Within town growth zones, in addition to planned developments, unplanned development is encouraged by permitted development rules to allow e.g.
In addition Plot Passports allow owners to build additional dwellings on the land of existing buildings. They are issued by the local authority to all plots, and define parameters within which development is permitted such as daylight/sunlight, back to back distances, retention of valuable trees, appropriate materials, etc.
Within these limits property owners are free to develop provided there is an increase in dwellings. Adjacent plot-owners are encouraged to consider combining plots to maximise potential.