The rules on permitted development, set out in Schedule 2 of the Order, are subdivided into a series of Parts. Understanding these parts is essential for knowing what you can build without planning permission.

Part 1 - Development within the curtilage of a house

This Part specifically deals with development within the curtilage of a house. Part 1 is then sub-divided into Classes covering various types of development:

Class A - the enlargement, improvement or alterations to a house such as rear or side extensions as well as general alterations such as new windows and doors. There is a neighbour consultation scheme for larger rear extensions under Class A.
Class B - additions or alterations to roofs which enlarge the house such as loft conversions involving dormer windows.
Class C - other alterations to roofs such as re-roofing or the installation of roof lights/windows.
Class D - the erection of a porch outside an external door.
Class E - the provision of buildings and other development within the curtilage of the house.
Class F - the provision of hard surfaces within the curtilage of the house such as driveways.
Class G - the installation, alteration, or replacement of a chimney, flue or soil and vent pipe.
Class H - the installation, alteration, or replacement of microwave antenna such as satellite dishes.

Part 1 covers most common home improvements including extensions, loft conversions, and outbuildings.

Part 2 - Minor Operations

This Part of the permitted development order relates to minor operations:

Class A - The erection, construction, maintenance, improvement or alteration of a gate, fence, wall or other means of enclosure.
Class B - means of access to a highway.
Class C - exterior painting.
Class D - electrical outlet for recharging vehicles.
Class E - electrical upstand for recharging vehicles.
Class F - closed-circuit television cameras.

Understanding these classes helps you determine what work you can carry out without needing to apply for planning permission. However, it's always advisable to check with a professional as there may be local restrictions or Article 4 directions that remove certain permitted development rights.