Extension Options Compared
Not sure which extension type suits your home? Compare every option side by side - from rear extensions and loft conversions to full design decision comparisons. Each guide covers costs, planning requirements, and what works best for different house types in London.
Extension Types
Every type of home extension available in London, with costs, planning rules, and design considerations.
The most popular London extension. Open-plan kitchen-diners and larger living spaces.
Side Return ExtensionFill the narrow alley beside terraced houses for a wider kitchen.
Loft ConversionConvert unused roof space into bedrooms. No foundation costs.
Two-Storey ExtensionGround floor space plus an extra bedroom above. Best value per m2.
Wrap-Around ExtensionSide return plus rear extension for maximum ground floor space.
Basement ExtensionCreates significant space without reducing garden. Complex engineering.
Garage ConversionConvert an existing garage into living space. Lower cost per m2.
Kitchen ExtensionDedicated guide to kitchen extensions, layouts, and costs.
Dormer ExtensionAdd a dormer to increase loft headroom and usable floor area.
Mansard Loft ConversionThe premium loft option. Rebuilds the rear roof slope for maximum space.
Porch ExtensionFront porch additions, PD rules, and costs.
Granny AnnexeSelf-contained living space for family members. Planning rules and costs.
Garden Room vs ExtensionCompare a garden room to a traditional extension. PD, costs, and value.
Modular ExtensionFactory-built extensions. Faster construction, different cost profile.
Upward ExtensionAdd a storey on top of your existing home. New PD rules explained.
Extension Above GarageBuild above an attached or integral garage for an extra bedroom.
Head-to-Head Comparisons
Side-by-side comparisons of the most common extension decisions. Cost, value, planning, and practical differences.
The financial and practical case for extending versus selling up.
Single vs Two-StoreyCost per m2, planning requirements, and which adds more value.
Flat Roof vs Pitched RoofAesthetics, cost, planning implications, and long-term maintenance.
Orangery vs ExtensionTraditional orangery versus a standard extension. Style and cost.
Loft vs Rear ExtensionWhich gives better value? Cost, disruption, and space compared.
Bifold vs Sliding DoorsThe two most popular glazing options for rear extensions compared.
Roof Lantern vs SkylightWhich brings more light? Cost, aesthetics, and thermal performance.
Architect vs Online ServiceTraditional architect versus fixed-fee online platforms. Cost and quality.
DIY vs ProfessionalWhat you can do yourself and where you need professionals.
Extension vs New KitchenWhen a kitchen refit makes more sense than building an extension.
By House Type
Extension options and constraints specific to your property type.
Side returns, rear extensions, and loft conversions for terraces.
Semi-Detached HouseSide extensions, rear extensions, and two-storey options for semis.
Detached HouseMaximum flexibility. Wrap-arounds, two-storey, and side extensions.
FlatExtending a flat: leaseholder rights, freeholder consent, and options.
Victorian HouseSympathetic extensions for Victorian terraces and villas.
1930s SemiSide and rear extensions for the classic interwar semi-detached.
Cost & Planning Guides
Complete price guide by extension type, size, and borough.
Extension Cost by SizeHow costs scale with project size from 10m2 to 50m2+.
Hidden CostsThe costs builders do not include in their quotes.
Architect Fees London 2026What architects charge and how to compare quotes.
Permitted Development Changes 2026What has changed in PD rules and what is still proposed.
Building Regulations GuideEvery building reg for your extension in one place.