As moving gets more and more expensive, people are looking to improve their homes rather than go through the hassle of trying to find a cheap mortgage and spend money on stamp duty. One way to improve your home and give you more space is to build a single storey extension.

On average, a single storey extension costs £1,800-£3,000 per square metre to build – but a number of factors can affect the cost. Let’s take a deeper look into how much a single storey extension costs.

Cost to build a 20m2 single storey extension in the uk

How much does a single storey extension cost?

A single storey extension is a ground-floor extension that is usually built at the back or the side of a property, although these are often called side return extensions. People often use single storey extensions to extend their kitchen, create a second living room or add a study to their homes.

For an average 20 square metre single storey extension, expect it to cost anywhere between £36,000 and £60,000. This price includes labour and materials, but usually won’t include decorating or plastering.

HaMuch has a large database of hourly and daily rates for extension builders across the country, so make sure you take a look at our table further down the page to get an idea of how much the average single storey extension will cost in your area.

The larger you build your extension, the more likely it is that you will make some savings on material costs. Here’s how much to expect to spend on larger extensions:

30 square metres: £54,000-£84,000

40 square metres: £70,000-£104,000

50 square metres: £90,000-£125,000

Single storey extension cost calculator

When you decide build a single storey extension, you need to be aware of other costs involved. While our price estimates above include all your internal stud walls, utilities, electrics, windows and doors, there are some costs that won’t be included.

Our cost calculator below can help you work out the total cost of your single storey extension:

Job type

Average cost

Single storey house extension

£1,800-£3,000 per square metre

Plastering

£10 per square metre, plus £100-£150 per day

Painting and decorating

£9-£18 per square metre (not including paint)

Carpet fitting

£5-£10 per square metre (installation only)

Wooden flooring installation

£20-£30 per square mere (fitting only)

What size single storey extension can I build without planning permission?

Single storey extensions are permissible under permitted development rights, meaning you don’t have to apply for planning permission. There are different rules for side extensions and rear extensions:

Side extensions

  • Must have a maximum height of 4 metres

  • Must not exceed half the width of the original house

  • Must not face the road

Rear extensions

  • Must not be longer than the rear wall of the original house by more than 3 metres for a semi-detached house, or 4 metres for a detached house

  • Must not exceed 4 metres in height

You can also use a rule called ‘prior approval’ to double your allowance for a single storey extension, allowing you to build a single storey extension of up to 6 metres for a semi-detached house or 8 metres for a detached house.

Do I need an architect for an extension?

There’s no law to say that you have to have an architect to build an extension. If your single storey extension is a simple extension with no special eco features or no party wall issues, you might be able to get away with not employing an architect.

However, it’s always good to have designs or drawings done before you start an extension project. You can hire architectural designers that cost slightly less than a registered architect to help you design the best extension based on your budget, advising you where you can save money. They can also help you with planning permission applications, building regulations and more, so it might still be worth looking for someone to advise you.

How deep do foundations need to be for a single storey extension?

Your builder should have all this in hand, but for a single-storey extension using strip foundations, the concrete foundation base should be a minimum of 150mm. The trench itself should be at least 1 metre deep with the brickwork sitting on top to make it up to 50mm.

If you have trees near your property, you may need to have deeper foundations. The general rule is if you have a tree within 30 metres of where you want your single storey extension, your foundations will need to be deeper. This is because deep roots can affect the moisture in the soil that supports your property.

Is it cheaper to have an extension or a conservatory?

It’s normally cheaper to build a conservatory than an extension, because you usually don’t have to apply for any type of planning permission and may not have to have building regulations sign-off. However, it’s worth remembering that a conservatory isn’t as versatile as an extension. Conservatories are made mostly of double glazing, so they can get very hot in the summer months. In the winter, they can be too cold to enjoy because they’re poorly insulated.

If you want to use your new single storey extension all year round, you might consider that an extension is more cost effective as you’ll get more use out of it. It’ll also depend on what you want to use your room for – for example, if you want your extension to be a bedroom, a conservatory won’t be suitable. However, if you want it to be an extension of your kitchen, a conservatory could offer good value for money.

If you’re ready to kick off your single storey extension project, post your job on HaMuch now to get in touch with available builders in your area that can give you a quote.


Estimates for common extension builder jobs;

Job Estimate
Cost to build a single storey extension £50000
Cost to build a side return extension £61000
Cost of a loft conversion £43000
Basement conversion cost £43000

Rates for other trades

Single storey extension cost in the UK
Single storey extension cost in the UK (excluding VAT or callout charges)
Location in UKSingle storey extension cost
Single storey extension near Aberdeen£49360
Single storey extension near Amber Valley£43440
Single storey extension near Angus£44560
Single storey extension near Arun£44880
Single storey extension near Ashfield£43920
Single storey extension near Aylesbury Vale£46640
Single storey extension near Barnsley£46160
Single storey extension near Basildon£45680
Single storey extension near Basingstoke & Deane£46800
Single storey extension near Bassetlaw£44240
Single storey extension near Bath & North East Somerset£45520
Single storey extension near Bedford£48400
Single storey extension near Belfast£31600
Single storey extension near Birmingham£41360
Single storey extension near Blackburn£41040
Single storey extension near Blackpool£39120
Single storey extension near Bolton£41200
Single storey extension near Bournemouth£45680
Single storey extension near Bracknell Forest£48080
Single storey extension near Bradford£41680
Single storey extension near Braintree£44880
Single storey extension near Breckland£39920
Single storey extension near Bridgend£40080
Single storey extension near Brighton£44560
Single storey extension near Bristol£45360
Single storey extension near Broadland£38480
Single storey extension near Broxtowe£43280
Single storey extension near Bury£41680
Single storey extension near Caerphilly£39760
Single storey extension near Calderdale£40720
Single storey extension near Cambridge£47440
Single storey extension near Canterbury£41520
Single storey extension near Cardiff£39920
Single storey extension near Carmarthenshire£40080
Single storey extension near Charnwood£40560
Single storey extension near Chelmsford£45680
Single storey extension near Cheltenham£45200
Single storey extension near Cherwell£46160
Single storey extension near Chester£41520
Single storey extension near Colchester£42480
Single storey extension near Conway£38640
Single storey extension near Coventry£40720
Single storey extension near Crewe & Nantwich£42960
Single storey extension near Dacorum£47600
Single storey extension near Derby£43280
Single storey extension near Doncaster£43920
Single storey extension near Dover£41040
Single storey extension near Dudley£41040
Single storey extension near Dumfries & Galloway£35280
Single storey extension near Dundee£45520
Single storey extension near East Ayrshire£41840
Single storey extension near East Devon£39760
Single storey extension near East Dunbartonshire£43920
Single storey extension near East Hampshire£45680
Single storey extension near East Hertfordshire£48240
Single storey extension near East Lindsey£39440
Single storey extension near East Riding£42000
Single storey extension near Eastleigh£44080
Single storey extension near Edinburgh£47600
Single storey extension near Elmbridge£47920
Single storey extension near Epping Forest£47600
Single storey extension near Erewash£42960
Single storey extension near Exeter£39760
Single storey extension near Falkirk£42800
Single storey extension near Fife£47920
Single storey extension near Flintshire£41040
Single storey extension near Gateshead£43600
Single storey extension near Gedling£43440
Single storey extension near Glasgow£46000
Single storey extension near Gloucester£43760
Single storey extension near Guildford£48880
Single storey extension near Gwynedd£34480
Single storey extension near Halton£41040
Single storey extension near Harrogate£41200
Single storey extension near Havant & Waterloo£44240
Single storey extension near Highland£40400
Single storey extension near Horsham£46320
Single storey extension near Huntingdonshire£48240
Single storey extension near Ipswich£41200
Single storey extension near Isle of Wight£44080
Single storey extension near Kings Lynn & West Norfolk£42160
Single storey extension near Kingston-upon-Hull£41360
Single storey extension near Kirklees£41680
Single storey extension near Knowsley£40080
Single storey extension near Lancaster£40400
Single storey extension near Leeds£41680
Single storey extension near Leicester£39600
Single storey extension near Lisburn£31760
Single storey extension near Liverpool£40240
Single storey extension near London£47600
Single storey extension near Luton£47120
Single storey extension near Macclesfield£42160
Single storey extension near Maidstone£46800
Single storey extension near Manchester£41680
Single storey extension near Mid Bedfordshire£48080
Single storey extension near Mid Sussex£45200
Single storey extension near Middlesbrough£42960
Single storey extension near Milton Keynes£47120
Single storey extension near Neath Port Talbot£40720
Single storey extension near New Forest£45520
Single storey extension near Newbury£46480
Single storey extension near Newcastle-under-Lyme£41360
Single storey extension near Newcastle-upon-Tyne£43600
Single storey extension near Newport£40720
Single storey extension near North Ayrshire£43760
Single storey extension near North East Lincolnshire£42320
Single storey extension near North Hertfordshire£47920
Single storey extension near North Lanarkshire£43440
Single storey extension near North Lincolnshire£40080
Single storey extension near North Somerset£45360
Single storey extension near North Tyneside£44080
Single storey extension near North Wiltshire£43920
Single storey extension near Northampton£45040
Single storey extension near Norwich£38640
Single storey extension near Nottingham£43440
Single storey extension near Nuneaton & Bedworth£41200
Single storey extension near Oldham£41840
Single storey extension near Oxford£46800
Single storey extension near Pembrokeshire£31920
Single storey extension near Perth & Kinross£46640
Single storey extension near Peterborough£46960
Single storey extension near Plymouth£43280
Single storey extension near Poole£46000
Single storey extension near Portsmouth£44240
Single storey extension near Powys£37680
Single storey extension near Preston£40560
Single storey extension near Reading£48080
Single storey extension near Redcar & Cleveland£43440
Single storey extension near Reigate & Banstead£47760
Single storey extension near Renfrewshire£47280
Single storey extension near Rhondda, Cynon, Taff£40080
Single storey extension near Rochdale£41680
Single storey extension near Rotherham£46800
Single storey extension near Salford£41360
Single storey extension near Salisbury£49200
Single storey extension near Sandwell£41040
Single storey extension near Scarborough£41200
Single storey extension near Scottish Borders£49200
Single storey extension near Sefton£40240
Single storey extension near Sevenoaks£47120
Single storey extension near Sheffield£47440
Single storey extension near Slough£48240
Single storey extension near Solihull£40880
Single storey extension near South Ayrshire£42480
Single storey extension near South Bedfordshire£48400
Single storey extension near South Cambridgeshire£48080
Single storey extension near South Gloucestershire£45360
Single storey extension near South Kesteven£40880
Single storey extension near South Lanarkshire£42320
Single storey extension near South Oxfordshire£47120
Single storey extension near South Somerset£45840
Single storey extension near South Tyneside£43760
Single storey extension near Southampton£44080
Single storey extension near Southend-on-Sea£44560
Single storey extension near St Albans£48080
Single storey extension near St Helens£40240
Single storey extension near Stafford£42000
Single storey extension near Stockport£42000
Single storey extension near Stockton-on-Tees£43440
Single storey extension near Stoke-on-Trent£41360
Single storey extension near Stratford-on-Avon£41360
Single storey extension near Stroud£43600
Single storey extension near Suffolk Coastal£40880
Single storey extension near Sunderland£43600
Single storey extension near Swale£44240
Single storey extension near Swansea£41840
Single storey extension near Tameside£42000
Single storey extension near Teignbridge£41360
Single storey extension near Tendring£41680
Single storey extension near Test Valley£43760
Single storey extension near Thamesdown£43440
Single storey extension near Thanet£39440
Single storey extension near The Wrekin£43120
Single storey extension near Thurrock£46640
Single storey extension near Torbay£42320
Single storey extension near Trafford£42000
Single storey extension near Vale of Glamorgan£40880
Single storey extension near Vale of White Horse£45680
Single storey extension near Vale Royal£41520
Single storey extension near Wakefield£42000
Single storey extension near Walsall£41360
Single storey extension near Warrington£41680
Single storey extension near Warwick£40720
Single storey extension near Waveney£39440
Single storey extension near Waverley£49040
Single storey extension near Wealden£44880
Single storey extension near West Lancashire£39920
Single storey extension near West Lothian£45840
Single storey extension near West Wiltshire£43920
Single storey extension near Wigan£40720
Single storey extension near Windsor & Maidenhead£48240
Single storey extension near Wirral£40560
Single storey extension near Wokingham£48080
Single storey extension near Wolverhampton£41040
Single storey extension near Wrexham Maelor£42000
Single storey extension near Wychavon£42000
Single storey extension near Wycombe£47920
Single storey extension near York£40560