.
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Rules, design options, costs and next steps.
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Rules, design options, costs and next steps.
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Rules, design options, costs and next steps.
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Rules, design options, costs and next steps.
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Rules, design options, costs and next steps.
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Rules, design options, costs and next steps.
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