Development agency research into impact of new housing standards lays out worst-case scenario

New housing design standards for London could reduce the number of homes built in the capital by more than 2,400 a year, according to the London Development Agency (LDA).

The LDA last week published its updated version of the London Housing Design Guide, which will set standards for areas such as minimum size and bicycle parking provision.

Research carried out for the LDA by agent GVA Grimley, and published alongside the guide, says the space requirements could lead to 2,430 fewer homes being built on existing sites every year, as a worst-case scenario. It said the guide, part of mayor Boris Johnson’s crusade against “hobbit homes”, was “most likely” to mean between 240 and 1,220 fewer homes.

The research also found that the guide’s 73 stipulations would add between 3% and 16% to the build cost of new homes, depending on the type of dwelling, with apartments being worst affected. The study found the guide would increased the build costs on one development by £24,000 a unit.

This could be enough to make apartments uneconomic in some areas of the capital. It said: “There will be many instances where the viability is sufficiently robust … to be able to afford the requirements. However, in a number of cases, especially those where sale values are less than the average for London, the initial impact may be significant.”

Meeting the standard will be mandatory for homes receiving social housing funding from April 2011. Ultimately, all homes will be affected by the guidance as Johnson intends to incorporate the guide in the London Plan.

The guide rows back on some items in the 2009 draft, including that flats should have windows in more than one side, following protests from developers.

Tony Pidgley, the chairman of Berkeley Group, said the guide was “balanced” but that it did raise some viability concerns. “You need to spend £100m to get on site in London, so developers have to be allowed to offer a range of prodeucts,” he said.

The guide has been welcomed by architects, with the RIBA saying new standards were crucial.