If you are going to build an extension or make other changes to your house in Ireland, you may need planning permission. Generally minor changes such as those listed below do not need planning permission but you should always make absolutely certain that you don't need planning permission before you start building. Failure to obtain planning permission where it is required can result in penalties (i.e., significant fines or even imprisonment). Your local authority will be able to advise you about this.
Generally, you will not need planning permission for:
Building an extension to the rear of the house which does not increase the original floor area of the house by more than 40 square metres and is not higher than the house. The extension should not reduce the open space at the back of the house to less than 25 square metres which must be reserved exclusively for the use of the occupants of your house. If your house has been extended before, the floor area of the extension you are now proposing and the floor area of any previous extension (including those for which you previously got planning permission) must not exceed 40 square metres. (There are also other height restrictions.)
Converting a garage attached to the rear or side of the house to domestic use so long as it has a floor area of less than 40 square metres. Building a garage at the back or side of a house so long as it does not extend out in front of the building line of the house and does not exceed four metres in height (if it has a tiled/slated pitched roof) or three metres (if it has any other roof type). This building will be exempt from planning permission once the floor area is limited to 25 square metres. Garages or sheds to the side of the house must match the finish of the house and may not be lived in, used for commercial purposes or for keeping pigs, poultry, pigeons, ponies or horses.
Building a front porch so long as it does not exceed two square metres in area and is more than two metres from a public road or footpath. If the porch has a tiled or slated pitched roof, it must not exceed four metres in height or three metres for any other type of roof.
Capped walls made of brick, stone or block, wooden fences but not security fences can be erected as long as they do not exceed 1.2 metres in height or two metres at the side or rear. Gates may be build provided they do not exceed 2 metres in height. Permission is always required to if you wish to widen or create new access to the public road.
A central heating system chimney, boiler house or oil storage tank (up to 3,500 litres capacity).
Car parking spaces, garden paths etc
A TV aerial on the roof so long as it is less than six metres higher than the roof
A satellite dish (up to one metre across the below the top of the roof) at the back or side of the house (a dish on the front needs planning permission). Only one dish may be erected on a house.