The Planning Act (Northern Ireland) 2011 sets out the definition of development so far as it relates to the purposes of the Act for Planning. It states at Part 3, Section 23
“Development is the carrying out of building, engineering, mining or other operations in, on over or under land, or the making of any material change in the use of any buildings or other land.”
It goes on to define building operations to include the demolition of buildings; rebuilding; structural alteration of or addition to buildings; and other operations normally undertaken by a person carrying on business as a builder.