Not all buildings and extensions require a Building Control application. Outlined below is the basic information on exemptions, although there can be other issues involving exemption. Therefore, it would be advisable in all cases to contact the Building Control Office to discuss your proposals.
• A detached single storey building having an internal floor area which does not exceed 30m2, which does not contain sleeping accommodation and is built largely of non-combustible materials, also it is not less than 1m from any boundaries.
• The extension of an existing building by the addition at ground level of a conservatory, porch, covered yard/way or a carport which is open on at least two sides, where the floor area does not exceed 30m2, and the addition is thermally separated from the main building.
It should be noted that whilst the construction of the building may be exempt, the electrical installations are not unless they are carried out by a competent electrician registered with one of the competent bodies approved by the Department for Communities and Local Government.
For further information please see the Planning Portal.