The Government's definition of brownfield land is set out in Planning Policy Statement 3: Housing (PPS3). This definition states that “previously developed land is that which is or was occupied by a permanent structure, including the curtilage of the developed land and any associated fixed structure”, so does include domestic gardens.
On 2 April 2009 the Government announced a review of evidence to establish whether there is a clear and genuine problem with the extent of housing development on garden land. We committed to considering action if the evidence confirms a problem, provided that any changes should not have the effect of undermining our objectives on housing. Our aim is to conclude the review and make a further announcement shortly alongside the publication of the findings and evidence.