Rear extensions which are exempt development are defined under Class One of the Second Schedule of The Local Government (Planning and Development) Regulations 2001.
- The area of the extension must not be greater than 40 meters squared, including all other extensions. The back garden must not be reduced below 25 meters squared.
- The walls of the extension do not exceed the wall height of the existing building.
- The height of the roof does not exceed the height of the existing roof.
- The extension must not extend out beyond the gable wall/s of the property.
- No exempt developments are allowed to be added to Protected Structures without first obtaining planning permission.
- Any extension to be built must not contravene any planning conditions for the property.
- The private open space in the Article 10 of the Planning Regulations also lists other works or developments that would have to be taken into account before considering if an extension / development is an exempt development.