Renovations: how much will an extension add to the value of your house?

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Lizzie Rivera18 October 2017

A calculator has been released to help owners estimate how much value building an extension will add to their home.

The calculation is based on the latest Office for National Statistics (ONS) figures measuring the average cost of a property per square metre – an area about the size of a red phone box – in each local authority in England and Wales.

The report reveals that a medium-sized extension of 25 square metres currently adds an average of £59,000 to a property price.

However, this increases to more more than £169,000 in areas of London such as Hackney and Richmond, where the gulf in prices between two-bedroom flats and three-bedroom houses makes it almost impossible for owners to upsize.

The estimations are only a guide — the actual value of an extension will also depend on the quality of the construction, what type of room the extension houses and the exact location of the property within a local authority.

"Space is always the most sought-after commodity when house hunting, but it's important to remember that the cost of an extension won't always translate into the same monetary value for the property as a whole," says founder of eMoov.co.uk, Russell Quirk.

"In a major city where space is tight a loft extension can add real value, but outside of the city where there is an abundance of space, this isn't always the case."

THE AVERAGE COST OF A PROPERTY IN ENGLAND & WALES

Unsurprisingly, areas in London are the most expensive in England and Wales.

One square metre of floor space costs more than £20,000 in Kensington and Chelsea. In Blaenau Gwent in the South Wales valleys, the same amount of space costs £777.

Parts of the South East and South West have the next most expensive areas per square metre after London.

Prices in Harrogate, York and Trafford are among the most expensive in the North of England.

Working out a property's price per square metre may not tell the whole story when it comes to assessing a house's value but it can be a useful way of comparing the affordability of different areas.

"It is essentially a toe dip indicator into the affordability of an area as an average asking price is just that, a price," says Quirk.

Whereas £300,000 may buy you a two-bedroom flat in Harrow, it can buy you a three-bed semi-detached house in Newcastle."

Find out how much value an extension could add to your home with the ONS calculator.