Two property consultancies say outdoor space should have a separate value to the rest of the home when it goes on the market.

DDRE says this is standard practice in Dubai, where the external space is priced at 50% of the average internal value for the equivalent square footage.

Knight Frank and DDRE Global says that demand for outside space in London is high amongst well-heeled international buyers, “many of whom are used to owning large homes with spacious rooms and large outside balconies and terraces.”

DDRE Global says that In the UK outside space is often considered on a general overview basis rather than adding a specific value to a property’s asking price. 

And the firm highlights one scheme – near the Lord’s Cricket Ground in north London – where each of the duplex penthouses has a minimum of 850 square feet of private terracing and roof gardens.

If London adopted the same pricing strategy as Dubai, this could represent up to £1.48m added to the already high price tag for each penthouse.

Benji Weinberger, an advisor at DDRE, says: “Outside space in London is massively important and yet severely undervalued by estate agents when putting an asking price to a property. Other countries like Dubai [sic] have a clearer way of valuing outside space whereas our British approach tends to be a more generic approach. Irrespective of price, some UHNW buyers simply won’t buy a property that doesn’t have substantial outside space, it has become a deal breaker.”