23Substantial alteration—Act, s 29 (2) (a)

23 Substantial alteration—Act, s 29 (2) (a) (1) An alteration of a building is a substantial alteration if, during the 3 years immediately before the day the application for building approval for the alteration is made— (a) for a class 1 building—the total floor area of the proposed alteration, not including any internal alteration, is more than 50% of the floor area of the original building; and (b) for a class 2, 3, 4, 5, 6, 7, 8 or 9 building—the total floor area of the proposed alteration, including any other alteration, is more than 50% of the floor area of the original building. (2) However, neither refitting a building nor replacing the internal elements of the building is an alteration of the building unless the layout and function of the internal spaces of the building are changed. floor area, of a building, means the area of floor measured from the outer walls of the building, and includes the area on each storey of the building if there is more than 1 storey. Examples—effect of s 23 1 The floor area of a house is extended by 51%. The whole house must comply with the Act and the building code, not just the extension (see s (1) (a)), other than the parts of the building code that do not apply to the unaltered part of the house because of s 24. 2 A 40m2 sunroom is added to a building, adding only 10% floor area to the building. The sunroom must comply with the Act and the building code, but the rest of the building need not comply if no other floor area has been altered in the previous 3 years (see s (1) (a)). 3 A variety store and retail book shop (a class 6 building) are separated by a common wall in a shopping mall. The wall is removed to create a single larger room. If the room were to be used mainly for class 6 retailing, the only alteration is of an internal element, and the only alteration to the floor area is the addition of the floor area that was occupied by the wall. However, the room is converted for use as a carwash (making the building a class 8 building). Because of the change in function, the total floor area of the 2 shops and the floor area that was occupied by the wall have been altered for this section. The altered floor area is the floor area of the carwash. In the previous 3 years, other floor area alterations have taken place in the mall. These add up to 49.5% of the mall’s total floor area on all levels. The floor area alteration to create the carwash area takes the total to 50.1%. The whole mall must comply with the Act and the building code, not just the carwash. 4 A warehouse has no internal walls. A wall is built to divide the warehouse into 2 spaces. This does not amount to a substantial alteration if both of the divided spaces continue to function as warehouse space. However, if 1 of the divided spaces is to be used as a retail sales room, for this section the floor area of the space has been altered. If the floor area of the sales room and the area occupied by the wall is more than 50% of the total floor area of the warehouse, the change amounts to a substantial alteration and all of the warehouse must comply with the Act and building code. 5 A building contains a nightclub where a fire sprinkler system was installed 1 year ago. Plans now propose to upgrade the air-conditioning system and floor coverings throughout the building. As the work does not alter the floor area or function of the building it would not amount to a substantial alteration.