Login Instant quote

Research Hub

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

Design Fee Calculator

→

Build Cost Calculator

→

Timeline Calculator

→

Value-Add Calculator

→

PD Quiz

→

Top extensions for you

Ground floor rear

£83k · Oct '23

Ground floor rear

£78k · Apr '24

Ground floor rear

£103k · Sep '24

Ground floor rear

£69k · Jan '24

Ground floor rear

£66k · Dec '21

Loft main dormer and ground floor rear

£150k · Dec '23

Ground floor rear

£54k · Apr '23

Ground floor rear and garden annex

£89k · Oct '21

Loft main dormer

£64k · Feb '22

Loft main dormer and ground floor rear

£205k · Sep '24

Ground floor rear

£72k · Mar '22

Ground floor rear

£108k · May '24

Ground floor rear

£43k · Aug '24

Ground floor rear and internal alterations

£89k · Dec '23

Ground floor rear and internal alterations

£102k · Nov '22

Ground floor rear and internal alterations

£140k · Jul '24

Loft L shaped dormer

£141k · Feb '24

Loft L shaped dormer and ground floor wraparound

£223k · Apr '23

Ground floor side infill and internal alterations

£54k · Sep '22

Loft L shaped dormer and ground floor wraparound

£191k · Mar '23

Loft main dormer

£72k · Jan '22

Internal alterations

£40k · May '24

Ground floor rear and two storey side

£244k · Jan '23

Internal alterations, internal alterations & first floor rear over outrigger

£73k · May '22

Garage conversion

£61k · Jun '23

Loft main dormer and ground floor rear

£164k · Oct '22

Internal alterations and garage conversion

£61k · Sep '22

Loft outrigger dormer and internal alterations

£129k · Jan '23

Ground floor rear

£70k · Jul '22

Ground floor side infill and internal alterations

£78k · Jun '24

Loft main dormer

£61k · Jun '23

Ground floor side infill and Loft L shaped dormer

£167k · Jul '23

Ground floor rear and internal alterations

£122k · Apr '22

Ground floor rear

£43k · Mar '23

Loft main dormer

£101k · Aug '24

Loft L shaped dormer and loft roof terrace

£95k · Feb '23

Ground floor rear, internal alterations & internal alterations

£116k · Jan '23

Ground floor rear and internal alterations

£66k · Oct '23

Ground floor rear and internal alterations

£93k · Jun '22

Loft L shaped dormer and ground floor wraparound

£154k · Oct '23

Loft main dormer, ground floor rear & internal alterations

£231k · Jul '24

Internal alterations

£57k · Oct '24

Ground floor side infill

£102k · Sep '24

Ground floor side infill

£91k · Jun '22

Ground floor side infill

£79k · Feb '23

Ground floor rear and ground floor side infill

£77k · Feb '23

Ground floor wraparound and internal alterations

£107k · Sep '22

Ground floor rear

£61k · Jan '25

Guides for your project

Permitted Development

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

09 Jul '25 • 8 min read →

Single Storey Extension

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

09 Jul '25 • 5 min read →

Single Storey Extension

Do you need planning permission for a single storey extension?

09 Jul '25 • 6 min read →

House Extensions

House extension without planning permission: what are the rules?

09 Jul '25 • 10 min read →

House Extensions

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

09 Jul '25 • 3 min read →

Side Return Extensions

How much does a side return extension cost?

22 Apr '25 • 7 min read →

Rear Extensions

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

10 Apr '25 • 8 min read →

Single Storey Extension

Single storey extension costs: what you need to know

12 Jul '24 • 6 min read →

Kitchen Extensions

Kitchen extensions: the ultimate guide for UK homeowners

12 Jul '24 • 9 min read →

Most loved projects

Ground floor rear

£70k · Jul '22

Ground floor rear

£103k · Sep '24

Ground floor rear

£72k · Mar '22

Ground floor rear

£108k · May '24

Ground floor side and rear

£94k · Oct '24

Ground floor side infill

£102k · Sep '24

Ground floor rear

£92k · Feb '24

Two storey rear

£128k · Sep '24

Ground floor rear

£78k · Apr '24

Ground floor rear

£90k · Aug '24

Two storey rear

£155k · Jan '24

Ground floor rear

£100k · Mar '24

Loft main dormer

£61k · Jun '23

Internal alterations and two storey rear

£234k · Sep '24

Ground floor rear

£71k · Mar '24

Configure your own design

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

Budget friendly ideas

Ground floor side infill

£37k · Nov '22

Internal alterations

£69k · Jun '22

Internal alterations

£42k · Mar '24

Ground floor rear

£74k · Sep '22

Ground floor side infill

£77k · Sep '23

Internal alterations, internal alterations & garage new build

£71k · Dec '21

Ground floor rear

£72k · Jan '23

Ground floor rear

£57k · Jan '25

Ground floor rear

£74k · Feb '22

Ground floor rear

£43k · Mar '23

Ground floor rear

£79k · Jan '23

Loft hip to gable with main dormer

£69k · May '24

Ground floor side infill

£79k · Mar '23

Loft hip to gable with main dormer

£75k · Mar '24

Loft L shaped dormer and ground floor wraparound

£76k · Mar '24

Ground floor rear

£66k · Jan '24

Ground floor side infill and internal alterations

£44k · Jun '24

Ground floor rear and internal alterations

£67k · Sep '23

Ground floor side infill

£66k · Nov '23

Ground floor side infill

£71k · Sep '24

Internal alterations

£57k · Oct '24

Ground floor rear

£72k · Mar '24

Ground floor side

£64k · Dec '24

Ground floor side infill

£61k · Jan '23

Ground floor side infill and internal alterations

£73k · Jan '23

Ground floor rear

£45k · Jan '24

Ground floor side infill

£42k · Jun '23

Loft main dormer

£57k · Sep '24

Loft L shaped dormer

£73k · Dec '23

Ground floor rear

£71k · Jun '24

Internal alterations and ground floor wraparound

£77k · Apr '23

Ground floor side and garage conversion

£66k · Sep '22

Ground floor side infill and internal alterations

£39k · May '22

Ground floor rear

£78k · Mar '23

Loft L shaped dormer and first floor rear

£72k · Feb '24

Ground floor side infill

£69k · Oct '24

Internal alterations

£52k · Jan '24

Ground floor rear

£44k · Jan '24

Loft hip to gable with main dormer

£68k · Mar '22

Garage conversion

£59k · Aug '23

Ground floor side

£61k · May '24

Internal alterations

£77k · Jul '22

Ground floor side infill and Loft L shaped dormer

£68k · Feb '25

Loft outrigger dormer

£51k · Feb '24

Ground floor wraparound and internal alterations

£52k · Jul '23

Loft outrigger dormer

£52k · Oct '22

Ground floor side infill

£70k · Nov '22

Ground floor rear

£65k · Jul '24

Ground floor rear

£69k · Jan '24

Ground floor rear

£64k · Jun '24

Ground floor side infill

£78k · Jan '22

Loft main dormer

£56k · Jul '24

Ground floor rear

£53k · Oct '23

Internal alterations

£77k · Mar '23

Ground floor rear

£59k · Apr '24

Ground floor side infill

£63k · Apr '24

Internal alterations, Loft L shaped dormer & first floor balcony

£75k · Nov '23

Loft roof terrace

£22k · Aug '24

Ground floor rear

£65k · Jan '24

Ground floor side infill

£40k · Apr '24

Ground floor rear

£69k · May '23

Loft main dormer

£64k · Apr '23

First floor rear

£61k · Sep '22

Loft main dormer

£55k · Jan '24

Ground floor rear

£61k · Jan '25

Ground floor side infill

£50k · Aug '23

Internal alterations

£54k · Oct '24

Ground floor rear

£64k · Sep '24

Internal alterations and first floor rear over ground floor

£64k · Aug '24

Ground floor rear

£66k · Sep '23

Ground floor rear

£76k · May '23

Ground floor side infill and internal alterations

£54k · Sep '22

Ground floor rear

£65k · Jul '23

Internal alterations

£67k · Jan '22

Ground floor side infill

£79k · Feb '23

Ground floor rear

£44k · Aug '24

Ground floor rear

£75k · Jul '22

Ground floor side infill

£46k · Oct '24

Ground floor side infill

£62k · Jun '23

Ground floor side infill and internal alterations

£76k · Aug '23

Ground floor rear

£68k · Jul '24

Ground floor rear

£61k · May '24

Ground floor rear

£70k · Jul '22

Ground floor rear

£43k · Aug '24

Ground floor side infill

£70k · Oct '23

Ground floor rear

£59k · Jun '24

Ground floor rear

£77k · Jun '23

Ground floor rear

£67k · Sep '23

Garage conversion and internal alterations

£51k · Dec '23

Ground floor rear

£72k · Mar '22

Ground floor side infill

£45k · Nov '23

Ground floor rear

£70k · Dec '23

Garage conversion

£35k · Sep '23

Ground floor rear

£56k · May '24

Ground floor side infill

£58k · Jun '23

Ground floor rear and ground floor side infill

£77k · Feb '23

Ground floor side infill and internal alterations

£78k · Jun '24

Ground floor rear

£69k · Nov '23

Ground floor rear

£65k · Aug '23

Ground floor rear

£46k · Apr '22

Ground floor rear

£54k · Apr '23

Loft main dormer

£72k · Apr '25

Ground floor rear and internal alterations

£79k · Jun '25

Ground floor rear

£70k · Dec '24

Loft L shaped dormer

£76k · Feb '22

Loft main dormer and two storey side

£72k · Mar '24

Ground floor side infill

£72k · Apr '24

Ground floor side infill

£50k · May '23

Garage conversion

£61k · Jun '23

Ground floor rear

£49k · Jul '22

Ground floor wraparound

£75k · Dec '22

Ground floor rear

£78k · Apr '24

Ground floor rear

£71k · Nov '24

Loft main dormer and garage conversion

£54k · Jan '25

Ground floor rear

£75k · Jun '23

Ground floor rear

£77k · May '24

Ground floor side

£73k · Nov '23

Ground floor rear

£56k · Aug '23

Internal alterations

£40k · May '24

Internal alterations and garage conversion

£64k · Aug '23

Ground floor rear

£73k · Dec '24

Loft main dormer

£64k · Feb '22

Loft L shaped dormer

£75k · Nov '23

Ground floor rear

£62k · Nov '24

Ground floor rear

£42k · Oct '23

Ground floor rear

£54k · Jun '23

Internal alterations

£54k · Jun '23

Ground floor wraparound

£51k · Oct '22

Ground floor wraparound

£78k · Nov '24

Ground floor side infill

£74k · Oct '24

Ground floor rear

£74k · Aug '22

Ground floor rear and internal alterations

£66k · Oct '23

Ground floor rear

£78k · Oct '23

Ground floor rear

£70k · Sep '23

Ground floor rear

£71k · Sep '22

Ground floor rear

£77k · Oct '23

Ground floor side infill

£37k · Nov '23

Ground floor side infill

£59k · Aug '24

Ground floor side infill

£62k · Oct '23

Ground floor rear

£30k · Mar '23

Internal alterations, internal alterations & first floor rear over outrigger

£73k · May '22

Ground floor rear

£49k · May '23

Ground floor rear

£32k · Jun '23

Ground floor rear and internal alterations

£50k · Feb '24

Ground floor rear

£78k · Jul '23

Loft main dormer

£72k · Jan '22

Ground floor side infill

£59k · Jun '23

Ground floor rear

£71k · Mar '24

Ground floor side infill

£62k · Jan '24

Ground floor wraparound

£74k · Aug '22

Ground floor wraparound

£61k · Nov '22

Ground floor rear

£66k · Jul '23

Ground floor side infill, loft outrigger dormer, Loft L shaped dormer & internal alterations

£77k · Jan '22

Loft main dormer

£61k · Jun '23

Ground floor rear

£78k · Aug '23

Ground floor rear

£43k · May '24

Ground floor rear

£72k · Mar '22

Ground floor rear

£74k · Jan '22

Ground floor rear and internal alterations

£70k · Sep '22

Loft main dormer

£71k · Jun '23

Internal alterations and garage conversion

£61k · Sep '22

Ground floor side infill

£65k · Jul '23

Internal alterations

£67k · Apr '22

Internal alterations

£62k · Oct '22

Ground floor rear

£66k · Dec '21

Ground floor wraparound

£79k · Apr '24

Ground floor side infill

£49k · Nov '22

Internal alterations

£26k · Sep '23

Ground floor side infill

£69k · Aug '22

Ground floor side infill

£72k · Jan '22

Ground floor side infill

£39k · Dec '23

Ground floor rear

£61k · Sep '23

Internal alterations and garage conversion

£78k · Jul '22

Loft main dormer

£54k · Oct '24

Ground floor rear

£53k · Nov '22

Ground floor rear

£61k · Feb '23

Internal alterations and internal alterations

£58k · Dec '23

Loft main dormer and internal alterations

£74k · Aug '23

Internal alterations

£55k · Sep '23

Loft main dormer, internal alterations & garage conversion

£76k · Apr '24

Internal alterations

£34k · May '24

Ground floor rear

£68k · Mar '24

Loft main dormer and ground floor rear

£73k · Oct '23

Ground floor rear

£57k · Oct '22

Ground floor rear and internal alterations

£56k · Jun '22

Ground floor wraparound

£72k · Dec '23

Internal alterations

£35k · Jul '22

Ground floor rear

£68k · Oct '23

Loft main dormer, internal alterations, garden annex & internal alterations

£58k · Mar '23

Ground floor rear

£78k · May '23

Ground floor side and rear

£77k · Feb '23

Ground floor side infill and ground floor wraparound

£68k · Mar '23

Ground floor rear and internal alterations

£74k · Jul '22

Internal alterations

£76k · Aug '22

Internal alterations

£60k · May '23

Ground floor side infill

£65k · Dec '23

Ground floor rear

£71k · Oct '22

Ground floor rear

£67k · Dec '23

Loft main dormer

£66k · Feb '23

Ground floor rear

£44k · Jun '23

Ground floor side and rear

£66k · Feb '22

Ground floor side infill

£75k · Apr '23

Ground floor rear

£73k · Jun '23

Ground floor rear and ground floor side infill

£71k · Mar '24

Ground floor wraparound and first floor rear

£63k · May '23

Ground floor side infill

£61k · Aug '23

Internal alterations and internal alterations

£71k · Jun '23

Ground floor rear

£73k · Jul '24

Ground floor rear

£53k · May '22

Ground floor rear

£69k · Oct '23

Ground floor rear

£71k · Aug '23

Ground floor wraparound

£57k · Feb '23

Ground floor side infill and internal alterations

£68k · Jan '24

Ground floor rear

£74k · May '24

Ground floor rear

£66k · Nov '23

Ground floor rear and garage conversion

£65k · May '24

Internal alterations

£28k · Jan '24

Loft hip to gable with main dormer

£75k · Apr '22

Ground floor rear

£74k · Jun '22

Ground floor rear and first floor rear

£70k · May '23

Ground floor rear

£72k · Oct '23

First floor rear

£72k · Nov '23

Ground floor rear

£79k · Mar '22

First floor rear

£53k · May '23

Ground floor rear and internal alterations

£60k · Jan '23

Ground floor rear

£66k · Sep '23

Internal alterations and first floor rear

£75k · Apr '22

Loft L shaped dormer

£71k · Nov '23

Ground floor rear

£63k · Jun '23

Internal alterations and facade alterations

£72k · Sep '22

Ground floor wraparound

£38k · Apr '24

Ground floor rear

£62k · Nov '22

Ground floor side infill

£64k · Mar '24

Two storey side and first floor rear

£77k · Jun '22

Internal alterations

£61k · Mar '22

Ground floor rear

£43k · Aug '24

Garage conversion

£61k · Feb '23

Ground floor side

£43k · Sep '22

Two storey side

£61k · Dec '22

Popular articles

Building Regulations

Downstairs toilet building regulations in the UK – a captivating overview

09 Jul '25 • 5 min read →

Single Storey Extension

Single storey side extensions: everything you need to know

09 Jul '25 • 5 min read →

Single Storey Extension

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

09 Jul '25 • 5 min read →

Kitchen Extensions

7 things to consider when building a kitchen conservatory extension

09 Jul '25 • 8 min read →

Side Return Extensions

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

22 Apr '25 • 6 min read →

Permitted Development

A guide to permitted development rights in 2025

10 Apr '25 • 8 min read →

Planning Permission

Top 10 reasons planning permission is refused

30 Jan '25 • 4 min read →

Conservation Areas

Am I in a Conservation Area?

30 Jan '25 • 3 min read →

Planning Permission

A guide to lawful development certificates

12 Jul '24 • 3 min read →

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

£350k · Jan '24

Ground floor side and garage conversion

£335k · Jun '24

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

£362k · Jan '25

Loft main dormer, internal alterations & two storey rear

£301k · May '24

Airspace new floor

£390k · Feb '24

Loft main dormer, ground floor rear & internal alterations

£308k · Jun '24

Loft main dormer, ground floor rear, loft outrigger dormer & internal alterations

£314k · Mar '24

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

£322k · Sep '24

Ground floor wraparound and first floor side

£323k · Feb '24

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

£346k · Jan '24

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

£372k · Apr '25

Two storey rear and two storey side

£318k · Dec '24

Ground floor side infill and Loft L shaped dormer

£308k · Jun '24

Garden annex, ground floor wraparound & internal alterations

£300k · Nov '24

Garden annex, Loft L shaped dormer & ground floor wraparound

£321k · Oct '22

Ground floor rear

£338k · Jul '24

Ground floor side infill and first floor rear over ground floor

£321k · Sep '24

Internal alterations, airspace new floor & facade alterations

£435k · Jan '24

Internal alterations, internal alterations & facade alterations

£328k · Sep '22

Ground floor rear, ground floor front & internal alterations

£329k · Sep '24

Loft main dormer, ground floor wraparound & garage new build

£434k · Oct '24

Internal alterations and ground floor wraparound

£319k · May '22

View nearby planning applications

Find out what your local planning authority has approved recently View applications

Share your feedback

Would you recommend this tool to others?

Contact

+44 208 068 4811 [email protected]

Locations

Popular Locations House Prices

Design

Design & Planning

Connect

Building Contractors Structural engineers Building control approvers CCTV drainage surveyors Party wall surveyors

Finance

About Resi finance Find a loan

Portfolio

Kitchen Bedroom Bathroom Garden Facade Ground floor First floor Loft

Resources

Advice centre FAQs House extensions: everything a homeowner needs to know Loft Conversion Costs UK 2025: A Complete Guide to Budgeting Your Build House extension without planning permission: what are the rules? How much does a side return extension cost? A guide to permitted development rights in 2025

Free tools

Project cost calculator Permitted development quiz Home value estimator

Company

About us Careers Resi foundation Beam partnership Terms of use Privacy policy

Partners

Tradesperson sign up

Resi

Copyright © 2022 Resi Design Ltd.

Resi Design Ltd. trading as 'Resi' | Company No: 10471125

We are proud to employ architects registered with the Architects Registration Board and were awarded the mark for The Mayor's Good Work Standard for fair pay & conditions, wellbeing, skills, progression, diversity and recruitment.