Eighteen percent of all new homes built in the UK are built on residential land, up from 11% a decade ago.
(Homes are springing up in people's gardens as the property boom continues. This is called "garden grabbing", where developers buy a house with a big garden, apply for planning permission to demolish the house and build either flats, or even a mini-estate in its place. Property in the UK has gone crazy, and it's not sustainable.)