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Browse real extensions, calculate costs and design your own extension, all in one place

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Top extensions for you

Ground floor rear

£86k · Oct '23

Ground floor rear

£85k · Apr '24

Ground floor rear

£112k · Sep '24

Ground floor rear

£69k · Dec '21

Ground floor rear

£72k · Jan '24

Loft main dormer and ground floor rear

£156k · Dec '23

Ground floor rear

£56k · Apr '23

Ground floor rear and garden annex

£92k · Oct '21

Loft main dormer

£66k · Feb '22

Loft main dormer and ground floor rear

£213k · Sep '24

Ground floor rear

£74k · Mar '22

Ground floor rear

£113k · May '24

Ground floor rear

£45k · Aug '24

Ground floor rear and internal alterations

£96k · Dec '23

Ground floor rear and internal alterations

£106k · Nov '22

Ground floor rear and internal alterations

£145k · Jul '24

Loft L shaped dormer

£146k · Feb '24

Loft L shaped dormer and ground floor wraparound

£232k · Apr '23

Guides for your project

A single storey side extension with glass ceiling.

Costs And Financing

How much does a single storey extension cost in 2026?

Published Jan '22 • Last updated Nov '26 • 12 min read →

A side return or infill extension, featuring a glazed ceiling and sliding doors.

Costs And Financing

How much does a side return extension cost?

Published Feb '18 • Last updated Feb '26 • 7 min read →

A large kitchen diner with natural light coming from skylights and sliding glass doors.

Kitchen extensions: the ultimate guide for UK homeowners

Published Dec '21 • Last updated Oct '25 • 9 min read →

A woman uses her new country-style kitchen, made possible through permitted development rights and a rear extension.

Planning Permission

Do you need planning permission for a single storey extension?

Published Jan '22 • Last updated Oct '25 • 6 min read →

This rear extension project was financed under a remortgage and built in London.

Planning Permission

Can I add a rear extension under permitted development in the UK?

Published Aug '22 • Last updated Oct '25 • 8 min read →

Building an extension to your neighbours- boundary

Planning Permission

How close can you build your extension to your neighbours' boundary?

Published Jun '23 • Last updated Oct '25 • 3 min read →

A conservatory kitchen extension exterior shot, taken in London from a house extension project from 2019.

Planning Permission

House extension without planning permission: what are the rules?

Published Feb '22 • Last updated Oct '25 • 10 min read →

The grey flooring outside the home moves into the rich, warm material of the kitchen.

Costs And Financing

The cost of a rear extension in the UK and how to save some pennies

Published Aug '22 • Last updated Oct '25 • 8 min read →

A shovel goes into the soil of a property, ready to assess the foundations for a single storey extension.

Construction And Builders

What is the ideal depth of foundations for my single storey extension?

Published Jan '22 • Last updated Oct '25 • 5 min read →

Most loved projects

Ground floor rear

£73k · Jul '22

Ground floor side and rear

£98k · Oct '24

Ground floor rear

£96k · Feb '24

Ground floor rear

£113k · May '24

Ground floor rear

£112k · Sep '24

Ground floor rear

£90k · Feb '22

Ground floor rear

£108k · Mar '24

Ground floor rear

£85k · Apr '24

Ground floor side infill

£110k · Sep '24

Ground floor rear

£101k · May '24

Ground floor rear

£45k · Aug '24

Ground floor rear

£74k · Mar '22

Ground floor rear

£45k · May '24

Internal alterations and two storey rear

£243k · Sep '24

Ground floor side

£63k · May '24

Ground floor side infill

£164k · Jun '24

Ground floor side infill

£84k · Jun '23

Ground floor rear

£51k · Jul '22

Configure your own design

Browse examples, calculate costs and design your own extension with Resi Research Hub Get started

Budget friendly ideas

Loft hip to gable with main dormer

£75k · May '24

Ground floor rear

£63k · Jan '25

Loft main dormer and two storey side

£75k · Mar '24

Ground floor rear

£79k · May '23

Ground floor side infill

£64k · Aug '24

Ground floor side infill and ground floor wraparound

£70k · Mar '23

Loft main dormer and garage conversion

£56k · Jan '25

Ground floor side infill

£54k · Aug '23

Loft L shaped dormer

£74k · Nov '23

Internal alterations, internal alterations & first floor rear over outrigger

£76k · May '22

Ground floor side infill

£41k · Apr '24

Garage conversion

£61k · Aug '23

Loft main dormer

£60k · Jan '24

Ground floor side infill

£66k · Apr '24

Ground floor rear

£70k · Mar '24

Ground floor rear

£69k · Dec '21

Ground floor rear

£73k · Jul '24

Ground floor rear and internal alterations

£73k · Sep '22

Popular articles

Image: Small bronze and white bathroom. Article: Building regulations for downstairs WC

Design Process

Downstairs toilet building regulations: size, ventilation and drainage

Published Jul '19 • Last updated Nov '26 • 6 min read →

Starting a side-return extension project

All you need to know before starting your side return extension project

Published Feb '23 • Last updated Oct '25 • 6 min read →

A white brick side extension, tucked onto a London terraced property.

Extension Types

Single storey side extensions: everything you need to know

Published Jan '22 • Last updated Oct '25 • 5 min read →

A conservatory kitchen extension exterior shot, taken in London from a house extension project from 2019.

Extension Types

7 things to consider when building a kitchen conservatory extension

Published Jan '22 • Last updated Oct '25 • 8 min read →

A single storey flat roof extension in Barnet, with a pale brick exterior.

Extension Types

5 single storey extension ideas for your home (on a budget)

Published Dec '21 • Last updated Oct '25 • 5 min read →

Permitted development rights: A guide

Planning Permission

What are permitted development rights? A 2025 guide

Published Aug '20 • Last updated Oct '25 • 10 min read →

The drawings of a floor plan for a residential extension.

Planning Permission

What is a lawful development certificate, and when do you need one?

Published May '19 • Last updated Oct '25 • 8 min read →

A man has a set of architectural floorplans on his lap.

Planning Permission

Top 10 reasons planning permission is refused

Published Apr '18 • Last updated Oct '25 • 4 min read →

Am I in a conservation area?

Planning Permission

Am I in a Conservation Area?

Published Apr '23 • Last updated Oct '25 • 3 min read →

Ground floor side and garage conversion

£362k · Jun '24

Internal alterations, ground floor wraparound & first floor side

£336k · Feb '26

Internal alterations, airspace new floor & facade alterations

£453k · Jan '24

Ground floor side infill and Loft L shaped dormer

£321k · Aug '26

Loft hip to gable with main dormer, garage conversion, garden annex & ground floor side and rear

£376k · Jan '25

Ground floor rear, ground floor front, two storey side & internal alterations

£338k · Sep '24

Garden annex, ground floor wraparound & internal alterations

£312k · Nov '24

Loft main dormer and two storey wraparound

£367k · May '23

Loft main dormer, ground floor rear, garage conversion, garden annex, first floor rear & first floor side

£335k · Sep '24

Loft main dormer, ground floor rear, internal alterations & two storey front

£386k · Sep '25

Internal alterations, Loft L shaped dormer, ground floor wraparound, internal alterations & facade alterations

£359k · Jan '24

Loft main dormer and ground floor rear

£301k · Sep '25

Loft main dormer, ground floor rear & two storey side

£310k · May '24

Ground floor rear

£365k · Jul '24

Garden annex, Loft L shaped dormer & ground floor wraparound

£347k · Oct '22

Loft hip to gable with main dormer, internal alterations, ground floor wraparound, first floor rear & first floor side

£364k · Sep '25

Airspace new floor

£422k · Feb '24

Ground floor side infill and first floor rear over ground floor

£348k · Sep '24

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