Eco Building Ltd

Cost Of House Extension in London


Full Guide To House Extension Costs In London

Get a clear picture of how much you’ll need to budget for your home extension with this comprehensive look at expenses, including: types of expansions, administrative charges, and so much more!

Homeowners who are searching for a way to improve their living space have several choices available, yet none as popular as home extensions. With the mounting demand for larger, flexible and practical homes, an ever-increasing number of people are turning to extending in order to get that exciting new lease on life they so desire. But what is the typical cost associated with house extension projects?

When considering the cost of an extension to your home, remember that it can be highly variable and is dependent on numerous factors such as size, location, type of extension chosen. For example, a single-story addition in Scunthorpe will differ greatly from a two-story expansion in London – and this article aims to provide insight into how much you can expect for various projects across different locations. In this article, we’ll cover all the essential details regarding home extension costs and provide answers to questions like:

The average costs of different types of house extensions in London
Additional factors that affect the cost of a house extension
How to search for reputable contractors
How to decrease costs while building your extension


How much does a house extension cost?

Single storey extensions average cost per square meter in London

Single storey extensions, as the name suggests, are usually constructed on a single floor and can be rear-facing, side-facing or wrap around. A single-story house extension costs anywhere between £2,200 and £3,300 per square meter

Ground floor rear house extension average cost In London

Rear extensions are an extremely sought-after type of extension, as they expand the back area of your dwelling and flow into your outdoor space.

Contractor TypeLow-end EstimateHigh-end Estimate
Budget£45,000£75,000
Average£54,600£90,000
Premium£58,500£97,500

(for a 30 sqm extension)
For a bespoke quote call us on 0207 859 4225


Ground floor side return extension average cost In London

Side return extensions, also known as ‘side infills’, are a great option for those who want to make use of the dead alleyway space present on Victorian and period terrace homes. Unlike rear extensions that require sacrificing garden space, these side returns offer an excellent alternative with no compromise in outdoor area size or quality.

Contractor TypeLow-end EstimateHigh-end Estimate
Budget£52,000£75,000
Average£63,600£90,000
Premium£68,250£97,500

(for a 30 sqm extension)


Ground floor wraparound house extension average cost In London

If you’re longing for adequate space, a wraparound extension may be the ideal choice. Combining both a side return and rear expansion into one big L-shaped build, this development offers an abundance of room while consuming some portion of your garden area.

Contractor TypeLow-end EstimateHigh-end Estimate
Budget£78,750£112,500
Average£94,500£135,000
Premium£102,375£146,250

(for a 45 sqm extension)
For a bespoke quote call us on 0207 859 4225


Two-storey house extension average cost in london

Expanding your home on a single storey is one option for gaining more space, yet extending it over two stories can provide you with even greater possibilities. While this approach requires slightly more investment per square meter than the first alternative, its significantly larger size will increase the total cost substantially.

Contractor TypeLow-end EstimateHigh-end Estimate
Budget£78,750£112,500
Average£94,500£135,000
Premium£102,375£146,250

(for a 45 sqm extension)


Whole-house basement extension average cost In London

Basement extensions are an ideal extension option for properties in locations with high land values like London and other areas of the south. Despite being more costly due to the complications that come with excavating and constructing downwards, basement extensions provide a great way to expand your space without taking away from precious outdoor area.

Contractor TypeLow-end EstimateHigh-end Estimate
Budget£240,000£320,000
Average£288,000£384,000
Premium£312,000£416,000

(For a 80 sqm extension)
For a bespoke quote call us on 0207 859 4225


Glass extension average cost per square meter in London

Setting up a glass extension in your home could cost anywhere between £1,350 and £3,000 per square meter depending on the quality of finish. A more affordable option would be around £1,959 for an adequate end result while if you are looking to make a statement with luxury materials then it may set you back approximately £3,000 per square meter.


Conservatories and orangeries garden room extensions average cost in London

A standard conservatory garden room extension is much more budget-friendly, ranging from £10,250 to £16,750. On the other hand, an equally high-quality orangery could cost you between a staggering £30,000 to £35,000.


Flat pack extension average cost per square meter in London

If you are looking for affordable flat pack extensions, your best bet would be to budget around £750-£1,140 per square meter. For a mid-range option the cost could range from £1,275 to £1,800 and if you opt for luxury then expect to pay between £1,650 -£3,600 per square meter.


Semi-detached house extension average cost per square meter in London

If you’re considering a semi-detached house extension, rest assured that the cost is comparable to any other type of home addition. You may need to acquire a party wall agreement if your project involves a shared wall. The average price for such an undertaking ranges from £1,250 – £2,500 per meter square—a worthwhile investment for adding space and value to your property!
For a bespoke quote call us on 0207 859 4225