What is the definition of 'building' according to the Building Code Act?

The definition of 'building' according to the Building Code Act encompasses a specific framework that includes basic requirements for what constitutes a building. The correct option refers to a structure that occupies over ten square metres and is characterized by essential components such as a wall, roof, and floor. This definition is comprehensive, as it also includes all associated plumbing and fixtures, indicating that a building must be a complete entity designed for use and occupancy.

The other choices do not capture the full essence of a building as defined by the Building Code Act. A temporary structure, for instance, does not meet the permanence or intended use typically associated with buildings covered by building codes. Similarly, a residential building of any size lacks the specificity needed, as the definition is not solely based on residential characteristics. Lastly, defining a commercial establishment purely by its size does not encompass all the structural and functional elements that a building entails according to the Act. Therefore, the correct answer reflects the comprehensive nature of what constitutes a building as outlined in the Building Code.