House extension cost
How much does it cost to extend a house?
You could be better off thinking about building an expansion rather than moving because UK property prices are rising! Our guide goes over worker costs, schedules, material costs, and more!
Continue reading for a more detailed guide.
What is the price of an extension?
Now let’s get right to it!
The typical cost of a house addition is between £125,000 and £22,500. That’s a really wide pricing range, but bear with us while we clarify:
The kind of extension you select, its size, and the finish quality will all affect how much it will cost.
People who live in or near London can expect to pay more for work.
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For example, the cost of a single-storey extension would be between £22,500 and £125,000. Usually, this kind of extension is used for modest improvements like bathrooms or enlarging living rooms or kitchens.
Let’s take a closer look at that pricing range, as it’s still quite large.
The average cost of a small, single-storey expansion (15 m2) ranges from £22,500 to £37,500, primarily depending on your location and the final quality.
On the other hand, the price of a sizable (50 m2) single-storey addition might range from £75,000 to £125,000.
In the end, the amount you end up spending on the extension will depend heavily on the room type and finish you choose.
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Another option would be to get a double extension. Because it’s two storeys tall, you can use it to enlarge your living quarters on the main and second floors of your house. A double addition might cost anywhere from £45,000 to £245,000.
It is difficult to put a small price range on home additions, as you can see.
We can put you in touch with local builders who can give you a more precise quote for your home extension.
Home Extension Costs
Want to know how much it will cost to build an addition onto your house?
Let’s dig it a bit.
Estimate for a One-Storey Extension
Commonly built to enlarge the first-floor living or kitchen area, a one-storey extension is a common type of home extension.
The price range for a single-storey addition is roughly £1500m2 to £2500m2.
You can see the range of prices for basic, moderate, and premium quality single-storey extensions in the table below, broken down by size.
| Size (m²) | Basic | Average | Premium |
|---|---|---|---|
| Small (15m²) | £26,250 | £31,500 | £37,500 |
| Medium (25m²) | £43,750 | £52,500 | £62,500 |
| Large (50m²) | £87,500 | £105,000 | £125,000 |
A Double-Storey Extension Price
An additional room or rooms can be added to your home with a double-storey extension, which spans double-storeys and provides more living space for your family.
The price per square metre for a double-storey extension ranges from £1500 to £2450.
Prices for double-storey extensions of varying sizes and quality are detailed in the table below.
| Size (m²) | Basic | Average | Premium |
|---|---|---|---|
| Small (30m²) | £51,000 | £61,500 | £73,500 |
| Medium (60m²) | £102,000 | £123,000 | £147,000 |
| Large (100m²) | £170,000 | £205,000 | £245,000 |
Cost of a Rear Extension
At the back of a house, where there is a big yard, a rear extension is added.
It costs about £1500 to £2500 per square metre to add on to the back wall.
Prices for basic, average, and luxury rear extensions of different sizes can be found in the table below.
| Size (m²) | Basic | Average | Premium |
|---|---|---|---|
| Small (15m²) | £26,250 | £31,500 | £37,500 |
| Medium (25m²) | £43,750 | £52,500 | £62,500 |
| Large (50m²) | £87,500 | £105,000 | £125,000 |
Cost of Side Extension
People often choose side extensions when they have a lot of room on the left or right side of their home.
Most of the time, side additions cost between £2,000 and £4,000 per m².
Here is a table that shows the different sizes of houses for basic, average, and premium side extensions.
| Size (m²) | Basic | Average | Premium |
|---|---|---|---|
| Small (20m²) | £40,000 | £60,000 | £80,000 |
| Medium (40m²) | £80,000 | £120,000 | £160,000 |
| Large (60m²) | £120,000 | £180,000 | £240,000 |
Cost of Side-return Extension
A side return extension might be useful for homes that have a small area on the side that they use to store things like bins, bikes, and other things.
An extra room with a side return costs between £2,000 and £4,000 per square metre.
The prices of basic, medium, and premium side-return extensions are shown in the table below.
| Size (m²) | Basic | Average | Premium |
|---|---|---|---|
| Small (6m²) | £12,000 | £18,000 | £24,000 |
| Medium (9m²) | £18,000 | £27,000 | £36,000 |
| Large (12m²) | £24,000 | £36,000 | £48,000 |
Kitchen extension costs
Are you dreaming of a more spacious kitchen for your house?
A kitchen expansion could be the way to go for you.
With the addition of the kitchen installation costing an additional £200 to £1000 per m², the total cost would be between £1500 to £2500 per square metre, which is comparable to a single-storey extension.
| Size (m²) | Basic | Average | Premium |
|---|---|---|---|
| Small kitchen extension (6m²) | £14,450 | £17,400 | £26,900 |
| Medium kitchen extension (9m²) | £21,175 | £25,100 | £35,350 |
| Large kitchen extension (18m²) | £37,350 | £45,200 | £57,700 |
| Small kitchen suite (6m²) | £5,000 | £6,000 | £14,000 |
| Medium-sized kitchen suite (9m²) | £7,000 | £8,000 | £16,000 |
| Large kitchen suite (18m²) | £9,000 | £11,000 | £19,000 |
How much does a bathroom extension cost?
If you’re short on space or just want more bathroom space, an addition to your current home is a great option.
House extension prices with a bathroom are based on prices for single-storey extensions. Because of this, the total cost, including the installation of the bathroom, is approximately £300 to £3000 per square metre, or £1500 to £2500 per square metre.
The prices to install bathroom additions of varied sizes and quality are detailed in the table below.
| Size (m²) | Basic | Average | Premium |
|---|---|---|---|
| Small bathroom extension (3m²) | £5,400 | £10,950 | £16,500 |
| Medium bathroom extension (6m²) | £10,8000 | £21,900 | £33,000 |
| Large bathroom extension (9m²) | £17,100 | £22,100 | £27,000 |
| Small bathroom suite (3m²) | £900 | £4,950 | £9,000 |
| Medium-sized bathroom suite (6m²) | £1,800 | £9,900 | £18,000 |
| Large bathroom suite (9m²) | £2,700 | £14,850 | £27,000 |
Price of a porch extension
Improving your home’s front entryway is easy with a porch expansion.
Porch additions often range in price from £300 to £2000 pounds per square metre.
Porch extensions made of uPVC, wood, aluminium, and brick are priced differently, as shown in the table below.
| Size (m²) | uPVC | Wood | Aluminium | Brick |
|---|---|---|---|---|
| Small porch extension (3m²) | £1,500 | £2,700 | £6,000 | £6,000 |
| Medium porch extension (6m²) | £3,000 | £5,400 | £12,000 | £12,000 |
| Large porch extension (9m²) | £4,500 | £8,100 | £18,000 | £18,000 |
Cost of a Prefab Extension
Short on funds?
Because it is already built before installation, a prefab extension can save you a lot of money on labour, making it a good choice if your budget is tight.
A prefab addition will typically cost between £1200 and £1700 per square metre.
The prices for standard, average, and premium prefab additions are detailed in the table below.
| Size (m²) | Basic | Average | Premium |
|---|---|---|---|
| Small prefab extension (15m²) | £18,000 | £21,800 | £25,500 |
| Medium prefab extension (25m²) | £30,000 | £36,300 | £42,500 |
| Large prefab extension (35m²) | £42,000 | £50,800 | £59,500 |
Wrap-around extension costs
The largest kind of home addition is the wrap-around, which often attaches to the back and sides of the house.
The typical price range for a wrap-around extension is £2,000 to £4,000 per square metre.
Below is a table that displays the pricing of various sized wrap-around extensions on three different budgets: basic, average, and premium.
| Size (m²) | Basic | Average | Premium |
|---|---|---|---|
| Small wrap-around extension (20m²) | £40,000 | £60,000 | £80,000 |
| Medium wrap-around extension (40m²) | £80,000 | £120,000 | £160,000 |
| Large wrap-around extension (60m²) | £120,000 | £180,000 | £240,000 |
How much does it cost to add an extension?
When building an addition, what other costs might you need to think about?
Let’s get to that right away.
Costs of an extension architect
You might want to hire an architect to help you plan and create your new addition and make sure it follows all building codes.
It costs about £50 to £100 an hour to hire an architect.
Groundwork costs for a long extension
It’s important to make sure the ground is ready before building an addition.
This will make sure that the increase is built on a strong base and also keep problems from happening in the future.
It might be necessary to dig up the ground if it isn’t level. It might cost between £30 and £50 per cubic metre.
Installing drains is another large-scale type of groundwork. To make sure that your new addition drains properly, this could mean taking out old pipes and putting in new pipes and drains.
It costs between £550 and £1800 to put in new drains.
Costs of extension planning permits
Before you start building an addition, you should make sure that your plans follow the rules for getting planning permission. This will keep you from having to pay about £200 for an application.
To keep from having to pay extra, you should make sure that your extension fits these requirements:
- You can’t add on to the property that takes up more than half of its land.
- The height of the addition can’t be higher than the roof on the current building. If an addition is less than two metres from the property line, the eaves should not be higher than three metres.
- Putting in raised platforms, balconies, chimney flues, vent pipes, or any work to the roof (including cladding) is not part of the job.
- Side additions can only have one storey and can’t be taller than four metres from the side elevation.
- Any extensions to the side of a building can’t be wider than half of the building itself.
- Single-storey rear additions can’t go past the back wall of a separate home more than four metres, or three metres for any other type of home.
- Extensions with two storey’s can’t be more than four metres from the back wall of the house and can’t be closer than seven metres to a property line.
- A two-storey addition must have a roof pitch that is as close as possible to the current house.
- If the windows on the side of a double-storey addition are on the top floor, they all need to be obscure-glazed.
Costs of Building Regulation Extensions
Most home additions do need to be approved by the building rules before they can be built.
How much does this cost?
Different local governments charge different amounts for building rules approval, so the price will depend on where you live.
There are several parts of an extension that need to be approved by a professional before the house can be considered safe.
Among these are:
- Walls inside and outside
For some extensions, the outside walls need to be built below grade to make sure the building is supported properly.
The foundation, which is usually made of blocks and mortar or brick, will be made up of the new walls that are built. This is very important for protecting the whole structure: the base needs to be able to handle frost and underground materials.
- Flooring
A strong structure that can hold a lot of weight is important for the flooring you put in your addition to make sure it meets building standards.
It should also be resistant to heat and water so that the extension flooring stays warm, airy, and safe from dampness, weed growth, and shrinkage.
- Ventilation
Ventilation is one of the most important things you need to think about when adding on an extension. This will make the air in your home healthier and better for you.
Adding windows is an easy way to let air flow through your home, especially in places that don’t get much air flow, like the bathroom. You can also use it on window frames to add trickle air to every room in your house.
- Foundations
It’s important to have strong supports (usually made of concrete) in place before adding on.
The earth should be strong enough to support the weight of the foundations and the extra building. Also, it should be dug deep enough so that movement and contracting don’t change the length. This is especially important for an addition with two storeys, since it needs more soil and structures to be stable.
What are the costs of extension supplies?
Planning to add on yourself? Or maybe you just want to get the things you need.
You’ll need to think about the following supply prices in this case:
| Supply description | Average supply cost |
|---|---|
| Skirting board | £3 to £40 per m² |
| Plasterboard | £5 to £15 per m² |
| Wood flooring | £30 to £85 per m² |
| Laminate flooring | £10 to £55 per m² |
| Wall tiles | £12 to £160 per m² |
| Floor tiles | £15 to £50 per m² |
| Paint | £3 to £20 per litre |
| Plug sockets | £1 to £200 per socket |
| Light switches | £1 to £200 per switch |
| Radiators | £20 to £320 |
| Underfloor heating | £50 to £150 per m² |
| Internal doors | £90 to £750 |
| External doors | £120 to £4000 |
| Windows | £200 to £3000 |
| Door handles | £3 to £220 |
| Light fittings | £2 to £600 per light |
Costs of hiring a tradesman for an extension
Another important thing.
You will need to add up the wage costs of all the tradespeople who will be working on your home extension when you figure out how much the whole project will cost.
Now let’s go through them.
Extension Builder Cost
When building an addition, builders do one of the most important jobs.
They are helping to build the extension’s foundations and frame to make sure it is strong and stable.
It costs about £130 to £280 per day, or £16 to £46 per hour, to hire a builder to help you add on to your home.
Cost of an Extension Plumber
If you’re adding on to your kitchen or bathroom, you will need to hire a plumber to put in sinks, toilets, tools and other things.
From £200 to £400 per day for a full bathroom, or £30 to £60 an hour to plumbed a sink, plumbers charge a lot.
Cost of an Extension Electrician
Before you can add lights and electrical tools to your extension, you will need to hire a professional electrician to make sure everything is safe and works right.
The normal rate for an electrician is between £30 and £60 an hour, or £170 and £340 a day.
Cost of an Extension Plasterer
He or she will need to prepare your walls and make sure that any paint or wallpaper lasts.
To plaster your new addition, you can expect to pay between £150 and £220 per day. To re-plaster walls, they might only charge £10 to £20 an hour.
Cost of an Extension Painter and Decorator
After the plastering is done, you will need to hire a painter to paint or put up wallpaper on the inside and outside walls of your new home extension.
Most tradespeople charge between £15 and £40 an hour to paint one or more walls.
It costs between £100 and £300 a day for more than one room.
Cost of an Extension Carpenter
If you want to add on an extension, you should hire a professional builder to help you build it and put it up.
It costs about £150 to £250 a day to hire a carpenter.
You might also hire them to do smaller jobs, like putting in a new door frame. In this case, they’ll most likely charge you between £20 and £40 an hour.
Cost of an Extension Kitchen Fitter
If you’re adding on to your kitchen, you might want to hire a kitchen builder to put in your cabinets and countertops.
Your hourly rate should be between £10 and £20 for a small kitchen. For a big kitchen, your daily rate could be between £120 and £200.
Cost of an Extension Window Fitter
After building the addition, you should hire a professional window fitter to put in windows that are fully sealed.
You can expect to pay between £25 and £35 an hour for one or two windows.
You can expect to pay around £250 to £350 per day for a full set of windows on a double-storey extension.
Cost of an Extension Labourer
A labourer is another important tradesperson you may need to hire. They will help with most of the work on-site, such as building the foundations, the extra structure, and more.
A worker makes between £100 and £160 a day, or £7 to £15.00 an hour.
Cost of an Extension Bricklayer
You will need to hire an experienced builder who knows what they’re doing to make sure your extension is built correctly.
Large extensions cost about £130 to £180 per day, while door extensions cost about £12 to £20 per hour.
How long does a house extension take?
It can take a lot of time to build an addition.
For this reason, it’s important to know how long it will take to build the type of extension you want. In short, here’s how long it will take to finish a house extension by type:
| Extension type | Duration |
|---|---|
| Single-storey extension | 2 to 3 months |
| Double-storey extension | 4 to 6 months |
| Side extension | 2 to 3 months |
| Side return extension | 1 to 2 months |
| Rear extension | 2 to 4 months |
| Wrap-around extension | 4 to 6 months |
| Kitchen extension | 2 to 6 months |
| Bathroom extension | 2 to 4 months |
| Prefab extension | 8 to 10 weeks |
| Porch extension | 3 to 14 days |
How much does each part of an extension cost?
There are several steps that go into making an addition.
There are costs for each of these steps that you need to know about and plan for.
Let’s start with them.
Rules for building and design
What should come first? First, you’ll need to make sure that the design of your addition follows the rules for building regulations and planning approval. What if, though, your current plans don’t work with the rules?
That means you will either have to change your plans or pay at least £200 to get your extension accepted.
Once you have permission, you can make more detailed plans for your extension.
You will need the help of a planner for this. Their main job is to make plans for the building, which include how big the extra room will be and how it should look. During the whole process, they have to make sure they follow the rules.
Most of the time, architects charge between £50 and £100 an hour.
Groundwork and foundations
A lot of work needs to be done on the ground before any building can begin.
Because it requires digging, this process can be pricey. The total cost will rely on how big the land is where you’re working. It can range from £30 to £50 per cubic metre.
You might also have to take out pipes and put in new drains. In addition to protecting your addition from damage and flooding, this will also make sure that water flows to and from the main house if it needs to. The price range for this job is usually £550 to £1800.
After all the planning is done?
That’s the only way to make sure the foundations are strong enough for the extension to be built on. Putting in the foundations takes a lot of time and usually costs between £100 and £130 per cubic metre.
Forming the Outside
What comes next after everything is ready and the base is set?
In the next step, the outside frames and walls are built using bricks, blocks, tiles, and wood.
Professionals charge about £800 to £1600 per square metre to build a weatherproof extension shell. This includes the cost of the shell itself.
Fixtures and Parts
Adding the last few details is what the last stage is all about.
This will include putting in furniture, such as kitchen cabinets and countertops, which will cost around £5000 to £19,000.
If you want to add on to your bathroom, new bathroom fixtures will cost between £900 and £27,000.
Your windows and doors will also be put in at this point. The cost is between £250 and £1200 per window. The cost of installing a door is between £50 and £120 per door.
At this point, you’ll also want to put in indoor and outdoor lighting, which will cost between £60 and £1000 if done by a trained electrician.
What is the cost of a roof extension?
The roof is one of the most important parts of an addition to a house. You can pick from a few different kinds of roofs, though. Let’s talk about them now.
Dual-pitched extension roof price
A simple type of roof with two slopes that meet at the top is called a duo-pitch roof or a gabled roof.
The price range for two-pitch extension roofs is usually between £2,000 and £4,500.
Cost of a flat roof extension
The only thing that makes a flat roof different from other types of roofs is a small slope that lets water drain off.
The price of a flat extra roof ranges from £1500 to £3000.
Cost of Catslide Roof Extension
A catslide roof is a type of pitched roof where one side slopes down more than the other.
In general, a catslide roof costs around £1200 per square metre.
Cost of a mono-pitch extension roof
A roof with only one slope is called a mono-pitch roof or a lean-to roof. This is still one of the least expensive ways to fix a roof.
A mono-pitch extension roof usually costs between £2,000 and £3,200 to have put on.
Cost of a Hipped Extension Roof
A hipped roof has four sloped sides that are all the same length and meet at a point in the middle. In general, a hipped extension roof costs between £1250 and £7250.
Price to Take Down an Extension
What if you want to get rid of an old extension? How much does that cost?
You might want to hire professionals to make sure the growth takes off correctly. It will cost between £500 and £3000.
Besides that, getting rid of the trash will cost between £70 and £300.
FAQS
How near may I build an extension to my boundary?
When building a double-storey extension, stay 7 metres from the boundary.
Other extensions within two metres of the boundary cannot exceed three metres of the property’s eaves.
How much does a house extension add value to your home?
Adding an extension to your home can give you a return on your investment of up to 23% for an extra bedroom and en-suite, and up to 6% for a bathroom extension.
What is the largest size of extension you are allowed to build?
If you want to save money on getting building and planning clearance, you should only build an addition that meets the requirements for permitted development.
If you want to add a single-storey rear addition, it shouldn’t go deeper than 3 to 4 metres. Some extensions can go up to 6 metres, and homes that aren’t attached to anything else can go up to 8 metres.
When adding a single-storey, how deep do the footings need to be?
The roots for a single-storey addition must be at least 200 mm deep to make sure the building is safe and strong.
What are the average costs for a house extension in London?
The cost of a house extension in London typically ranges from £1,500 to £3,000 per square metre, depending on the type of extension, materials, and location within London. More complex projects or higher-end finishes may drive the price up further.
What factors influence the cost of a house extension in London?
Several factors can affect the cost of your extension, including:
· Size and complexity of the project.
· Quality of materials and finishes.
· Location within London (costs are often higher in central areas).
· Type of extension, such as rear, side, or wraparound.
· Structural changes required (e.g., removing load-bearing walls).
· Planning permissions and building regulations requirements.
How much does a single-storey extension cost?
For a single-storey extension in London, costs generally start at around £1,500 per square metre for a basic finish, and can reach up to £2,500 per square metre for more complex designs and high-quality materials.
How much does a double-storey extension cost?
A double-storey extension tends to cost slightly less per square metre on the second floor since the foundation and roofing costs are already covered. Expect prices around £2,000 to £3,000 per square metre for a double-storey extension in London.
Are there any additional costs I should be aware of?
Yes, additional costs might include:
· Planning application fees (if applicable): typically £200–£300.
· Architect fees: approximately £1,000–£5,000 depending on the complexity.
· Structural engineer fees: around £1,000–£2,500.
· Party Wall Agreement costs (if your extension affects adjoining properties): £1,000–£2,000.
· VAT at 20% unless your home is exempt.
Do I need planning permission for my extension?
In some cases, you can extend your home under Permitted Development Rights, but larger extensions or those in protected areas (e.g., conservation zones) may require planning permission. The cost of planning permission is typically £200–£300.
What is the difference between a basic, mid-range, and high-end finish?
· Basic finish: Functional and cost-effective materials (e.g., standard flooring, basic fixtures) typically cost £1,500–£2,000 per square metre.
· Mid-range finish: Improved quality with a mix of durability and aesthetics, costing £2,000–£2,500 per square metre.
· High-end finish: Premium materials, bespoke features, and luxury finishes, with costs upwards of £2,500–£3,000+ per square metre.
How long does it take to complete a house extension?
A small to medium-sized extension typically takes 3–6 months to complete. Larger, more complex extensions can take 6–12 months, depending on factors like planning approval, structural work, and weather conditions.
How can I keep costs down when extending my home in London?
To reduce costs:
· Opt for a simpler design (e.g., rectangular or square).
· Use standard materials and avoid custom or bespoke options.
· Keep the structure sound to avoid costly structural changes.
· Plan ahead to avoid unexpected costs or delays.
Are house extensions a good investment in London?
House extensions are often a smart investment in London due to high property values. A well-designed extension can add 10–20% to your home’s value, particularly if you add additional living space, bedrooms, or a kitchen.
Can I finance my house extension?
Many homeowners finance their extensions through:
· Remortgaging their property.
· Taking out a home improvement loan.
· Using savings or other financial resources.
· Consult a financial advisor to determine the best financing option for your situation.
How can I find a reliable contractor for my house extension in London?
Look for contractors with:
· Good reviews and references.
· Proper insurance and certifications.
· Experience in similar projects.
· Consider companies like Buildify Ltd, which is regarded as one of the top builders for loft conversions and house extensions in London.
Will my extension be affected by building regulations?
Yes, all extensions must meet UK building regulations, covering aspects such as structural integrity, energy efficiency, fire safety, and accessibility. Ensure your contractor handles compliance to avoid penalties or issues during resale.
