An Outline Planning Application is a way of seeking approval from a Local Planning Authority for the "development in principal" without actually specifying any of the specific detail.
The specifics are then sought to be approved via many seperate future planning applications, these are known as "Reserved Matters".
Usually this is often worded as "All matters reserved" or "All matters reserved apart from...."
Reserved matters can include items such as
"Access"
Accessibility to and within the site, for vehicles, cycles and pedestrians in terms of the positioning and treatment of access and circulation routes and how these fit into the surrounding access network.
"Appearance"
Aspects of a building or place within the development which determine the visual impression the building or place makes, including the external built form of the development, its architecture, materials, decoration, lighting, colour and texture.
"Landscaping"
Treatment of land (other than buildings) for the purpose of enhancing or protecting the amenities of the site and the area in which it is situated and includes: (a) screening by fences, walls or other means; (b) the planting of trees, hedges, shrubs or grass; (c) the formation of banks, terraces or other earthworks; (d) the laying out or provision of gardens, courts, squares, water features, sculpture or public art; and (e) the provision of other amenity features;
"Layout"
The way in which buildings, routes and open spaces within the development are provided, situated and orientated in relation to each other and to buildings and spaces outside the development.
"Scale"
Height, width and length of each building proposed within the development in relation to its surroundings.
There is a huge number of significant things that can be left vague in an outline planning application. Outline planning permission is a way for a developer or agent to determine if houses can be built on the piece of land, what exactly gets built is left until later.
From a developer / agents point of view, the more specifics there are in an Outline Planning Application, the more opportunities there are for a planning officer to find something they don’t like.
Outline planning permission is understandably popular with people and companies who want to sell on land to somebody else, often a major house builder.
Once Outline Planning permission is granted it massively increases the value of the land, often around 10 times the price. The land can then be sold without committing the new owners to constructing a specific type of house.
Too much detail in the outline application may limit the options of the future developer owner, too little detail may present too much uncertaintly in what could be approved.
After Outline Planning permission is granted, the developer / new owner normally has three years to apply for approval for the details (“reserved matters”). Within two years of the approval of the most recent reserved matter application, they will need to start constructon.