Variations (or Change Orders) in construction projects are common and there is not likely that a project completes without any variation. However, variations are a nightmare for the owners, generally, although there are negative variations which lower the total cost of a project.
Variations are caused due to few reasons which are;
Lack of consistent contract documents
Change of regulations,
Additional requirements by the owner
Cancellation of items
Failure to address discrepancies in a timely manner
Variations are governed by the relevant clauses in Conditions of Contract.