Britain’s builders have never been busier. Just as thousands of people have moved in the past couple of years in order to gain more living space, thousands of others have been extending their existing homes.
Our analysis shows that 28% of homes sold so far this year had been extended by the seller, adding an average of 25.9 square metres. This means that last year, homeowners extending added about 10 million square metres of floor space to the nation’s housing stock – a similar amount to that added by all the new homes sold by housebuilders in 2021.
We used the EPC register to compare the floor area of homes sold during the first quarter of this year to the floor area when they were bought – this allowed us to calculate how many properties have been extended, and by how much.
The size of extension varies. Some 12% of owners had enlarged their home’s original floor area by 10%, while 20% made their properties 20% bigger. About 9% of owners had doubled the size of their home during their ownership.
As you might expect, smaller homes are more likely to be extended than larger ones, which means that the average size of an extension is declining. Of the mid-terrace homes sold in the first quarter, 32% had been extended, rising to 35% for end-of-terrace properties. Some 28% of flats had been enlarged but this fell to only 16% for detached houses.
The amount of value added by an extension varies significantly depending on location – in places where people boost their house price the most, they are most likely to extend.
Of the London homes sold this year, 36% had been extended by an average of almost 22 square metres. The capital is also where homeowners can add the most value to their home by enlarging their property – after build costs, a Londoner made an average “profit” of £56,000, representing a 57% uplift on the money spent on the works.
In the South East of England, 30% of homes had been extended, with owners making a profit of almost £33,000 and seeing a 32% uplift on their outlay. Some 29% of homeowners in the East who extended made an average profit of £10,414 (an 11% uplift) but the gains fell to £3,052 for those in the South West (who saw a house price uplift of only 5%), and to £2,150 for owners in Wales (who boosted their home value by just 2% and were least likely to extend).
In the West Midlands, however, owners who extend only just make a profit after costs and boost their house price by 2%. In the East Midlands, the average extension adds no value, while in the North West, North East and Yorkshire and Humberside, property owners could potentially lose money if they added an extension.
To make these profit calculations we assumed an average build cost for the extension of £350 per square foot (£3,770 per square metre), with the figure being a little higher in the south and lower in the north. The lesson here, is that while historically there’s money to have been made by extending a home in the South of England, the sums haven’t always stacked up for properties further North.
