Paragraph 23

the building as extended or altered is to be used for purposes other than those of the undertaking concerned;

the building is to be used for a purpose other than—

the height of the building as extended or altered would exceed the height of the original building;

the floor area of the original building would be exceeded by more than 25% or 1,000 square metres whichever is the greater;

the external appearance of the premises of the undertaking concerned would be materially affected;

any part of the development would be carried out within 5 metres of any boundary of the curtilage of the premises; or

the development would lead to a reduction in the space available for the parking or turning of vehicles.

in the case of an industrial building, it shall only be used for the carrying out of an industrial process for the purpose of the undertaking or the provision of employee facilities;

in the case of a warehouse, it shall only be used for storage or distribution for the purposes of the undertaking or the provision of employee facilities;

it shall not be used to provide employee facilities between 7 pm and 6.30 am for employees other than those present at the premises of the undertaking for the purpose of their employment;

it shall not be used to provide employee facilities if a notifiable quantity of a hazardous substance is present at the premises of the undertaking.

the erection of any additional building within the curtilage of another building, whether by virtue of this class or otherwise, and used in connection with it is to be treated as the extension of that building, and the additional building is not to be treated as an original building;

where two or more original buildings are within the same curtilage and are used for the same undertaking, they are to be treated as a single original building in making any measurement.