• You want to make additions or extensions to a flat or maisonette (including those converted from houses). (But you do not need planning permission to carry out internal alterations or work which does not affect the external appearance of the building.)
   
• You want to divide off part of your house for use as a separate home (for example, a self-contained flat or bed-sit) or use a caravan in your garden as a home for someone else. (But you do not need planning permission to let one or two of your rooms to lodgers so long as the main use remains that of a private residence.)
   
• You want to build a separate house in your garden.
   
• You want to divide off part of your home for business or commercial use (for example, a workshop) or you want to build a parking place for a commercial vehicle at your home.
   
• You want to build something which goes against the terms of the original planning permission for your house - for example, your house may have been built with a restriction to stop people putting up fences in front gardens because it is on an "open plan" estate. Planning Service has a record of all planning permissions in your area.
   
• The work you want to do might obstruct the view of road users.
   
• The work would involve a new or wider access to a trunk or classified road.
  

You do not always need planning permission. It is not required, generally speaking, for changes to the inside of buildings, or for small alterations to the outside such as the installation of telephone connections and alarm boxes. Other small changes, for example putting up walls and fences below a certain height, may be considered as "permitted development" under the terms of the Planning (Northern Ireland) (General Development) Order 1993.

For more detailed information on when planning permission is needed see the
Householder Guide - Your Home and Planning Permission.