Extending a City of London property would increase its value by £285,566 by square metre – the most across the UK, research from Leisure has found.
In second was Westminster (£36,030), followed by Camden (£36,030).
Outside of London homes in Broxbourne, Hertfordshire, are the most likely to have their value increased by an extension, with homes here being valued at £16,341 per square metre.
The bathroom and kitchen are the most popular rooms in the home for renovations, with 63% and 52% of homeowners having carried out renovations in the past 10 years respectively.
